Urban ecology of Drosophila suzukii

Romain Ulmer, Aude Couty, Patrice Eslin, Françoise Dubois, Emilie Gallet-Moron, Nicolas Lamotte, Justine Pavis, Alice Samama, Fabien Spicher, Olivier Chabrerie

► To cite this version:

Romain Ulmer, Aude Couty, Patrice Eslin, Françoise Dubois, Emilie Gallet-Moron, et al. Urban ecology of Drosophila suzukii. Urban Ecosystems, 2024, 27, pp.983-2004. 10.1007/s11252-024-01554-w. hal-04643014

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Urban ecology of *Drosophila suzukii*

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Romain ULMER, Aude COUTY, Patrice ESLIN, Françoise DUBOIS, Emilie

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GALLET-MORON, Nicolas LAMOTTE, Justine PAVIS, Alice SAMAMA, Fabien

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SPICHER & Olivier CHABRERIE*

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EDYSAN, UMR 7058 CNRS, Université de Picardie Jules Verne, 1 rue des Louvels, 80037

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Amiens Cedex 1, France; Phone: +33 (0)3 22 82 78 79.

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* corresponding author: olivier.chabrerie@u-picardie.fr

<figure><img src="image_2.png" /></figure>

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**How to cite this article**: Ulmer R., Couty A., Eslin P., Dubois F., Gallet-Moron E., Lamotte

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N., Pavis J., Samama A., Spicher F. & Chabrerie O. **2024**. Urban ecology of *Drosophila suzukii*. *Urban Ecosystems*. Vol. 27: 1983–2004. https://doi.org/10.1007/s11252-024-01554-

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15 **Abstract**

16 **Context**

17 Urban environments are vulnerable to the introduction of non-native species and sometimes
18 contribute to their invasion success. Knowing how urban landscape features affect the
19 population dynamics of exotic species is therefore essential to understand and manage these
20 species.

21 **Objective**

22 The spotted wing drosophila, *Drosophila suzukii*, is a highly polyphagous fruit fly that has
23 become a very problematic invasive species over the last decade. Because of its important
24 damage on fruit production, *D. suzukii* populations have mainly been studied in agricultural
25 areas, while their dynamics in urban landscape remain poorly explored. The objective of this
26 study was to investigate the role of urban environment in the invasion success of *D. suzukii* by
27 identifying local and landscape factors driving the abundance of the fly along seasons and
28 urbanization gradients.
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29 **Methods**

30 To achieve this, 526 insect traps were randomly set in four different habitats (urban forest,
31 park, riverside and town centre) along an urbanization gradient in the city of Amiens (France),
32 between September 2018 and August 2019. The influence of landscape and local
33 environmental variables on Drosophilidae species diversity and composition was examined
34 using GLM and multivariate analyses.
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35 **Results**

36 We found that Drosophilidae species richness and abundance were negatively impacted by
37 urbanization. The Drosophilidae community was dominated by *D. subobscura* and *D. suzukii*,
38 but their relative abundance varied with seasons. *Drosophila suzukii* used urban forest during
39 winter and also during heat waves in summer. The fly was still active in this habitat in winter
40 when the ground was covered with snow. The cover of brambles, shrubs, soil litter and dead wood debris were identified as valuable ecological indicators of the presence of *D. suzukii*

42 **Conclusion**

43 We highlight the role of the different components of urban environment in the ecology of *D. suzukii*, particularly with regard to its winter survival. These results could serve for designing management strategies in urban habitats in order to reduce the invasion success of *D. suzukii*.

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47 **Keywords:** Urban landscape, biological invasion, spatial and temporal patterns, spotted-wing drosophila, exotic insect pest, insect diversity

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**Introduction**

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Urban environments offer very specific and harsh living conditions for organisms (Gilbert 1989; Fattorini 2011) and are often pointed as ‘a special case’ compared to other environments (Walbridge 1997). Most urban areas are highly artificialized in terms of building density, road traffic (Martin et al. 2018) and artificial night-time light (Owens and Lewis 2018); they are intimately close to human activities (Thomas et al. 2017) and generally warmer compared to adjacent rural areas (Oke 1973; Meineke et al. 2017). Artificial lights notably affect insect populations. These man-made environments harbor specific biodiversity (Raupp et al. 2010), and their importance in ecological studies has grown in the last two decades (McDonnell and Hahs 2008). Indeed, more than half of the world’s human population lives in cities and the percentage of land used as urban areas has been growing at a quick rate (United Nations, 2018), at the expense of less artificial environments. Studies have shown that among the species living in urban areas, insects show a non-negligible diversity (Sattler et al. 2010). This includes native species that can find in cities resources and/or shelter that become scarce in rural areas (Garcia et al. 2008; Unterweger et al. 2018), but also exotic and/or invasive species that also benefit from these favorable conditions (Garcia et al. 2012; Gaertner et al. 2017; Gentili et al. 2024) or rapidly adapt to urban constraints such light at night (Sato and Takahashi 2022). Urban areas can then become key places in the invasion success of certain species (Padayachee et al. 2017).

Among those invasive species, one has become very problematic during the last decade, the spotted wing drosophila, *Drosophila suzukii* (Matsumura 1931). This fruit fly is an invasive pest native to Southeast Asia. It was first spotted in 2008 in Europe (Cini et al. 2014) and North America (Walsh et al. 2011), where it spread rapidly. It also spread to Central and South America where it was first spotted in 2013 and more recently in Africa
(2013 in Morocco and La Réunion, and 2019 in Kenya; https://gd.eppo.int/taxon/DROSSU/distribution). This highly polyphagous species infests a wide variety of wild fleshy-fruited plants (Kenis et al. 2016; Poyet et al. 2015), including invasive (Poyet et al. 2014) and toxic ones (Poyet et al. 2017), as well as cultivated species (Lee et al. 2011) causing important damages on agricultural production with considerable economic impact (Asplen et al. 2015; Yeh et al. 2020). Given the rapidity and the amplitude of its spread, understanding the causes of its invasion success is important to predict the future of its distribution.

As a consequence of their damage caused on crops, *D. suzukii* populations have been mainly studied in agricultural landscapes and in natural habitats in the vicinity of farms and fruit crops (Tonina et al. 2018; Santoiemma et al. 2018; Delbac et al. 2020; Ulmer et al. 2022). Studies on the role played by cities and peri-urban areas in its invasion process are rare (Bombin and Reed 2016; Sato and Takahashi 2022). These works showed a significant correlation between land use and abundance (but not diversity) of drosophila species in Alabama and suggest that invasive drosophila such as *D. suzukii* could dominate the drosophila communities in urban environments. Lab studies also showed that environmental factors characteristic of cities (higher temperature and light at night) could trigger evolutionary and plastic responses of *D. suzukii* in terms of thermic tolerance and diurnal activity. Urban landscapes are vulnerable to the introduction of non-native species (Branco et al. 2019) and invasions are even more common in urban conditions than in rural conditions (Spence and Spence 1988). In Europe, and particularly in France, most of the first records of *D. suzukii* were made in urban areas such as parks (Calabria et al. 2012). Moreover, the dispersal of *D. suzukii* as well as other drosophila species follows commercial fruit trafficking routes (Cini et al. 2014; Lavrinienko et al. 2017; Estay et al. 2023) ending in urban areas.
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Therefore, studying the ecology of *D. suzukii* in cities seems crucial in understanding how these environments shape the populations of the pest and affect its persistence.

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Urban areas are not homogenous landscapes. Although cities are characterised by a prevalence of built surfaces, they remain mosaics of habitats with varying quality and constraints for insect populations. These habitats may offer both shelters with suitable conditions and trophic resources for insects (New 2015). Urban areas could be important for *D. suzukii* as they may provide frost-free shelters and become refuges during winter (Unterweger et al. 2018). Indeed, despite various studies on the subject, the way *D. suzukii* overwinters is still not fully understood (Panel et al. 2018). Insects commonly migrate to more protected areas to reduce the risk of freezing to death (Leather et al. 1995). As temperatures inferior to -7°C are lethal for *D. suzukii* (Jakobs et al. 2015), cities, through the “heat island effect” (Oke 1973; Meineke et al. 2017), could represent a potential underestimated reservoir of the pest during the cold season. Nevertheless, the same urban heat islands may also represent a risk for the fly during the summer.

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Variations in insect diversity and abundance in cities are often linearly structured along a main gradient of urbanization (Bennett and Gratton 2012; Bombin and Reed 2016; Tzortzakaki et al. 2019). On the one hand, mineral and impervious surfaces such as buildings, roads and other paved areas (parking lots, etc.) lack both food resource and shelter, and appear to be inhospitable for organisms. As a response, insect diversity generally increases from the town centre toward peri-urban areas (Geslin et al. 2016; Tzortzakaki et al. 2019; Fenoglio et al. 2021). On the other hand, parks, garden, hedgerows and grass strips may offer interesting features for insects feeding and reproducing (Beninde et al. 2015; Hall et al. 2017; Theodorou et al. 2020). Despite being often heavily anthropized and frequently disturbed, they generally offer a variety of fruit plants, shelters and man-made food (from human litter). Some ornamental plant species frequently found in city parks and green spaces bear fruits
earlier than most wild species (e.g. *Aucuba japonica*, *Elaeagnus* sp., *Symphoricarpos* sp., Poyet et al. 2015). Private gardens can show a great variety of habitats and often contain cultivated fruits such as cherry, strawberry, raspberry, highly infested by *D. suzukii*. Even if they are smaller than parks, gardens are frequent and distributed throughout the cities, making them ideal stepping stones to connect larger patches of vegetation such as parks and green areas (Goddard et al. 2010). Urban forests are also hot spots of insect diversity in cities (New 2015) and forests are commonly used by *D. suzukii* (Poyet et al. 2014) and promote fruit infestation by the fly (Ulmer et al., 2022). Most of the big cities are historically funded and expand along rivers because of their role as water supply and transport routes of goods by boat (Kondolf and Pinto 2017). Water bodies present within the cities, such as rivers or ponds, are often associated with increased atmospheric humidity and an air cooling effect (Murakawa et al. 1991; Hathway and Sharples 2012), both of which can be interesting for insects during the summer (Cregg and Dix, 2001; Kenneth, 1932). This may be particularly true for *D. suzukii*, which populations are moving closer to river streams in the hot season (Maceda- Veiga et al. 2021).

The goal of this study is to better understand the role of urban environment in the invasion success of *D. suzukii* and its place within the Drosophilidae communities of different urban habitats. Using a rather holistic approach combining Drosophilidae community, plant community, landscape ecology and meteorology, we aimed at identifying environmental biotic and abiotic factors driving the variations in the abundance of *D. suzukii* across seasons and habitats in urban areas.

More specifically, we sought to determine (1) what kind of urban habitats are favoring the persistence of *D. suzukii* during the year, and especially during the winter season, (2) what is the place (dominant core or satellite species; Deconninck et al. 2024) of *D. suzukii* within the Drosophilidae communities of urban habitats along seasons and (3) what are the effects of
environment constraints and resources availability on the distribution and life history traits of the species. To achieve this, insect trapping campaigns were conducted for an entire year in the city of Amiens, in the North of France. A total of 526 traps were placed at ten times in 4 different urban environments along an urbanization gradient. These four selected environments, an urban forest, a recreational park, the banks of the Somme river, the town centre, were also chosen because they (i) were representative of the main contrasting features characterizing the urban landscape of the city of Amiens and (ii) represented different types of potential trophic sources (in terms of wild fruit composition, for example) or shelters (vegetated shelters versus anthropogenic shelters).

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## 160 Materials and methods

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162 *Study habitats and sampling design*

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The study was conducted in Amiens (Somme, France, 49°53′40″ N, 2°18′07″ E), in a metropolitan area of around 160,000 inhabitants. The city of Amiens is moderately urbanized, with 42.6% of urbanized land cover and 13.7% of industrialized areas and road cover (Corine Land Cover database, 2018) leaving space for various forms of vegetated areas (parks, green spaces, wooded areas, agricultural areas). The city is also located along the channelled Somme River, highly ramified and meandering within the urban area. The insect trapping was conducted in four different habitats along an urbanization gradient (Figure 1): (i) An urban forest (FOREST), a wooded area with a dense tree cover dominated by *Acer pseudoplatanus*, *Fraxinus excelsior* and *Ulmus minor* colonized by the liana *Hedera helix*, in the border of the city (extending between Gutenberg road and Le chemin de Longpré, Amiens). (ii) The Saint-Pierre Park (PARK), a major artificialized green space composed of a mix of exotic
ornamental plant species and spontaneous or planted local species. The park is a mosaic of open wooded and grassland areas organized around playgrounds and walking path for families. It also contains concrete roads, buildings and several water bodies (pond, small channels). (iii) The banks of the Somme river (RIVER) meandering within the city and bordered by a hygrophilous vegetation. (iv) The centre of the city of Amiens (TOWN) is organized around the Cathedral and dominated by roads and buildings (>76% of the land cover, Figure 1). The four types of trap locations are characteristic of four urban landscapes dividing the city (a wood-dominated area, recreational green park, river-influenced area, and densely built centre) and their features are shown in Figure 1.

Between September 2018 and August 2019, nine trapping campaigns were organized to cover an entire year (dates of residence of traps in the field: 20th-27th September, 11th-18th October, 15th-22nd November, 6th-13th December, 29th January-5th February, 19th-26th Mars, 6th-13th May, 1st-8th July, 22th-29th August). For each campaign, 15 traps were randomly placed in each habitat (giving 60 traps per campaign and 540 traps for the entire study). The 60 traps were placed in the field on the same day and collected after seven days of residence. The locations of the traps were different in the different sampling periods. Fourteen traps out of the 540 were damaged during the whole sampling campaign (due to extreme wind events or human alterations) and were not considered in the analyses.

Additionally, we also sampled the drosophila species in fruit stores and in houses, where commercial fruit were present (i.e. mainly in the kitchen rooms of houses where fruit are stored between meals) using a total 139 traps and the same protocol as for other habitats. Nevertheless, given the extremely low abundance of *D. suzukii* in fruit shops and houses the results were shown in Supplementary Material (Supp. Mat. A).

### *Drosophilidae species collection*
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Insect traps were made using the lower half of a red plastic bottle (Badoit ®; Firlej and Vanoosthuyse 2017; Weydert et al. 2016), as red has been proved to be the optimal color for traps design (Renkema et al. 2014). The traps were 130 mm high and 85 mm in diameter. As traps with a side entry catch more individuals (Lee et al. 2013), five holes (Ø 5 mm; Hamby, et al. 2014) were drilled on the sides of traps at a distance of 70 mm from the bottom. The tops of the traps were covered with transparent plastic wrap to protect its content from rain and ease its collect. Before placing them on the field, the traps were filled with an attractive solution composed of apple cider vinegar (80 mL) and liquid cane sugar (20 mL) (Burrack et al. 2015; Lasa et al. 2020), with the addition of a drop of dish soap to break the surface tension (Lee et al. 2013). They were then hung at a height ranging from 1 m to 1.5 m.

After collecting the traps, their content was filtered and kept in a 70% ethanol solution. Using a Leica M205C stereomicroscope, the taxa of the Drosophilidae family were identified to the species level using Bächli, Viljoen, Escher, & Saura (2005) identification keys and the collection of standard specimen from the laboratory. *D. suzukii* individuals were sorted and kept in alcohol for further measurements.

*Morphs description and wing size measurement of Drosophila suzukii*

*D. suzukii* individuals were counted, sexed, and divided into three morph categories (Panel et al. 2018). Individuals with a clear yellowish colour except for the last three dark tergites were classified as summer morphs. Individuals with mainly dark tergites but a clear pronotum were classified as intermediate morphs. Finally, individuals with dark tergites and pronotum were classified as winter morphs (Supp. Mat. B).
Wing dimensions are often used as an index of body size in *Drosophila* sp. (Misra and Reeve 1964; Sokoloff 1966; Huey 2000). For each trap, the wings of up to 5 males and 5 females *D. suzukii* were randomly selected and measured. To do so, the right wing of the individual was removed and flattened between two microscope slides. Measurements were made with a Leica M205C stereomicroscope equipped with a Leica MC170 HD camera and the software Leica Application Suite, following the protocol used by Gilchrist et al. (2001) on *Drosophila subobscura*. Wing length was calculated by adding the length of two segments along vein IV, L1 (from the base of the fourth longitudinal vein to the posterior cross vein) and L2 (from the posterior cross vein to the distal end of the fourth longitudinal vein). The wing width W, was measured as the distance from the distal end of the fifth longitudinal vein on the trailing edge of the wing to the leading edge in a line perpendicular to the vein III. A wing area index was then calculated using the formula: Wing Area Index = (L1 + L2) x W. Intermediate wing measurements (L1, L2, W) were used to build the integrative Wing Area Index and were not further used given their inherent redundancy with the index.

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Plant community characterization
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Around each trap, a vegetation survey was done within a 5 m-radius plot on the day of trap setting in the field. The cover of vascular plant species was estimated for each vegetation layer: herbaceous layer (<1 m), shrub layer (1-8 m), tree layer (>8 m). If fleshy fruits were present within a 10 m radius, the identity of their species was recorded. Plant species were identified following Lambinon (2004).

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Local, landscape and meteorological variables
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The environmental conditions of each trap locality were characterized using a set of local, landscape and meteorological variables. Within each 5 m-radius plots, the cover of tree layer, shrub layer, herbaceous layer, dead wood debris, leaf litter, waste container, river, road, building and trail was estimated (see the list of variables in Supp. Mat. C).

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A geographic database was created using a Geographic Information System (GIS; ArcGIS Pro v.2.5, ESRI) to build maps of the landscape surrounding traps. The traps were positioned in the GIS and buffers of 100 m radius around each trap were created for subsequent analyses of landscape composition. This radius was chosen as a previous study showed that *D. suzukii* has a relatively low dispersal capacity, with a daily flight distance of less than 100 m (Vacas et al. 2019). Moreover, in a previous study, we showed that fruit infestation rates by *D. suzukii* responded to natural habitat cover in a 100 m radius around sampling sites (Ulmer et al., 2022). Landscape elements (wood, grass strip, grassland, hedgerow, crop, private garden, building, water, trail, road, bare soil) were extracted from the OSO database (Scientific Centre of Expertise OSO, 2018), updated by field observations and integrated to the GIS database. For each trap, the percentage of cumulated area of polygonal elements composing the landscape were then computed in the 100 m buffer.

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The daily meteorological data between the first day of the year of trapping (01/01/2018 or 01/01/2019) and the day of trap collection were retrieved from the nearest meteorological station (https://www.historique-meteo.net/france/). The average distances from the traps to the nearest meteorological station were 18.70, 17.69, 17.39 and 17.28 km for forest, park, riversides and town centre, respectively. Daily minimum, mean, and maximum temperatures, as well as precipitation, were extracted for each day from January 1st. This allowed us to calculate the following variables from the beginning of the year to the day the traps were collected as well as during the 7 days of trapping: mean daily minimum temperatures, mean daily maximum temperatures, mean of daily mean temperatures, number

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of frost days, cumulative temperature (degree-days). Degree-days were calculated using a lower threshold of 0°C between January 1st and the day of sampling (Baskerville and Emin 1969). The baseline value of 0°C is a standard threshold commonly used in insect and plant studies (White et al. 2012; McNeil et al. 2020). This threshold is particularly adapted to study the temporal variations of fly populations (Iler et al. 2013) and was also chosen as we observed and captured *D. suzukii* individuals in activity at very low temperature (close to 0°C) during winter days (Ulmer et al. 2022). Mean and cumulative rainfall between January 1st and the day of sampling, as well as during the 7 days of trapping, were also calculated.

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283 *Data analyses*

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The influence of environmental factors (local biotic and abiotic conditions, landscape composition and meteorological variables; see the list in Supp. Mat. C) on the species richness of Drosophilidae community (SRdroso), the number of Drosophilidae individuals (ABUNdroso), the number of *D. suzukii* individuals (DSabund), the number of summer (DSEstivale) and dark (DSInt_Hiver) morphs of *D. suzukii* and the mean wing size of female (WINGfem) and male (WINGmal) *D. suzukii* per trap was tested using general linear models (GLMs). The variables were checked for normality and transformed (log₁₀+1) when necessary prior to analyses (Quinn, & Keough, 2002). To avoid overfitting and for model simplification, only environmental variables the most significantly correlated with response variables (with R > 0.2, Pearson correlation) were considered in the models. A backward selection of explanatory variables and the Akaike information criterion (AIC) were used to select the most parsimonious model, *i.e.* the most significant model with the lowest AIC (Harrison et al. 2018). The homoscedasticity of residuals from the models was checked using biplots and model predictions. The effect of habitat on log₁₀+1-transformed Drosophilidae species
richness (number of species per trap) and species abundance (number of counted individuals per species per trap) was examined using mixed models (GLMMs) using habitat as explanatory factor (4 categories: forest, park, riverside, town centre). In these models, the sampling month was introduced as a random effect term to account for the effect of seasonal sampling. The differences in wing size (Wind Area Index) of *D. suzukii* individuals between morphs and between habitats were assessed using ANOVA. Post-hoc comparisons of means were performed using Tukey's honestly significant difference (HSD) test.

Multivariate analyses were used to examine the influence of environment on Drosophilidae species composition following the general recommendations of McCune and Grace (2002). First, a detrended correspondence analysis (DCA) (Hill and Gauch 1980) was ran on Drosophilidae species frequency matrix (482 traps x 25 Drosophilidae species) to decide (on the basis of the gradient lengths depicted by DCA axes) whether the linear or unimodal model was more appropriate in the subsequent multivariate analyses. Sampling plots with no Drosophilidae species in the trap were not considered in the species matrix (i.e. 44 traps out of the 526 were removed from the analysis) and the Drosophilidae species matrix was log₁₀+1-transformed prior to analyses so as to decrease the influence of extremely large numbers of individuals (Baar and ter Braak 1996). DCA results on species matrix showed short gradients (< 4 S.D.), suggesting that an ordination technique based on the linear model, such as redundancy analysis (RDA), could be used (Jongman et al. 1995). On the basis of these results, a RDA of Drosophilidae species matrix (482 traps x 25 Drosophilidae species), constrained by environmental variables (482 plots x 31 environmental variables) was performed to examine the response of Drosophilidae species composition to environment. To avoid multicollinearity among the numerous meteorological variables, only cumulative temperature (TEMCCUM), cumulative precipitation (CUMRAIN) and number of frost days (NFROST) measured at the year scale and during the week of sampling were considered in
the RDA. The first axis of the RDA was rotated by *D. suzukii* frequency in order to improve
ease of interpretation of the constellation of plot and environmental gradients from the angle
of the dominance of *D. suzukii* (Peck 2016). Finally, a second RDA was processed to assess
the relationships between Drosophilidae species community (374 traps x 25 Drosophilidae
species) and vascular plant species community (374 plots x 132 plant species from three
vegetation strata), following the same procedure as above. In this last RDA, plots from the
town centre with no spontaneous plant community and other plots with no plant species were
not considered and plant species present in less than 2% of the sampling plots were removed
from the matrix prior to analysis. To identify plant species indicator of the presence of *D.
suzukii* along seasons, for each sampling date, Spearman correlations were calculated between
the abundance of *D. suzukii* in traps and the cover of the plant species selected in the last
RDA (i.e. plant species present in more than 2% of the sampling plots).

Univariate analyses were performed with IBM-SPSSv.24.0 (IBM, Armonk, NY, USA)
and multivariate ones with PC-ORD v.7.03 (McCune and Mefford 2016).

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339 **Results**

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341 *Drosophilidae species abundance and richness*

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A total of 91397 individuals belonging to 25 Drosophilidae species were collected in
526 traps (Table 1). Drosophilidae community was largely dominated by two species,
*Drosophila subobscura* (45.33% of the individuals, a mean of 78.77 individuals per trap) and
*Drosophila suzukii* (38.35%, 66.61 individuals per trap). These species sometimes had a very
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high local population abundance, with a maximum of 2422 individuals of *D. subobscura*
counted in a single trap in forest in May and 1565 individuals of *D. suzukii* in a single trap in
urban park in September. Only four other Drosophilidae species, *Drosophila immigrans*,
*Drosophila kuntzei*, *Drosophila phalerata* and *Drosophila melanogaster*, reached values of
relative abundance above 1% of the total individuals of the study.

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The distribution patterns of Drosophilidae species were contrasted between habitats
and seasons. *D. subobscura* and *D. suzukii*, were highly represented in urban forest with
respective means of 166.14 and 117.16 individuals per trap (Figure 2 and Supp. Mat. D). *D.
subobscura* was permanently present in forest and park (Supp. Mat. E) but showed population
peaks in wooded habitat mainly in spring and autumn (Supp. Mat. F). *D. suzukii* mainly
occurred in urban parks in autumn, took refuge in the forest during the cold season from
November to March, and used riversides in spring and summer (Figure 3). Its peak of
abundance was in September and an important increase of trapped individuals was noted in
December (Supp. Mat. F), probably caused by an ephemeral warming during the sampling
week (Supp. Mat. F). Urban forest was also the preferred habitat of *Drosophila kuntzei*,
*Drosophila immigrans*, *Drosophila phalerata*. *Drosophila phalerata* left the forest for the
riversides from September to November. *Drosophila melanogaster* was more represented
along the riversides and in the town centre and *Drosophila hydei* in urban parks (Supp. Mat.
E). Among the 139 traps placed in fruit stores and houses, we only collected 24 individuals of
*D. suzukii*, which was only present in 7 traps (Supp. Mat. A). It corresponds to 1.6% of the fly
abundance in stores and houses. Given this extremely low abundance of *D. suzukii* in fruit
shops and houses (for comparison, 1565 individuals of *D. suzukii* were counted in a single
trap located in urban park in September) the results were shown in Supp. Mat. A. Fruit shops
and house rooms containing fruit were dominated by *Drosophila melanogaster* (67.83% of
the trapped individuals) and *Drosophila hydei* (18.69%).

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Drosophilidae species richness averaged 4.06 ± 0.13 species per trap in the whole study (n=526 traps) and was significantly different between habitats (F = 72.496; p < 0.001 between pairs of habitats) with a maximum in forest habitat and a minimum in the town centre (Figure 4a). A similar variation pattern was observed for Drosophilidae abundance (mean = 173.76 ± 13.20 individuals per trap) with a decreasing number of Drosophilidae individual following the urbanization gradient, from the most natural to the most anthropized habitats (F = 39.062; p < 0.001 between habitats; Figure 4b). Numerous environmental variables influenced Drosophilidae species abundance and diversity (GLMs, Supp. Mat. H). Drosophilidae species richness increased with local cover of tree and shrub and decreased with local building density, water in the surrounding landscape and extremely low temperature during the sampling week. The total abundance of Drosophilidae individuals in traps increased with variables related to natural habitats, such as tree and shrub species richness, shrub cover and wood debris, and decreased with urbanization (BUILD, loROAD) and frost events. The abundance of *D. suzukii* followed this trend, increasing with local shrub cover and wood debris and with wood cover at the landscape scale, while decreasing with road and building density (GLM, Supp. Mat. H). It should be noted that the number of fruit-bearing plant species (NFRUIT) surrounding traps promoted *D. suzukii* populations. The presence of waste did not significantly influence *D. suzukii* abundance in traps (R=0.022, p=0.616). Cumulated rain during the sampling week reduced the number of *D. suzukii* individual (variable RAINCUMw, Supp. Mat. H), while high temperatures (TEMTOP, Supp. Mat. H) were favourable to their abundance in the traps.

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Effect of environment on Drosophilidae community composition

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In the redundancy analysis (RDA) coupling environment and drosophilidae species matrices (Figure 5), the eigenvalues of the first two ordering axes explained 38.4% of the data variance (axis 1 = 22.5%, axis 2 = 15.9%, Monte Carlo test: p ≤ 0.05). In the ordination diagrams, the plots formed groups according to habitat (Figure 5b) and season (Figure 5c). Axis1 opposed samples from the town centre (empty circles) located toward the negative pole of the axis to the other samples (Figure 5b). The traps from the town centre were associated with high local road and building covers (variables loROAD and loBUILD, Figure 5a) and with the species *Drosophila melanogaster*, *Drosophila repleta*, *Drosophila busckii* and *Drosophila hydei*. Traps located in the most densely wooded areas (SRTree, SHRUB, LITTER, TREE) and surrounded by fruits (NFRUIT) were associated with *Drosophila suzukii* toward the positive pole of axis 1. Axis 2 separated traps sampled in the summer period with negative values on this axis (Figure 5c) from winter and spring samples with positive values. Most of drosophilidae species were mainly associated with summer samples (*Drosophila phalerata*, *Drosophila kuntzei*, *Drosophila funebris*, *Drosophila immigrans*, Figure 5a), while only a few species (*Drosophila tristis*, *Drosophila subobscura*) responded positively to frost and rain conditions (NFROTS, RAINCUMw), two meteorological characteristics typical of the winter season (see meteorological conditions recorded during the sampling periods, Supp. Mat. G).

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415 *Relationships between plant and Drosophilidae communities*

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In the RDA examining the relationships between plant and Drosophilidae communities (Figure 6), axis1 captured 16.4% of the variance of the data set, while axis2 captured 10.1% of the variance (total for the first two ordering axes: 26.5%; Monte Carlo test: p ≤ 0.05). The

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negative part of axis 1 was characterized by a group of Drosophilidae species (Drosophila busckii, Scaptodrosophila rufifrons, Drosophila funebris, Drosophila immigrans, Drosophila simulans, Figure 6a) associated with relatively open habitats (park and riverside, Figure 6c) characterized by grasses (Lolium perenne, Festuca rubra, F. pratensis), plants indicator of disturbed soil (Polygonum aviculare, Plantago major, growing on bare and trampled soil of paths), ornamental and planted trees (Prunus laurocerasus, Malus sylvestris) and wetland plant species (Salix alba, Populus sp., Agrostis stolonifera, Figure 6b). Isolated at the positive pole of axis 1 (Figure 6a), Drosophila suzukii was associated with open forest habitats colonized by the liana Hedera helix climbing on shrubs and trees (Hed.helS and Hed.helT in Figure 6b) and characterized by a dense shrub layer hosting numerous saplings (Acer pseudoplatanus, Fraxinus excelsior, Prunus avium, Viburnum lantana) and common forest herbs (Geum urbanum, Carex sylvatica). The second ordination axis isolated a large group of Drosophilidae species on its negative part (incl. Drosophila hydei, Drosophila melanogaster, Drosophila subobscura, Drosophila bifasciata, Drosophila tristis, Figure 6a) associated with grassland plant species (Arrhenatherum eliatus, Poa trivialis), some of them showing adaptation to mowing (rosette, stoloniferous and prostrated plants: Taraxacum officinale, Plantago lanceolata, Bellis perennis, Trifolium repens) or to soil disturbances (annual plants: Poa annua, Stellaria media), and with a group of nitrophilous plants (Urtica dioica, Galium aparine, Anthriscus sylvestris, Heracleum spondylium, Figure 6b). The Drosophilidae species grouped toward the positive pole of axis 2 (Hirtodrosophila confusa, H. cameraria, Drosophila phalerata, Drosophila kuntzei, Chymomyza amoena) were associated with closed forest habitats dominated by Acer pseudoplatanus in the tree layer, Crataegus monogyna and Sambucus nigra in the shrub layer and characterized by a herb layer colonized by brambles (Rubus caesius, R. fruticosus) under which a dense carpet of creeping Hedera helix (a shade tolerant species) was spreading.
The Spearman correlations between the abundance of *Drosophila suzukii* and the cover of plant species significantly varied between seasons (Supp. Mat. Ia). *Drosophila suzukii* was strongly and positively correlated with *Acer pseudoplatanus* trees (Ace.pseT) during the major part of the year and with *Acer pseudoplatanus* in shrub and herb layers only during the cold periods from October to March. *Drosophila suzukii* also took refuge in sites with a large canopy of the liana *Hedera helix* climbing on trees and shrubs (Hed.helT, Hed.helS) or spreading on the ground (Hed.helH) during the cold months from November to March and also in summer (Hed.helT and Hed.helS in August). Several other forest herbs forming evergreen tussocks or rosettes (*Carex sylvatica*, *Geum urbanum*) and shrubs with a branchy canopy (*Crataegus monogyna*, *Ribes rubrum*, *Sambucus nigra*, *Ulmus minor*) attracted the fly during the cold season. For some plant species, their cover was significantly correlated with the fly abundance only during their flowering period (vernal geophytes: *Arum maculatum*, *Ranunculus ficaria*) or their fruiting period (*Cornus sanguinea*, *Rubus fruticosus*). The bramble *Rubus caesius* attracted the fly both in the cold seasons and during its fruiting period.

Numerous plant species were negatively correlated with the abundance of *Drosophila suzukii* (Supp. Mat. Ib). *Drosophila suzukii* avoided plant species typical of open habitats such as grassland species (grasses: *Arrhenatherum elatius*, *Dactylis glomerata*, *Festuca rubra*, *Holcus lanatus*, *Lolium perenne*), species indicator of mowing and/or trampling (rosette or stoloniferous species: *Bellis perennis*, *Plantago lanceolata*, *Taraxacum officinale*, *Trifolium repens*), disturbed soils (therophytes: *Capsella bursa-pastoris*, *Cardamine hirsuta*, *Conyza canadensis*, *Lapsana communis*, *Mercurialis annua*, *Poa annua*, *Stellaria media*, *Veronica persica*), nutrient-rich soils (nitrophilous/ruderal species: *Anthriscus sylvestris*, *Artemisia vulgaris*, *Galium aparine*, *Heracleum sphondylium*, *Urtica dioica*) and hygrophilous species (*Agrostis stolonifera*, *Angelica sylvestris*, *Carex acutiformis*, *C. hirta*, *Populus* sp., *Salix* sp.).
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Seasonal variations in Drosophila suzukii morphs and wing size

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The proportions of summer, intermediate and winter morphs of *D. suzukii* showed continuous and gradual variations along the year (Figure 7). Summer morph appeared in May and disappeared after November with a peak in July and August. Winter morph was observed from October to May with a maximum in February. Several centimetres of snow were covering the ground during the sampling week of February and *D. suzukii* was still present in the traps; individuals were even observed walking in patches of sun light on tree trunks and flying around the traps in forest habitat.

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The abundance of summer and dark morphs of *D. suzukii* responded to different environmental variables in GLMs (Supp. Mat. H). The abundance of summer morph individuals increased with shrub cover, species richness in fleshy fruit-bearing plant and high temperature and decreased with local building density. Dark morph (=intermediate + winter morph) was promoted by wood and garden cover in the landscape, local shrub and wood debris cover, frost events and was negatively affected by local building density.

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The Wing Area Indices of female and male *D. suzukii* both increased during the cold season and decreased in summer, showing a bell-shaped curve over the course of the year (Figure 8). The Wing Area Indices of males (mean = 2.587 ± 0.011 mm², n = 1332) were lower compared to that of females (mean = 3.212 ± 0.012 mm², n = 1505). The wing size was also significantly different between morph categories and increased from summer to intermediate and winter morphs (Supp. Mat. J) in females (F = 90.456, p < 0.001, ddl = 2) and males (F = 104.159, p < 0.001, ddl = 2). Very few environmental variables were found to explain these variations in GLMs (Supp. Mat. H). The wing size of both females and males
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decreased with high temperature during the sampling week. Only tree species richness was
positively associated with female wing size. This corroborated the variation patterns of Wing
Area Indices between habitats: the wing size was significantly different between habitat types
(Supp. Mat. K) in females (F = 10.739, p < 0.001, ddl = 3) and males (F = 3.108, p = 0.026,
ddl = 3). Both sexes exhibited lower Wing Area Index in the most urbanized habitat (town
centre) compared to the most densely vegetated habitat (forest).

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Discussion

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The present study sheds light on the role of local and landscape factors shaping the diversity and composition of a Drosophilidae community invaded by *Drosophila suzukii* in urban environment. We found that (i) Drosophilidae species richness and abundance were negatively impacted by urbanization and the degree of habitat anthropization, (ii) two species, including *D. suzukii*, dominated the Drosophilidae community, (iii) Drosophilidae species differed in their response to urbanization and environmental variables, (iv) seasonal variations in meteorological variables were major factors driving community composition and richness, (v) *D. suzukii* moved between habitats and between plant species according to seasons and (vi) *D. suzukii* showed contrasted traits between cold and hot periods.

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Drivers of Drosophilidae species richness and abundance in urban environment

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Insect species richness and abundance are commonly described as the result of an
equilibrium between the effects of local and landscape variables (Shackelford et al. 2013;
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Picchi et al. 2016; Adams et al. 2020), local variables having generally a stronger effect on diversity during overwintering (Sarthou et al. 2014). In this study, we showed that Drosophilidae species richness and abundance abruptly declined along the urbanization gradient, from the most natural habitats to town centre. Thus, these two diversity metrics could be used as valuable indicators of habitat degradation associated with urbanization; and in particular Drosophilidae abundance, which is a measure easy to acquire.

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Behind this urbanization gradient negatively impacting Drosophilidae species richness and abundance, a set of environmental variables were involved both at local and landscape scales. Drosophilidae species richness was negatively affected by the density of building in the very close vicinity of the trap, while it increased with shrub and tree covers. The predominance of impervious surfaces at the expense of vegetated ones reduces the opportunity for arthropods to find trophic resources, reproduction sites and shelters (Fenoglio et al. 2020). The atmospheric pollution associated with urbanization has also been demonstrated to cause significant genetic damage in the organisms of Drosophila (de Santana et al. 2018) and may be another component of the urban hostility for this taxonomic group. Drosophilidae abundance followed the same pattern as species richness, decreasing with local building and road density and increasing with shrub cover. Nevertheless, Drosophilidae abundance was also sensitive to plant species richness in shrub and tree layers. These two vegetation layers harbor several fleshy-fruited host plants (Ribes rubrum, Rubus fruticosus, R. caesius, Sambucus nigra, Prunus sp., etc.) and varied plant families whose diversity increases the diversity of potential feeding and breeding substrates for drosophila, i.e. the diversity of nectars and fruits, two major elements of drosophila diets (Poyet et al. 2015; Tochen et al. 2016). Wood debris also promoted Drosophilidae abundance in our study. Dead trees and decaying branches host many fungus sporophores consumed by drosophila (Kearney 1983; Shorrocks & Charlesworth 1980). Wood debris can also serve as microhabitat as they hide a
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labyrinthic network of holes and galleries commonly used by a wide range of insects
(Sandström et al. 2019).

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At the landscape scale, Drosophilidae abundance decreased with the proportion of building. The dominance of building in the landscape increases the physical isolation of patches of natural habitats in a hostile matrix in accordance with the theory of island biogeography (MacArthur and Wilson 1967) applied to urban terrestrial habitats (Bode & Maciejewski 2014; Fattorini et al. 2018). This mineral urban matrix composed of asphalt and concrete is devoid of food and shelter for most insect species that may impede their movement (Bode and Maciejewski 2014) and limit the connectivity between wooded patches (Beninde et al. 2015). The cover of water body also increased the proportion of hostile abiotic element in the landscape, contributing to the decrease in Drosophilidae abundance and richness in the study. The covers of both buildings/roads and water form abiotic patches in the landscape mosaic, the first being artificial structures made of concrete and the second a natural liquid area. These two landscape features share two common characteristics from an insect perception: they lack from food resources for flies and are even hostile elements due to the lethal risk of drowning for insects in water or being hit by car traffic on road. These two abiotic landscape elements had convergent negative effect on fly populations and diversity in our study.

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*Community composition*

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The Drosophilidae community was largely dominated by two species, the native *D. subobscura* and the invasive pest *D. suzukii*, in the present study. *D. suzukii* was the second dominant Drosophilidae species, whatever the habitat considered (Table 1). Thus, urban areas
and their mosaic of habitat clearly play a role of reservoir of *D. suzukii* and may become a potential source of infestation to nearby agricultural fields. This dominance of *D. subobscura* and *D. suzukii* in the Drosophilidae community is consistent with several other works conducted in France, in vineyards (Delbac et al. 2020) and in large and ancient forest (Poyet et al., 2014). In urbanized areas of Alabama, USA, *D. suzukii* was not noticed a dominant species, being the fifth most abundant Drosophila of the study (Bombin & Reed, 2016). *D. subobscura* was absent in that collection, given this species is exotic in USA. Based to the hierarchical continuum concept (Deconninck et al. 2024), our results show that *D. suzukii* can be considered as a core species structuring the adult Drosophilidae communities. Its dominance can be partly explained by the match between its high polyphagia and the high diversity of suitable fleshy fruits in the region (about half of them are used by the fly; Poyet et al. 2015). *D. suzukii* and *D. subobscura* are generally codominant species in wild fruit of natural habitats (Poyet et al. 2014). On the contrary, in suboptimal or decaying fruit, *D. suzukii* becomes a satellite species with a low effect on fruit fly community at the larval stage (Deconninck et al. 2024). An exotic species integrating a native community may have negative, neutral or positive influences on resident species. A question then arises: how these two dominant species successfully coexist over the course of a year? Niche partitioning in terms of resource requirements and temporal use could help explaining this durable coexistence (Finke and Snyder 2008). The first dominant species *D. subobscura* is known to have no impact on the oviposition activity of *D. suzukii* (i.e. a neutral effect, Ulmer et al. 2021) and the two Drosophila are complementary species in the use of trophic resources (Poyet et al. 2014): *D. suzukii* pierces the skin of ripening fruits hanging on trees, and creates scars on them, enabling pathogens to enter the fruit and make it rot and fall prematurely. This benefits *D. subobscura* females that lay their eggs on rotting fruits fallen on the ground after their infestation by *D. suzukii* (Poyet et al. 2014). This facilitation process through temporal
partitioning of their larval trophic niche may explain the success of their coexistence (Atkinson 1979; Nunney 1990) and their shared dominance in the flying adult community in the aerial compartment of the ecosystem.

In the present study, landscape and local variables had strong effects on Drosophilidae community composition, but different effects on different taxa. This phenomenon of divergent responses of taxa to urbanization have already been reported in other groups of insects (Persson et al. 2020). The large majority of Drosophilidae species preferred urban forest and park habitats in the landscape and thus positively responded to the natural elements at local scale (litter cover, covers of the three vegetation layers, diversity of fruiting plants). Only *Drosophila melanogaster* was more abundant in the town centre, in fruit shops and houses and in other sites dominated by buildings and roads. The preference of *D. melanogaster* for urbanized environments had already been observed by Avondet et al. (2003) who mostly trapped the species in the business district and apartments. *D. melanogaster* is maybe the most commensal *Drosophila* of human; the disappearance of wild behaviour in favour of domestic behaviour in its worldwide population could date back more than 10 millennia (Lachaise and Silvain 2004). Although *D. suzukii* was highly associated with natural features and in particular wooded elements of the landscape, it remained the second most abundant species in the town centre. Given the recent nature of its invasion and association with human productions, habitats, tourism and traffic axes (Cini et al. 2014; Lavrinienko et al. 2017), this invasive species could also be on the way to domestication.

*Meteorological variables*
Meteorological patterns, that determine seasons along the year, were major factors driving variations in Drosophilidae community richness and composition in our study. The number of frost days and the minimum temperature reached during the week of sampling negatively affected the richness of Drosophilidae species trapped; frost days also affecting their abundance. This reduction of activity with decreasing temperature is well known in flying insects (Welti et al. 2022) and particularly in drosophila species whose population fluctuations (Ørsted et al. 2021) and oviposition frequency (Zerulla et al. 2017) are highly sensitive to thermal extremes. Variations in temperature and precipitation also explained the second gradient of Drosophilidae community composition in multivariate analyses. Most species were abundant during the hottest weeks (Drosophila immigrans, D. phalerata, D. kuntzei, Chymomyza amoena, etc.) and only a few species were associated with frost days and weekly precipitations (Drosophila tristis, D. subobscura, D. bifasciata). This seasonal organization of the activity of these two functional groups of Drosophilidae may increase their temporal complementarity in the use of resources and reduce competition (Nunney 1990). Indeed, a higher quantity of fresh food sources or oviposition sites (nectar, sap, fruit) is available in the warmest seasons up to early autumn but this food is to share between a high number of competing *Drosophila* species. The second group of species occurring mainly in winter and mid-seasons, including *D. subobscura* whose larvae are known to be poor competitors (Budnik and Brncic 1983) and feeding from rotting organic matter and mushrooms (Shorrocks and Bingley 1994), may escape pre-imago competition with the major pool of congeneric species. Given the high number of traps (>500) and their random distribution in each habitat each month, it was not possible to get continuous and individual microclimatic data for each trap, which is a limit of the study. These microclimatic data could have helped to better understand the thermal sheltering role of each habitat (Deconninck et al.
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2024; Graae et al. 2012), and the reasons for changes in the distribution of flies between

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habitats over the seasons.

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*Drosophila suzukii* ecological cycle in urban environment

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The description of chronological relationships between *Drosophila suzukii* populations

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and habitats, environmental variables and plant species for a whole year allowed us to

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reconstruct its ecological and seasonal cycle in urban area. A major observation was that *D.*

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*suzukii* was moving from a habitat to another between seasons to find resources for feeding or

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ovipositing and shelters for overwintering or escaping summer heats. In their study, Ulmer et

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al. (2022) showed that fruit infestation rates by *D. suzukii* responded to natural habitat cover

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in a 100 m radius around sampling sites. This corroborates our results indicating a positive

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effect of forest cover on *D. suzukii* abundance (Supp. Mat. H) within the same radius of 100

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m. This 100 m-distance of habitat influence also corresponds to the daily flight capacity of *D.*

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*suzukii*: flies are able to move daily between neighbouring habitats, driven by temperature,

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humidity and the presence of alternative hosts (Tait et al. 2020), limiting their movements to

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distances of less than 100 m (experimental measures from Vacas et al. (2019)). However,

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long-distance dispersal has also been reported (Tait et al. 2018; Vacas et al. (2019) and the

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spatial scale of habitat influence on drosophila species varies between studies and between

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habitat types. For example, Deconninck et al. (2024) showed an influence of building cover

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on Drosophilidae abundance within a radius of 50 m. Thus, 100 m distance/radius scale seems

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to be particularly appropriated for studying the effect of landscape elements on this fly in an

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urban environment.
In spring, *D. suzukii* was associated with a set of flowering plants present in urban forest and park. These spring blossoms may provide a food source for *D. suzukii* (Tochen et al. 2016) in habitats that are generally devoid of fruits at this period of the year (Poyet et al., 2015). Floral nectars are rich in sugars (Nicolson and Thornburg 2007) and contribute to *D. suzukii* survival in laboratory condition (Tochen et al. 2016) and probably in the field (Poyet et al., 2015; Wiman et al., 2016). From early spring to the end of summer, *D. suzukii* frequented riversides. Here, the fly may benefit from the cooling effect of water streams in urban areas (Murakawa et al. 1991) and the higher atmospheric humidity they produce, as the fly is very sensitive to dryness (Eben et al. 2018). Maceda-Veiga et al. (2021) also found a positive correlation between *D. suzukii* populations and the proximity of river streams in the hot season. In the summer period, *D. suzukii* continued to shelter under the canopy of *Acer pseudoplanus* shrubs and trees and the liana *Hedera helix*, probably to protect from heat waves, deleterious for its fertility (Green et al. 2019). Indeed, the understory vegetation of forest habitats of the region is known to reduce extreme hot temperatures of summer compared to forest outside (Graae et al. 2012; Zellweger et al. 2019). This buffering effect of high regional temperatures by forest ecosystems is well documented in France (Gril et al. 2023) and in the Amiens region (Graae et al. 2012). Vegetation structure, dead wood debris and litter creates favorable microclimates in the understory vegetation benefiting many insect species (Scheffers et al. 2014; Kotze et al. 2022). In the summer and the first part of autumn, *D. suzukii* was associated with fruiting plants. Indeed, the peak of host fruit diversity is reached in October in Amiens region (Poyet et al., 2015). From November to March, *D. suzukii* took refuge in forest for overwintering and in particular in sites with a dense cover of brambles, shrubs and dead wood fragments on the ground. The fly was even trapped and observed in activity in this forest habitat in a week of February when the ground was covered by several centimetres of snow and the maximum temperatures recorded in the week did not
exceed 6°C and the minimum temperatures reached -5°C (mean week temperature = 1.3°C).

Active *D. suzukii* were also observed under low temperature condition in the South of France
(Ulmer et al., 2022) suggesting that its low thermal thresholds are probably overestimated.

This resistance to very low temperatures could suggest an adaptation of populations;
nevertheless, flies are already known to be able to recover from chill coma after 24h exposure
to -1°C (Wallingford et al. 2016). Beyond this chronological organisation of *D. suzukii* along
seasons, urbanization (through local density of road and building) remained the major factor
negatively affecting the abundance of *D. suzukii* while the cover of wooded habitat was the
main landscape-scale variable promoting its populations. These results corroborates those of
other studies (Santoiemma et al. 2018; Ulmer et al. 2022). As for many other insect species,
these isolated wooded elements probably act as stepping stone islands (Be et al. 2017) aiding
the spread and persistence of the fly through the landscape.

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699 *Seasonal polyphenism of spotted-wing Drosophila*

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701 Wing size and body pigmentation in insects are two traits commonly used to assess
702 their fitness and explain their adaptation to varying environmental conditions (Crill et al.
703 1996; Gilchrist and Huey 2004). Because of the correlation between life trait variables, wing
704 size is often used as a proxy of body size and even sometimes body weight (Cavicchi et al.
705 1985; Abbott et al. 2010). In the present study, wing size of *D. suzukii* was higher during cold
706 periods. This result is congruent with the ecological generalizations of the rules of Bergmann
707 and Rensch (Bergmann 1847; Rensch 1938) applied at the intra-specific level (Meiri, 2011).
708 Differences in size are mediated by differences in development times, with the larger body
709 developing for a proportionately longer time. In arthropods, and particularly among
Drosophila species, development time increases with lower temperature (Schlesener et al. 2020), explaining the negative correlation between temperature and body size (Jalal et al. 2015) and why larger individuals are found at higher latitudes, elevations or in colder climates, or even, as it is our case here, in the colder seasons. In our study, *D. suzukii* larvae developing in fruits in October or November and producing imago emerging a few weeks before winter, experienced lower temperature than summer larvae. Traits variation are generally related to variation in functionality, and thus wing plasticity may possibility have an adaptive value. In the study of Fraimout et al. (2018), developmental temperature was found to affect wing morphology and consequently flight performances (speed and acceleration) in *D. suzukii*, the fastest flies being found at the lowest temperature. Winter flies should be able to move rapidly from a site to another, should avoid spending too long time flying under cold conditions and finally should spare energy. In the present study, wing size of *D. suzukii* was larger in female individuals than in male individuals. The size difference observed between male and female is consistent with the sexual dimorphism usually reported in Diptera (Reis et al. 2021) and also known in *D. suzukii* (Tran et al. 2020). This could be explained by a fundamental difference in the way males and females manage their energy budget. Wing size may be the result of selection toward sex-specific fitness optima (Sztepanacz and Houle 2021). In contrast, for one sex, several studies suggest that natural variation in wing size is caused by a combination of genetic and environmental factors. Indeed, an increase of wing size with lower temperatures has been observed on vinegar flies of both sexes (Hoffmann et al. 2003; Fraimout et al. 2018; Koch et al. 2020; Jardeleza et al. 2022). It has been suggested that this increase in wing size observed in *D. suzukii* winter morphs, in winter conditions, could be related to scarcer resources (mate, food) involving longer flight times (Jardeleza et al. 2022). Wing shape has also been shown to vary in *D. suzukii* depending on the species of its host plant during larval development, as demonstrated by Pajač Živković et al. (2018) who
observed narrower wings in flies grown in strawberries and wider wings in for flies grown in grapes. The different types of fruits available in the different seasons could therefore have also influenced the wing size of *D. suzukii* morphs. The same environmental factors (fruiting plant composition and temperature variations) could also explain the differences in wing size between habitats in relation with the urbanization gradient (Mat. Suppl. E). Indeed, wooded habitat are a major source of fruit suitable for the development of *D. suzukii* (Poyet et al. 2015) while, at the opposite, urban environment conditions are well-known to negatively affect the fitness of insect species (Fenoglio et al. 2021).

Darker cuticle pigmentation has been hypothesized to be involved in thermoregulation of ectotherms in cold environments, resulting in increased ultraviolet absorption and increased ability to warm up (Trullas et al. 2007). Shearer et al., (2016) showed that laboratory-simulated winter-like photoperiod and temperature conditions induced higher levels of melanization and larger wing size in *D. suzukii* and that these physiological characters were associated with an increase in cold-tolerance. As we found that wood areas represented possible refuges for *D. suzukii* in the winter, one could also hypothesize that darker winter morphs may benefit the flies in terms of camouflage in areas dominated by dead wood and decomposing leaves.

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753 Toward the use of ecological indicators to manage *D. suzukii* populations

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Knowing where and when *D. suzukii* is present in different habitats is essential for designing management strategies of the pest. In the field, several easy-to-measure variables related to ecosystem composition (identity and abundance of plant species), structure (cover of vegetation layers) or functioning (litter, dead wood debris) can be used as ecological

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indicator of the presence of the fly. Microclimatic dataloggers placed both on the ground and in the tree canopy of urban forests and parks could also contribute our understanding of the small-scale spatial dynamics of *D. suzukii* populations in the vertical structure of the vegetation (Deconninck et al. 2024). Once the risk is evaluated in the field, a subsequent step in the strategy of *D. suzukii* control could consist, for example, in managing the expansion of over-dominant plants sheltering or feeding the fly at the appropriate moment of the year or favouring the presence of predators in microhabitats used by the fly (Ulmer et al. 2021).

Among the wide set of plant species recorded in the study, the liana *Hedera helix* (ivy) was one of the most strongly associated with *D. suzukii*. The fly sheltered in sites with dense canopy of *H. helix* during periods of the most extreme temperatures in both winter and summer. *H. helix* is also known to produce a large amount of nectar in autumn (Timberlake et al. 2021) that can help *D. suzukii* to prepare to the cold season (Poyet et al., 2015). Moreover, Grassi et al. (2018) also found that ivy berries can serve as an alternative but suboptimal non-crop host during the late dormant period for the fly. Thus, this plant may contribute to fulfil three major vital functions for the fly by providing shelter, food and breeding substrate. *H. helix* is considered as one of the most aggressive native plant species that may impact the plant richness of native woodlands by becoming ‘over-dominant’ (Marrs et al. 2013). Its abundance significantly increased in European forests over the last 50 years, as a consequence of temperature increase and a reduction in severe frost events accompanying climate change (Heinrichs and Schmidt 2015; Perring et al. 2020). As a consequence, this liana is likely to become more and more influential on the persistence of *D. suzukii* through time with climate change. A better management of *H. helix* expansion (often neglected) appears to be primordial in urban areas, in particular to reduce the number of overwintering microsites available to *D. suzukii*. Other plants attracted the fly during overwintering and hot periods and played a similar role as ivy did. It is the case of brambles (*Rubus* sp.) and young saplings and shrubs of
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*Acer pseudoplatanus*. In general, a dense shrub layer, whatever its species composition, is a good indicator of the presence of *D. suzukii*.

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Plant communities containing fleshy-fruited plants providing food and oviposition sites to *D. suzukii* in summer and early autumn are also key elements in the persistence of the fly in urban areas. Nevertheless, the fruits of these plants also feed a diversified community of birds (Pesotskaya et al. 2020) and mammals (Godó et al. 2022), and their elimination would threaten the biodiversity in invertebrates and is not recommended. One solution that could divert the pest away from infesting the fruits of wild plants would be to use a dead-end trap plant (Ulmer et al. 2020). These trap plants, attractive to *D. suzukii* gravid females searching oviposition sites while being lethal for its offspring, could be integrated in hedgerows of urban gardens and parks susceptible to *D. suzukii* invasion.

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Abiotic elements of the ecosystem such as litter and dead wood debris are also ecological indicators strongly associated with the presence of *D. suzukii*. This decaying plant matter is a major component of ecosystem functioning and contributes to overall diversity by supporting fungi and insects that feed on it and/or live in it (Jabin et al. 2004). We suggest to maintain these dead wood debris to promote the diversity of local predators and competitors of *D. suzukii* in these sites as recommended by Ulmer et al. (2021). Nevertheless, nest boxes for insectivorous birds and bats, known to consume *D. suzukii* (Dekeukeleire et al. 2020), could also be installed in risk areas to prevent outbreak of the pest (Garfinkel and Johnson 2015).
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**Funding**

Romain Ulmer was supported by a doctoral fellowship from the French Ministry of Higher Education, Research and Innovation.

**Competing Interests**

The authors have no relevant financial or non-financial interests to disclose.

**Author Contributions**

Romain Ulmer, Aude Couty, Patrice Eslin and Olivier Chabrerie contributed to the study conception and design. Material preparation, data collection and analysis were performed by all authors. The first draft of the manuscript was written by Romain Ulmer, Aude Couty, Patrice Eslin and Olivier Chabrerie and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
TABLES

<table><caption>**Table 1** Abundance of Drosophilidae species in the study. N ind: total number of individuals trapped, Max: maximum number of individuals per trap, Min: minimum number of individuals per trap, Mean: mean number of individuals per trap, SE: standard error, %: percentage of individuals trapped.</caption><thead><tr><th rowspan="2">Species</th><th rowspan="2">Code</th><th colspan="6">Total study (526 traps)</th></tr><tr><th>N ind</th><th>Min</th><th>Max</th><th>Mean</th><th>SE</th><th>%</th></tr></thead><tbody><tr><td>Chymomyza amoena</td><td>Chy.amo</td><td>4</td><td>0</td><td>2</td><td>0.008</td><td>0.005</td><td>0.004</td></tr><tr><td>Drosophila bifasciata</td><td>Dro.bif</td><td>123</td><td>0</td><td>15</td><td>0.234</td><td>0.061</td><td>0.135</td></tr><tr><td>Drosophila busckii</td><td>Dro.bus</td><td>325</td><td>0</td><td>21</td><td>0.618</td><td>0.095</td><td>0.356</td></tr><tr><td>Drosophila funebris</td><td>Dro.fun</td><td>128</td><td>0</td><td>7</td><td>0.243</td><td>0.039</td><td>0.140</td></tr><tr><td>Drosophila helvetica</td><td>Dro.hel</td><td>1</td><td>0</td><td>1</td><td>0.002</td><td>0.002</td><td>0.001</td></tr><tr><td>Drosophila hydei</td><td>Dro.hyd</td><td>720</td><td>0</td><td>45</td><td>1.369</td><td>0.162</td><td>0.788</td></tr><tr><td>Drosophila immigrans</td><td>Dro.imm</td><td>5083</td><td>0</td><td>627</td><td>9.663</td><td>1.791</td><td>5.561</td></tr><tr><td>Drosophila kuntzei</td><td>Dro.kun</td><td>4496</td><td>0</td><td>910</td><td>8.548</td><td>2.700</td><td>4.919</td></tr><tr><td>Drosophila melanogaster</td><td>Dro.mel</td><td>1325</td><td>0</td><td>96</td><td>2.519</td><td>0.352</td><td>1.450</td></tr><tr><td>Drosophila obscura</td><td>Dro obs</td><td>1</td><td>0</td><td>1</td><td>0.002</td><td>0.002</td><td>0.001</td></tr><tr><td>Drosophila phalerata</td><td>Dro.pha</td><td>1794</td><td>0</td><td>327</td><td>3.411</td><td>0.848</td><td>1.963</td></tr><tr><td>Drosophila repleta</td><td>Dro.rep</td><td>67</td><td>0</td><td>6</td><td>0.127</td><td>0.025</td><td>0.073</td></tr><tr><td>Drosophila simulans</td><td>Dro.sim</td><td>94</td><td>0</td><td>9</td><td>0.179</td><td>0.038</td><td>0.103</td></tr><tr><td>Drosophila subobscura</td><td>Dro.sub</td><td>41433</td><td>0</td><td>2422</td><td>78.770</td><td>7.965</td><td>45.333</td></tr><tr><td>Drosophila suzukii</td><td>Dro.suz</td><td>35053</td><td>0</td><td>1565</td><td>66.641</td><td>7.114</td><td>38.352</td></tr><tr><td>Drosophila testacea</td><td>Dro.tes</td><td>1</td><td>0</td><td>1</td><td>0.002</td><td>0.002</td><td>0.001</td></tr><tr><td>Drosophila transversa</td><td>Dro.tra</td><td>7</td><td>0</td><td>4</td><td>0.013</td><td>0.008</td><td>0.008</td></tr><tr><td>Drosophila tristis</td><td>Dro.tri</td><td>551</td><td>0</td><td>28</td><td>1.048</td><td>0.133</td><td>0.603</td></tr><tr><td>Gitona distigma</td><td>Git.dis</td><td>8</td><td>0</td><td>2</td><td>0.015</td><td>0.006</td><td>0.009</td></tr><tr><td>Hirtodrosophila cameraria</td><td>Hir.cam</td><td>7</td><td>0</td><td>2</td><td>0.013</td><td>0.006</td><td>0.008</td></tr><tr><td>Hirtodrosophila confusa</td><td>Hir.con</td><td>27</td><td>0</td><td>3</td><td>0.051</td><td>0.014</td><td>0.030</td></tr><tr><td>Leucophenga maculata</td><td>Leu.mac</td><td>8</td><td>0</td><td>2</td><td>0.015</td><td>0.006</td><td>0.009</td></tr><tr><td>Phortica semivirgo</td><td>Phosem</td><td>2</td><td>0</td><td>1</td><td>0.004</td><td>0.003</td><td>0.002</td></tr><tr><td>Phortica variegata</td><td>Pho.var</td><td>9</td><td>0</td><td>2</td><td>0.017</td><td>0.006</td><td>0.010</td></tr><tr><td>Scaptodrosophila rufifrons</td><td>Sca.ruf</td><td>130</td><td>0</td><td>13</td><td>0.247</td><td>0.045</td><td>0.142</td></tr></tbody><tfoot><tr><td>Total</td><td></td><td>91397</td><td></td><td></td><td></td><td></td><td></td></tr></tfoot></table>
FIGURES

**Fig. 1** Proportion of land covers around sampling traps (radius = 100 m) located in the four urban habitats studied in Amiens city: urban forest (FOREST), park (PARK), riverside (RIVER) and town centre (TOWN). Legend of land covers: BUILD: building, SOIL: bare soil, ROAD: road and car park, PATH: path, HSTRIP: herbaceous strip, WATER: water, HEDGE: hedgerow, GARDEN: private garden, CROP: crop (cereals), GRASS: grassland, WOOD: wooded area

**Fig. 2** Relative abundance of the 14 most abundant Drosophilidae species in the four urban habitats of Amiens city. Numeric values of total number of individuals trapped, maximum, minimum, mean number of individuals per trap and per habitat are given in Suppl. Mat X.

**Fig. 3** Seasonal distribution of *Drosophila suzukii* individuals among the different urban habitats (X-axis: months from September 2018 to August 2019; Y-axis: relative abundance of individuals between habitats for each month)

**Fig. 4** Mean Drosophilidae species richness (a) and abundance (b) per trap (±SE) in the four urban habitats sampled. Forest: n= 135, park: n = 134, riverside: n = 128, town centre: n = 129. Significant differences were found in Drosophilidae species richness (F = 72.496; p < 0.001 between pairs of habitat) and abundance (F = 39.062; p < 0.001) between habitats

**Fig. 5** Redundancy analysis (RDA) coupling environment and Drosophilidae species matrices. (a) Diagram of Drosophilidae species (lowercase letters) and environmental variables (capital letters), (b) Diagram of plots grouped by habitats and (c) grouped by seasons. Only the most significant environmental variables are shown (cutoff r² value = 0.1)
**Fig. 6** Redundancy analysis (RDA) coupling plant and Drosophilidae species matrices. (a) Diagram of Drosophilidae species, (b) Diagram of plant species. Only the most significant environmental variables are shown (cutoff r² value = 0.1)

**Fig. 7** Proportions of *Drosophila suzukii* morphs over the course of the year

**Fig. 8** Mean wing sizes (± SE; wing area index in mm²) variation of female and male *Drosophila suzukii* over the course of the year. The number of traps used for wing trait measurements and the percentage of dark morph (D=intermediate + winter morphs) among measured individuals are indicated next to the corresponding dots on the graph. In each trap, between one and 5 individuals (depending on their availability in traps and conservation state) were measured for each sex. Total measured individuals: 1505 females in 377 traps and 1332 males in 322 traps
**Fig. 1** Proportion of land covers around sampling traps (radius = 100 m) located in the four urban habitats studied in Amiens city: urban forest (FOREST), park (PARK), riverside (RIVER) and town centre (TOWN). Legend of land covers: BUILD: building, SOIL: bare soil, ROAD: road and car park, PATH: path, HSTRIP: herbaceous strip, WATER: water, HEDGE: hedgerow, GARDEN: private garden, CROP: crop (cereals), GRASS: grassland, WOOD: wooded area

<figure><img src="image_3.png" /></figure>
**Fig. 2** Relative abundance of the 14 most abundant Drosophilidae species in the four urban habitats of Amiens city. Numeric values of total number of individuals trapped, maximum, minimum, mean number of individuals per trap and per habitat are given in Suppl. Mat D.

<figure><img src="image_4.png" /></figure>
**Fig. 3** Seasonal distribution of *Drosophila suzukii* individuals among the different urban habitats (X-axis: months from September 2018 to August 2019; Y-axis: relative abundance of individuals between habitats for each month).

<figure><img src="image_5.png" /></figure>
**Fig. 4** Mean Drosophilidae species richness (a) and abundance (b) per trap (±SE) in the four urban habitats sampled. Forest: n= 135, park: n = 134, riverside: n = 128, town centre: n = 129. Significant differences were found in Drosophilidae species richness (F = 72.496; p < 0.001 between pairs of habitat) and abundance (F = 39.062; p < 0.001) between habitats

<figure><img src="image_6.png" /><figcaption>(b)</figcaption></figure>

<figure><img src="image_7.png" /></figure>
<caption>**Fig. 5** Redundancy analysis (RDA) coupling environment and Drosophilidae species matrices. (a) Diagram of Drosophilidae species (lowercase letters) and environmental variables (capital letters), (b) Diagram of plots grouped by habitats and (c) grouped by seasons. Only the most significant environmental variables are shown (cutoff r² value = 0.1). Codes and full names for Drosophilidae species are given in Table 1</caption>

<figure><img src="image_8.png" /><figcaption>(a)</figcaption></figure>
(b)

<figure><img src="image_9.png" /></figure>
(c)

<figure><img src="image_10.png" /></figure>
<caption>**Fig. 6** Redundancy analysis (RDA) coupling plant and Drosophilidae species matrices. (a) Diagram of Drosophilidae species, (b) Diagram of plant species. Only the most significant environmental variables are shown (cutoff r² value = 0.1). Codes and full names for Drosophilidae species are given in Table 1</caption>

(a)

<figure><img src="image_11.png" /></figure>
<figure><img src="image_12.png" /><figcaption>(b)</figcaption></figure>
<figure><img src="image_13.png" /><figcaption>**Fig. 7** Proportions of *Drosophila suzukii* morphs over the course of the year</figcaption></figure>
**Fig. 8** Mean wing sizes (± SE; wing area index in mm²) variation of female and male *Drosophila suzukii* over the course of the year. The number of traps used for wing trait measurements and the percentage of dark morph (D=intermediate + winter morphs) among measured individuals are indicated next to the corresponding dots on the graph. In each trap, between one and 5 individuals (depending on their availability in traps and conservation state) were measured for each sex. Total measured individuals: 1505 females in 377 traps and 1332 males in 322 traps

<figure><img src="image_14.png" /></figure>
SUPPLEMENTARY INFORMATION

**Supp. Mat. A:** Distribution of Drosophilidae species in the fruit stores and houses of Amiens
city. N ind: total number of individuals trapped, Max: maximum number of individuals per
trap, Min: minimum number of individuals per trap, Mean: mean number of individuals per
trap, SE: standard error, Frequency: number of traps with presence of the species / total
number of traps, %: percentage of individuals trapped.

**Supp. Mat. B:** Picture of male individuals showing the 3 morphs considered in the analysis.
(a) summer morph, (b) intermediate morph and (c) winter morph.

**Supp. Mat. C:** List of the variables used in the study.

**Suppl. Mat. D** Distribution of Drosophilidae species in the four urban habitats of Amiens
city. N ind: total number of individuals trapped, Max: maximum number of individuals per
trap, Min: minimum number of individuals per trap, Mean: mean number of individuals per
trap, SE: standard error, %: percentage of individuals trapped.

**Suppl. Mat. E** Seasonal distribution of the proportion of individuals of the most abundant
*Drosophilidae* species among the different urban habitats (X-axes: months from September
2018 to August 2019; Y-axes: relative abundance of individuals in percentage between
habitats for each month).

**Suppl. Mat. F** Variation of the number of individuals of the most abundant Drosophilidae
species in the different urban habitats over the course of the year (X-axes: months from
September 2018 to August 2019; Y-axes: cumulated number of individuals in the four
habitats for each month).
**Supp. Mat. G:** meteorological characteristics of the sampling periods. Cumulative temperature (red line): sum of daily mean temperatures (>0°C) of the sampling week (degree-days). Cumulative precipitation (blue histograms): total rainfall for the week of sampling (mm).

**Supp. Mat. H** Effect of environmental variables on the species richness of Drosophilidae community, the number of Drosophilidae individuals (Drosophila abundance), the number of *D. suzukii* individuals (*D. suzukii* abundance), the number of summer and dark morphs of *D. suzukii* and the wing area index (wing size) of female and male *D. suzukii* per trap analysed by GLM. n = number of traps used in analyses.

**Supp. Mat. I** Plant species the most correlated with the abundance of *Drosophila suzukii* over the year (Spearman correlation coefficients, non-significant results are not shown, *: p<0.05, **: p<0.01, ***: p<0.001). Only species present in at least 2% of the sampling plots were selected and samples from town centre were removed. Layer (vegetation layer): T: tree layer, S: shrub layer, H: herb layer.

**Supp. Mat. J:** Differences in wing sizes (± SE, wing area index in mm²) between morph categories (summer, intermediate and winter morphs) of *Drosophila suzukii* females (a) and males (b). The number of individuals used for wing trait measurements is indicated in italic above the histograms. The wing size was significantly different between morph categories in females (F = 90.456, p < 0.001, ddl = 2) and males (F = 104.159, p < 0.001, ddl = 2).

**Supp. Mat. K:** Differences in wing sizes (wing area index in mm², mean ± SE) between urban habitats (forest, park, riverside, town centre) of *Drosophila suzukii* females (a) and males (b). The number of fly individuals used for wing size measurements is indicated in italic above histograms. The wing size was significantly different between habitats in females
(F = 10.739, p < 0.001, ddl = 3) and males (F = 3.108, p = 0.026, ddl = 3). Letters above histograms indicate significative differences between habitats.
**Supp. Mat. A:** Distribution of Drosophilidae species in the fruit stores and houses of Amiens
city (north of France). N ind: total number of individuals trapped, Max: maximum number of
individuals per trap, Min: minimum number of individuals per trap, Mean: mean number of
individuals per trap, SE: standard error, Frequency: number of traps with presence of the
species / total number of traps, %: percentage of individuals trapped.

<table><thead><tr><th rowspan="2">Species</th><th rowspan="2">Code</th><th colspan="8">Fruit stores and houses (139 traps)</th></tr><tr><th>N ind</th><th>Min</th><th>Max</th><th>Mean</th><th>SE</th><th>Frequency</th><th>%</th></tr></thead><tbody><tr><td>Chymomyza amoena</td><td>Chy.amo</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila bifasciata</td><td>Dro.bif</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila busckii</td><td>Dro.bus</td><td>33</td><td>0</td><td>16</td><td>0.237</td><td>0.123</td><td>0.079</td><td>2.25</td></tr><tr><td>Drosophila funebris</td><td>Dro.fun</td><td>8</td><td>0</td><td>2</td><td>0.058</td><td>0.027</td><td>0.036</td><td>0.55</td></tr><tr><td>Drosophila helvetica</td><td>Dro.hel</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila hydei</td><td>Dro.hyd</td><td>274</td><td>0</td><td>77</td><td>1.971</td><td>0.737</td><td>0.223</td><td>18.68</td></tr><tr><td>Drosophila immigrans</td><td>Dro.imm</td><td>40</td><td>0</td><td>6</td><td>0.288</td><td>0.078</td><td>0.129</td><td>2.73</td></tr><tr><td>Drosophila kuntzei</td><td>Dro.kun</td><td>4</td><td>0</td><td>2</td><td>0.029</td><td>0.020</td><td>0.014</td><td>0.27</td></tr><tr><td>Drosophila melanogaster</td><td>Dro.mel</td><td>995</td><td>0</td><td>171</td><td>7.158</td><td>2.009</td><td>0.360</td><td>67.83</td></tr><tr><td>Drosophila obscura</td><td>Droobs</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila phalerata</td><td>Dro.pha</td><td>4</td><td>0</td><td>2</td><td>0.029</td><td>0.018</td><td>0.022</td><td>0.27</td></tr><tr><td>Drosophila repleta</td><td>Dro.rep</td><td>32</td><td>0</td><td>7</td><td>0.230</td><td>0.082</td><td>0.086</td><td>2.18</td></tr><tr><td>Drosophila simulans</td><td>Dro.sim</td><td>7</td><td>0</td><td>4</td><td>0.050</td><td>0.036</td><td>0.014</td><td>0.48</td></tr><tr><td>Drosophila subobscura</td><td>Dro.sub</td><td>45</td><td>0</td><td>19</td><td>0.324</td><td>0.151</td><td>0.108</td><td>3.07</td></tr><tr><td><strong>Drosophila suzukii</strong></td><td><strong>Dro.suz</strong></td><td><strong>24</strong></td><td><strong>0</strong></td><td><strong>11</strong></td><td><strong>0.173</strong></td><td><strong>0.093</strong></td><td><strong>0.050</strong></td><td><strong>1.64</strong></td></tr><tr><td>Drosophila testacea</td><td>Dro.tes</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila transversa</td><td>Dro.tra</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila tristis</td><td>Dro.tri</td><td>1</td><td>0</td><td>1</td><td>0.007</td><td>0.007</td><td>0.007</td><td>0.07</td></tr><tr><td>Gitona distigma</td><td>Git.dis</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Hirtodrosophila cameraria</td><td>Hir.cam</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Hirtodrosophila confusa</td><td>Hir.con</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Leucophenga maculata</td><td>Leu.mac</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Phortica semivirgo</td><td>Pho.sem</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Phortica variegata</td><td>Pho.var</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Scaptodrosophila rufifrons</td><td>Sca.ruf</td><td>0</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.00</td></tr></tbody><tfoot><tr><td>Total</td><td></td><td>1467</td><td></td><td></td><td></td><td></td><td></td><td>100.000</td></tr></tfoot></table>
**Supp. Mat. B:** Picture of male individuals showing the 3 morphs considered in the analysis.

(a) summer morph, (b) intermediate morph and (c) winter morph.

<figure><img src="image_15.png" /></figure>
<table><caption>Supp. Mat. C: List of the variables used in the study.</caption><thead><tr><th>Category</th><th>Variable description</th><th>Unit</th><th>Code</th></tr></thead><tbody><tr><td rowspan="10">Insects (in traps)</td><td>Abundance of Drosophila suzukii</td><td>individuals</td><td>DSabund</td></tr><tr><td>Species richness of Drosophilidae</td><td>species</td><td>SRdroso</td></tr><tr><td>Abundance of Drosophilidae</td><td>individuals</td><td>ABUNdroso</td></tr><tr><td>Abundance of D. suzukii male</td><td>individuals</td><td>Dsmale</td></tr><tr><td>Abundance of D. suzukii female</td><td>individuals</td><td>Dsfemale</td></tr><tr><td>Abundance of D. suzukii summer morph</td><td>individuals</td><td>DSEstivale</td></tr><tr><td>Abundance of D. suzukii intermediate morph</td><td>individuals</td><td>DSIntermed</td></tr><tr><td>Abundance of D. suzukii winter morph</td><td>individuals</td><td>DSHiver</td></tr><tr><td>Abundance of D. suzukii dark morph (intermediate + winter)</td><td>individuals</td><td>DSInt_Hiver</td></tr><tr><td>Abundance of other non-drosophilidae arthropods</td><td>individuals</td><td>ABUNarth</td></tr><tr><td rowspan="2">Life traits of D. suzukii</td><td>Average wing surface area of D. suzukii female</td><td>mm²</td><td>WINGfem</td></tr><tr><td>Average wing surface area of D. suzukii male</td><td>mm²</td><td>WINGmal</td></tr><tr><td rowspan="10">Local environment (5m-radius around traps)</td><td>Cover of tree layer (height&gt;8m)</td><td>%</td><td>TREE</td></tr><tr><td>Plant species richness in tree layer</td><td>species</td><td>SRtree</td></tr><tr><td>Cover of shrub layer (height between 1m and 8m)</td><td>%</td><td>SHRUB</td></tr><tr><td>Plant species richness in shrub layer</td><td>species</td><td>SRshrub</td></tr><tr><td>Cover of herb layer (height&lt;1m)</td><td>%</td><td>HERB</td></tr><tr><td>Plant species richness in herb layer</td><td>species</td><td>SRherb</td></tr><tr><td>Cover of dead wood debris</td><td>%</td><td>DWOOD</td></tr><tr><td>Cover of leaf litter</td><td>%</td><td>LITTER</td></tr><tr><td>Cover of waste</td><td>%</td><td>WASTE</td></tr><tr><td>Cover of river</td><td>%</td><td>IoRIVER</td></tr><tr><td>Cover of road</td><td>%</td><td>IoROAD</td></tr><tr><td>Cover of building</td><td>%</td><td>IoBUILD</td></tr><tr><td>Cover of trail</td><td>%</td><td>IoPATH</td></tr><tr><td>Number of fruiting plant species around the trap (radius = 10m)</td><td>species</td><td>NFRUIT</td></tr><tr><td rowspan="10">Landscape (100m-radius around traps)</td><td>Cover of herbaceous strip</td><td>%</td><td>HSTRIP</td></tr><tr><td>Cover of building</td><td>%</td><td>BUILD</td></tr><tr><td>Cover of forest</td><td>%</td><td>WOOD</td></tr><tr><td>Cover of crop</td><td>%</td><td>CROP</td></tr><tr><td>Cover of trail</td><td>%</td><td>PATH</td></tr><tr><td>Cover of water</td><td>%</td><td>WATER</td></tr><tr><td>Cover of hedgerow</td><td>%</td><td>HEDGE</td></tr><tr><td>Cover of private garden</td><td>%</td><td>GARDEN</td></tr><tr><td>Cover of grassland</td><td>%</td><td>GRASS</td></tr><tr><td>Cover of bare soil</td><td>%</td><td>SOIL</td></tr><tr><td>Cover of road and paved surface</td><td>%</td><td>ROAD</td></tr><tr><td rowspan="7">Meteorology of the year (between the 1st January and the day of trap collection)</td><td>Cumulative temperatures &gt;= 0, degree-days (year)</td><td>°C</td><td>TEMPCUMy</td></tr><tr><td>Cumulative precipitation (year)</td><td>mm</td><td>RAINCUMy</td></tr><tr><td>Mean of maximum temperatures (year)</td><td>°C</td><td>TEMPMAXy</td></tr><tr><td>Mean of minimum temperatures (year)</td><td>°C</td><td>TEMPMINy</td></tr><tr><td>Mean of mean temperatures (year)</td><td>°C</td><td>TEMPMEAy</td></tr><tr><td>Highest temperature (year)</td><td>°C</td><td>TEMPTOPy</td></tr><tr><td>Lowest temperature (year)</td><td>°C</td><td>TEMPLOWy</td></tr><tr><td>Number of frost days (year)</td><td>/</td><td>NFROSTy</td></tr><tr><td rowspan="7">Meteorology of the sampling week</td><td>Cumulative temperatures &gt;= 0, degree-days (week)</td><td>°C</td><td>TEMPCUMw</td></tr><tr><td>Cumulative precipitation (week)</td><td>mm</td><td>RAINCUMw</td></tr><tr><td>Mean of maximum temperatures (week)</td><td>°C</td><td>TEMPMAXw</td></tr><tr><td>Mean of minimum temperatures (week)</td><td>°C</td><td>TEMPMINw</td></tr><tr><td>Mean of mean temperatures (week)</td><td>°C</td><td>TEMPMEAw</td></tr><tr><td>Highest temperature (week)</td><td>°C</td><td>TEMPTOPw</td></tr><tr><td>Lowest temperature (week)</td><td>°C</td><td>TEMPLOWw</td></tr><tr><td>Number of frost days (week)</td><td>/</td><td>NFROSTw</td></tr></tbody></table>
**Suppl. Mat. D** Distribution of Drosophilidae species in the four urban habitats of Amiens
city. N ind: total number of individuals trapped, Max: maximum number of individuals per
trap, Min: minimum number of individuals per trap, Mean: mean number of individuals per
trap, SE: standard error, %: percentage of individuals trapped.

<table><thead><tr><th rowspan="2">Species</th><th rowspan="2">Code</th><th colspan="5">FOREST (135 traps)</th><th colspan="5">PARK (134 traps)</th></tr><tr><th>N ind</th><th>Max</th><th>Mean</th><th>SE</th><th>%</th><th>N ind</th><th>Max</th><th>Mean</th><th>SE</th><th>%</th></tr></thead><tbody><tr><td>Chymomyza amoena</td><td>Chy.amo</td><td>3</td><td>2</td><td>0.022</td><td>0.017</td><td>0.01</td><td>1</td><td>1</td><td>0.007</td><td>0.007</td><td>0.00</td></tr><tr><td>Drosophila bifasciata</td><td>Dro.bif</td><td>72</td><td>13</td><td>0.533</td><td>0.179</td><td>0.15</td><td>39</td><td>15</td><td>0.291</td><td>0.142</td><td>0.15</td></tr><tr><td>Drosophila busckii</td><td>Dro.bus</td><td>100</td><td>11</td><td>0.741</td><td>0.177</td><td>0.21</td><td>58</td><td>12</td><td>0.433</td><td>0.128</td><td>0.22</td></tr><tr><td>Drosophila funebris</td><td>Dro.fun</td><td>54</td><td>6</td><td>0.400</td><td>0.092</td><td>0.11</td><td>22</td><td>5</td><td>0.164</td><td>0.058</td><td>0.08</td></tr><tr><td>Drosophila helvetica</td><td>Dro.hel</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>1</td><td>1</td><td>0.007</td><td>0.007</td><td>0.00</td></tr><tr><td>Drosophila hydei</td><td>Dro.hyd</td><td>162</td><td>45</td><td>1.200</td><td>0.355</td><td>0.34</td><td>329</td><td>28</td><td>2.455</td><td>0.451</td><td>1.23</td></tr><tr><td>Drosophila immigrans</td><td>Dro.imm</td><td>3326</td><td>627</td><td>24.637</td><td>6.592</td><td>6.90</td><td>859</td><td>77</td><td>6.410</td><td>1.092</td><td>3.21</td></tr><tr><td>Drosophila kuntzei</td><td>Dro.kun</td><td>4248</td><td>910</td><td>31.467</td><td>10.286</td><td>8.81</td><td>88</td><td>26</td><td>0.657</td><td>0.244</td><td>0.33</td></tr><tr><td>Drosophila melanogaster</td><td>Dro.mel</td><td>168</td><td>17</td><td>1.244</td><td>0.251</td><td>0.35</td><td>180</td><td>14</td><td>1.343</td><td>0.217</td><td>0.67</td></tr><tr><td>Drosophila obscura</td><td>Dro obs</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>1</td><td>1</td><td>0.007</td><td>0.007</td><td>0.00</td></tr><tr><td>Drosophila phalerata</td><td>Dro.pha</td><td>1393</td><td>327</td><td>10.319</td><td>3.177</td><td>2.89</td><td>288</td><td>45</td><td>2.149</td><td>0.565</td><td>1.07</td></tr><tr><td>Drosophila repleta</td><td>Dro.rep</td><td>2</td><td>1</td><td>0.015</td><td>0.010</td><td>0.00</td><td>7</td><td>3</td><td>0.052</td><td>0.027</td><td>0.03</td></tr><tr><td>Drosophila simulans</td><td>Dro.sim</td><td>58</td><td>9</td><td>0.430</td><td>0.121</td><td>0.12</td><td>18</td><td>6</td><td>0.134</td><td>0.065</td><td>0.07</td></tr><tr><td>Drosophila subobscura</td><td>Dro.sub</td><td>22429</td><td>2422</td><td>166.141</td><td>25.753</td><td>46.52</td><td>11716</td><td>871</td><td>87.433</td><td>11.817</td><td>43.73</td></tr><tr><td>Drosophila suzukii</td><td>Dro.suz</td><td>15817</td><td>1035</td><td>117.163</td><td>15.774</td><td>32.80</td><td>13044</td><td>1565</td><td>97.343</td><td>20.359</td><td>48.68</td></tr><tr><td>Drosophila testacea</td><td>Dro.tes</td><td>1</td><td>1</td><td>0.007</td><td>0.007</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila transversa</td><td>Dro.tra</td><td>7</td><td>4</td><td>0.052</td><td>0.032</td><td>0.01</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila tristis</td><td>Dro.tri</td><td>310</td><td>28</td><td>2.296</td><td>0.394</td><td>0.64</td><td>77</td><td>11</td><td>0.575</td><td>0.141</td><td>0.29</td></tr><tr><td>Gitona distigma</td><td>Git.dis</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>4</td><td>1</td><td>0.030</td><td>0.015</td><td>0.01</td></tr><tr><td>Hirtodrosophila cameraria</td><td>Hir.cam</td><td>7</td><td>2</td><td>0.052</td><td>0.022</td><td>0.01</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Hirtodrosophila confusa</td><td>Hir.con</td><td>20</td><td>3</td><td>0.148</td><td>0.048</td><td>0.04</td><td>4</td><td>3</td><td>0.030</td><td>0.024</td><td>0.01</td></tr><tr><td>Leucophenga maculata</td><td>Leu.mac</td><td>8</td><td>2</td><td>0.059</td><td>0.023</td><td>0.02</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Phortica semivirgo</td><td>Pho.sem</td><td>1</td><td>1</td><td>0.007</td><td>0.007</td><td>0.00</td><td>1</td><td>1</td><td>0.007</td><td>0.007</td><td>0.00</td></tr><tr><td>Phortica variegata</td><td>Pho.var</td><td>3</td><td>1</td><td>0.022</td><td>0.013</td><td>0.01</td><td>3</td><td>1</td><td>0.022</td><td>0.013</td><td>0.01</td></tr><tr><td>Scaptodrosophila rufifrons</td><td>Sca.ruf</td><td>28</td><td>5</td><td>0.207</td><td>0.062</td><td>0.06</td><td>54</td><td>8</td><td>0.403</td><td>0.102</td><td>0.20</td></tr></tbody><tfoot><tr><td>Total</td><td></td><td>48217</td><td></td><td></td><td></td><td></td><td>26794</td><td></td><td></td><td></td><td></td></tr></tfoot></table>
<table><thead><tr><th rowspan="2">Species</th><th rowspan="2">Code</th><th colspan="5">RIVER (128 traps)</th><th colspan="5">TOWN (129 traps)</th></tr><tr><th>N ind</th><th>Max</th><th>Mean</th><th>SE</th><th>%</th><th>N ind</th><th>Max</th><th>Mean</th><th>SE</th><th>%</th></tr></thead><tbody><tr><td>Chymomyza amoena</td><td>Chy.amo</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila bifasciata</td><td>Dro.bif</td><td>12</td><td>8</td><td>0.094</td><td>0.064</td><td>0.08</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila busckii</td><td>Dro.bus</td><td>128</td><td>21</td><td>1.000</td><td>0.300</td><td>0.90</td><td>39</td><td>6</td><td>0.302</td><td>0.095</td><td>1.79</td></tr><tr><td>Drosophila funebris</td><td>Dro.fun</td><td>30</td><td>7</td><td>0.234</td><td>0.090</td><td>0.21</td><td>22</td><td>6</td><td>0.171</td><td>0.063</td><td>1.01</td></tr><tr><td>Drosophila helvetica</td><td>Dro.hel</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila hydei</td><td>Dro.hyd</td><td>145</td><td>18</td><td>1.133</td><td>0.227</td><td>1.02</td><td>84</td><td>9</td><td>0.651</td><td>0.134</td><td>3.87</td></tr><tr><td>Drosophila immigrans</td><td>Dro.imm</td><td>764</td><td>129</td><td>5.969</td><td>1.464</td><td>5.38</td><td>134</td><td>18</td><td>1.039</td><td>0.231</td><td>6.17</td></tr><tr><td>Drosophila kuntzei</td><td>Dro.kun</td><td>157</td><td>37</td><td>1.227</td><td>0.443</td><td>1.10</td><td>3</td><td>2</td><td>0.023</td><td>0.017</td><td>0.14</td></tr><tr><td>Drosophila melanogaster</td><td>Dro.mel</td><td>509</td><td>96</td><td>3.977</td><td>1.004</td><td>3.58</td><td>468</td><td>91</td><td>3.628</td><td>0.953</td><td>21.54</td></tr><tr><td>Drosophila obscura</td><td>Droobs</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila phalerata</td><td>Dro.pha</td><td>110</td><td>23</td><td>0.859</td><td>0.295</td><td>0.77</td><td>3</td><td>2</td><td>0.023</td><td>0.017</td><td>0.14</td></tr><tr><td>Drosophila repleta</td><td>Dro.rep</td><td>26</td><td>6</td><td>0.203</td><td>0.069</td><td>0.18</td><td>32</td><td>5</td><td>0.248</td><td>0.070</td><td>1.47</td></tr><tr><td>Drosophila simulans</td><td>Dro.sim</td><td>12</td><td>3</td><td>0.094</td><td>0.038</td><td>0.08</td><td>6</td><td>4</td><td>0.047</td><td>0.033</td><td>0.28</td></tr><tr><td>Drosophila subobscura</td><td>Dro.sub</td><td>6430</td><td>506</td><td>50.234</td><td>8.493</td><td>45.24</td><td>858</td><td>157</td><td>6.651</td><td>1.679</td><td>39.48</td></tr><tr><td>Drosophila suzukii</td><td>Dro.suz</td><td>5676</td><td>699</td><td>44.344</td><td>7.931</td><td>39.94</td><td>516</td><td>131</td><td>4.000</td><td>1.189</td><td>23.75</td></tr><tr><td>Drosophila testacea</td><td>Dro.tes</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila transversa</td><td>Dro.tra</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Drosophila tristis</td><td>Dro.tri</td><td>158</td><td>21</td><td>1.234</td><td>0.288</td><td>1.11</td><td>6</td><td>2</td><td>0.047</td><td>0.022</td><td>0.28</td></tr><tr><td>Gitona distigma</td><td>Git.dis</td><td>2</td><td>2</td><td>0.016</td><td>0.016</td><td>0.01</td><td>2</td><td>1</td><td>0.016</td><td>0.011</td><td>0.09</td></tr><tr><td>Hirtodrosophila cameraria</td><td>Hir.cam</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Hirtodrosophila confusa</td><td>Hir.con</td><td>3</td><td>2</td><td>0.023</td><td>0.017</td><td>0.02</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Leucophenga maculata</td><td>Leu.mac</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Phortica semivirgo</td><td>Pho.sem</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Phortica variegata</td><td>Pho.var</td><td>3</td><td>2</td><td>0.023</td><td>0.017</td><td>0.02</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr><tr><td>Scaptodrosophila rufifrons</td><td>Sca.ruf</td><td>48</td><td>13</td><td>0.375</td><td>0.134</td><td>0.34</td><td>0</td><td>0</td><td>0.000</td><td>0.000</td><td>0.00</td></tr></tbody><tfoot><tr><td>Total</td><td></td><td>14213</td><td></td><td></td><td></td><td></td><td>2173</td><td></td><td></td><td></td><td></td></tr></tfoot></table>
**Suppl. Mat. E** Seasonal distribution of the proportion of individuals of the most abundant Drosophilidae species among the different urban habitats (X-axes: months from September 2018 to August 2019; Y-axes: relative abundance of individuals in percentage between habitats for each month).

<figure><img src="image_16.png" /><figcaption>(b) *Drosophila hydei*</figcaption></figure>

<figure><img src="image_17.png" /></figure>
(c) Drosophila immigrans

<figure><img src="image_18.png" /></figure>

(d) Drosophila kuntzei

<figure><img src="image_19.png" /></figure>

(e) Drosophila melanogaster

<figure><img src="image_20.png" /></figure>
<figure><img src="image_21.png" /><figcaption>(g) *Drosophila subobscura*</figcaption></figure>

<figure><img src="image_22.png" /></figure>
**Suppl. Mat. F** Variation of the number of individuals of the most abundant Drosophilidae species in the different urban habitats over the course of the year (X-axes: months from September 2018 to August 2019; Y-axes: cumulated number of individuals in the four habitats for each month).

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /></figure>
(c) Drosophila immigrans

<figure><img src="image_25.png" /></figure>

(d) Drosophila kuntzei

<figure><img src="image_26.png" /></figure>

(e) Drosophila melanogaster

<figure><img src="image_27.png" /></figure>
<figure><img src="image_28.png" /><figcaption>(g) *Drosophila subobscura*</figcaption></figure>

<figure><img src="image_29.png" /></figure>
**Supp. Mat. G:** meteorological characteristics of the sampling periods. Cumulative temperature (red line): sum of daily mean temperatures (>0°C) of the sampling week (degree-days). Cumulative precipitation (blue histograms): total rainfall for the week of sampling (mm).

<figure><img src="image_30.png" /></figure>
**Supp. Mat. H** Effect of environmental variables on the species richness of Drosophilidae community, the number of Drosophilidae individuals (Drosophila abundance), the number of *D. suzukii* individuals (*D. suzukii* abundance), the number of summer and dark morphs of *D. suzukii* and the wing area index (wing size) of female and male *D. suzukii* per trap analysed by GLM. n = number of traps used in analyses.

**Explanatory variables:** WATER: Cover of water (radius=100m); loBUILD: Cover of building (radius=5m); TREE: Cover of tree layer (radius=5m); SHRUB: Cover of shrub layer (radius=5m); TEMPLOWw: Lowest temperature in the sampling week; NFROSTw: Number of frost days during the sampling week; BUILD: Cover of building (radius=100m); DWOOD: Cover of dead wood debris (radius=5m); loROAD: Cover of road (radius=5m); SRtree: Plant species richness in tree layer (radius=5m); SRshrub: Plant species richness in shrub layer (radius=5m); WOOD: Cover of forest (radius=100m); NFRUIT: Number of fruiting plant species around the trap (radius = 10m); TEMPTOPy: Highest temperature between the 1st January and the day of trap collection; RAINCUMw: Cumulative precipitation during the sampling week; TEMPTOPw: Highest temperature in the sampling week; GARDEN: Cover of private garden (radius=100m); NFROSTy: Number of frost days between the 1st January and the day of trap collection. More details about measured variables are given in the full list of variables (see Supp. Mat. C)
<table><thead><tr><th rowspan="2">Dependent variables</th><th rowspan="2">Explanatory variables</th><th colspan="6">Model parameters</th></tr><tr><th>B</th><th>Standard residual</th><th>Wald χ²</th><th>d.f.</th><th>p</th><th>AIC</th></tr></thead><tbody><tr><td rowspan="7">Drosophila species richness<br>(log₁₀, n = 526)</td><td>Model constant</td><td>0.4895</td><td>0.0302</td><td>262.18</td><td>1</td><td>&lt;0.001</td><td>-333.09</td></tr><tr><td>WATER</td><td>-0.0032</td><td>0.0009</td><td>12.46</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>loBUILD</td><td>-0.0021</td><td>0.0004</td><td>22.57</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>TREE</td><td>0.0013</td><td>0.0003</td><td>25.21</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>SHRUB</td><td>0.0022</td><td>0.0004</td><td>37.39</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>TEMPLOWw</td><td>0.0181</td><td>0.0022</td><td>67.29</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>NFROSTw</td><td>-0.0428</td><td>0.0088</td><td>23.74</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td rowspan="10">Drosophila abundance<br>(log₁₀, n = 526)</td><td>Model constant</td><td>1.7886</td><td>0.0740</td><td>583.77</td><td>1</td><td>&lt;0.001</td><td>811.67</td></tr><tr><td>BUILD</td><td>-0.0046</td><td>0.0014</td><td>10.07</td><td>1</td><td>0.002</td><td></td></tr><tr><td>WATER</td><td>-0.0088</td><td>0.0027</td><td>10.63</td><td>1</td><td>0.001</td><td></td></tr><tr><td>DWOOD</td><td>0.0057</td><td>0.0027</td><td>4.48</td><td>1</td><td>0.034</td><td></td></tr><tr><td>loROAD</td><td>-0.0037</td><td>0.0016</td><td>5.66</td><td>1</td><td>0.017</td><td></td></tr><tr><td>loBUILD</td><td>-0.0086</td><td>0.0016</td><td>29.01</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>SRtree</td><td>0.1012</td><td>0.0256</td><td>15.62</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>SHRUB</td><td>0.0050</td><td>0.0013</td><td>14.57</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>SRshrub</td><td>0.0385</td><td>0.0168</td><td>5.27</td><td>1</td><td>0.022</td><td></td></tr><tr><td>NFROSTw</td><td>-0.2781</td><td>0.0143</td><td>377.42</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td rowspan="9">D. suzukii abundance<br>(log₁₀, n = 526)</td><td>Model constant</td><td>-0.4149</td><td>0.1554</td><td>7.13</td><td>1</td><td>0.008</td><td>936.47</td></tr><tr><td>WOOD</td><td>0.0137</td><td>0.0014</td><td>90.69</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>DWOOD</td><td>0.0085</td><td>0.0029</td><td>8.59</td><td>1</td><td>0.003</td><td></td></tr><tr><td>loBUILD</td><td>-0.0067</td><td>0.0017</td><td>16.22</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>loROAD</td><td>-0.0038</td><td>0.0017</td><td>4.68</td><td>1</td><td>0.030</td><td></td></tr><tr><td>SHRUB</td><td>0.0046</td><td>0.0013</td><td>12.85</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>NFRUIT</td><td>0.0569</td><td>0.0260</td><td>4.79</td><td>1</td><td>0.029</td><td></td></tr><tr><td>TEMPTOPy</td><td>0.0314</td><td>0.0043</td><td>53.99</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>RAINCUMw</td><td>-0.0080</td><td>0.0029</td><td>7.49</td><td>1</td><td>0.006</td><td></td></tr><tr><td>TEMPTOPw</td><td>0.0161</td><td>0.0047</td><td>11.90</td><td>1</td><td>0.001</td><td></td></tr><tr><td rowspan="6">Summer morph abundance<br>(log₁₀, n = 526)</td><td>Model constant</td><td>-0.8741</td><td>0.0843</td><td>107.41</td><td>1</td><td>&lt;0.001</td><td>800.17</td></tr><tr><td>loBUILD</td><td>-0.0056</td><td>0.0012</td><td>20.47</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>SHRUB</td><td>0.0028</td><td>0.0011</td><td>7.10</td><td>1</td><td>0.008</td><td></td></tr><tr><td>NFRUIT</td><td>0.1443</td><td>0.0226</td><td>40.88</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>TEMPTOPy</td><td>0.0120</td><td>0.0032</td><td>13.87</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>TEMPTOPw</td><td>0.0495</td><td>0.0037</td><td>180.32</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td rowspan="6">Dark morph abundance<br>(log₁₀, n = 526)</td><td>Model constant</td><td>-1.2132</td><td>0.1115</td><td>118.46</td><td>1</td><td>&lt;0.001</td><td>852.01</td></tr><tr><td>WOOD</td><td>0.0149</td><td>0.0013</td><td>132.55</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>GARDEN</td><td>0.0124</td><td>0.0036</td><td>12.06</td><td>1</td><td>0.001</td><td></td></tr><tr><td>DWOOD</td><td>0.0055</td><td>0.0027</td><td>4.24</td><td>1</td><td>0.040</td><td></td></tr><tr><td>loBUILD</td><td>-0.0059</td><td>0.0013</td><td>20.31</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td>SHRUB</td><td>0.0036</td><td>0.0012</td><td>9.87</td><td>1</td><td>0.002</td><td></td></tr><tr><td>NFROSTy</td><td>0.0831</td><td>0.0057</td><td>213.86</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td rowspan="3">Wing size of females<br>D. suzukii<br>(n=380)</td><td>Model constant</td><td>3.4860</td><td>0.0503</td><td>4794.38</td><td>1</td><td>&lt;0.001</td><td>159.11</td></tr><tr><td>SRtree</td><td>0.0442</td><td>0.0133</td><td>11.10</td><td>1</td><td>0.001</td><td></td></tr><tr><td>TEMPTOPw</td><td>-0.0177</td><td>0.0020</td><td>76.68</td><td>1</td><td>&lt;0.001</td><td></td></tr><tr><td rowspan="2">Wing size of males<br>D. suzukii<br>(n=328)</td><td>Model constant</td><td>3.0837</td><td>0.0400</td><td>5941.04</td><td>1</td><td>&lt;0.001</td><td>-27.29</td></tr><tr><td>TEMPTOPw</td><td>-0.0229</td><td>0.0018</td><td>166.08</td><td>1</td><td>&lt;0.001</td><td></td></tr></tbody></table>
**Supp. Mat. I** Plant species the most correlated with the abundance of *Drosophila suzukii* over the year (Spearman correlation coefficients, non-significant results are not shown, *: p<0.05, **: p<0.01, ***: p<0.001). Only species present in at least 2% of the sampling plots were selected and samples from the town centre were removed. Layer (vegetation layer): T: tree layer, S: shrub layer, H: herb layer.
<table><thead><tr><th rowspan="2"></th><th rowspan="2">Layer</th><th rowspan="2">Code</th><th colspan="2">SEP (n=39)</th><th colspan="2">OCT (n=41)</th><th colspan="2">NOV (n=43)</th><th colspan="2">DEC (n=43)</th><th colspan="2">FEB (n=33)</th><th colspan="2">MAR (n=42)</th><th colspan="2">MAY (n=44)</th><th colspan="2">JUL (n=44)</th><th colspan="2">AUG (n=45)</th><th colspan="2">Total (n=374)</th></tr><tr><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th><th>R</th><th>p</th></tr></thead><tbody><tr><td colspan="21">(a) Species positively correlated with D. suzukii</td></tr><tr><td>Acer pseudoplatanus</td><td>T</td><td>Ace.pseT</td><td></td><td></td><td></td><td></td><td>0.544 ***</td><td>0.706 ***</td><td>0.726 ***</td><td>0.679 ***</td><td>0.302 *</td><td>-0.305 *</td><td>0.439 **</td><td>0.184 ***</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Fraxinus excelsior</td><td>T</td><td>Fra.excT</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.357 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Hedera helix</td><td>T</td><td>Hed.helT</td><td></td><td></td><td></td><td></td><td>0.608 ***</td><td>0.769 ***</td><td>0.649 ***</td><td>0.513 ***</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Salix sp.</td><td>T</td><td>Sal.spT</td><td>0.374 *</td><td>0.316 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ulmus minor</td><td>T</td><td>Ulm.minT</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Acer pseudoplatanus</td><td>S</td><td>Ace.pseS</td><td></td><td></td><td>0.325 *</td><td>0.389 ***</td><td>0.455 **</td><td>0.401 *</td><td>0.609 ***</td><td></td><td>-0.370 *</td><td>0.488 ***</td><td>0.237 ***</td><td>0.134 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Cornus sanguinea</td><td>S</td><td>Cor.sanS</td><td></td><td></td><td></td><td>0.507 ***</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Corylus avellana</td><td>S</td><td>Cor.aveS</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.320 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Crataegus monogyna</td><td>S</td><td>Cra.monS</td><td></td><td></td><td></td><td></td><td>0.379 *</td><td>0.348 *</td><td></td><td></td><td></td><td>0.319 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Fraxinus excelsior</td><td>S</td><td>Fra.excS</td><td>0.341 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Hedera helix</td><td>S</td><td>Hed.helS</td><td></td><td></td><td></td><td></td><td>0.516 ***</td><td>0.734 ***</td><td>0.718 ***</td><td>0.569 ***</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Prunus avium</td><td>S</td><td>Pru.aviS</td><td></td><td></td><td></td><td></td><td></td><td>0.323 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Rubus fructicosus</td><td>S</td><td>Rub.fruS</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.423 **</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sambucus nigra</td><td>S</td><td>Sam.nigS</td><td></td><td></td><td></td><td></td><td></td><td>0.494 ***</td><td>0.654 ***</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ulmus minor</td><td>S</td><td>Ulm.minS</td><td></td><td></td><td></td><td></td><td></td><td>0.515 ***</td><td></td><td></td><td>0.387 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Acer pseudoplatanus</td><td>H</td><td>Ace.pseH</td><td></td><td>0.375 *</td><td>0.571 ***</td><td>0.636 ***</td><td></td><td></td><td></td><td>0.448 **</td><td>0.378 *</td><td></td><td></td><td>0.356 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Arum macalatum</td><td>H</td><td>Aru.macH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.393 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Carex sylvatica</td><td>H</td><td>Car.sylH</td><td></td><td></td><td></td><td></td><td>0.387 **</td><td>0.484 **</td><td>0.565 ***</td><td></td><td>0.333 *</td><td></td><td></td><td>0.337 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Cornus sanguinea</td><td>H</td><td>Cor.sanH</td><td>0.427 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.353 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Corylus avellana</td><td>H</td><td>Cor.aveH</td><td></td><td></td><td></td><td>0.339 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.345 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Equisetum arvense</td><td>H</td><td>Equ.arvH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Fraxinus excelsior</td><td>H</td><td>Fra.excH</td><td></td><td></td><td></td><td>0.351 *</td><td></td><td></td><td></td><td></td><td></td><td>0.355 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Geum urbanum</td><td>H</td><td>Geu.urbH</td><td></td><td></td><td></td><td>0.376 *</td><td>0.533 ***</td><td>0.522 **</td><td>0.479 ***</td><td>0.456 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Hedera helix</td><td>H</td><td>Hed.helH</td><td></td><td></td><td></td><td>0.626 ***</td><td>0.702 ***</td><td>0.553 ***</td><td>0.649 ***</td><td>0.419 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.124 *</td><td></td></tr><tr><td>Ranunculus ficaria</td><td>H</td><td>Ran.ficH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.126 *</td><td></td></tr><tr><td>Ribes rubrum</td><td>H</td><td>Rib.rubH</td><td></td><td></td><td>0.316 *</td><td></td><td></td><td>0.367 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Rubus caesius</td><td>H</td><td>Rub.caH</td><td></td><td></td><td></td><td></td><td>0.630 ***</td><td>0.525 **</td><td>0.508 ***</td><td>0.353 *</td><td></td><td></td><td></td><td>0.377 *</td><td></td><td>0.121 *</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sambucus nigra</td><td>H</td><td>Sam.nigH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.427 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Ulmus minor</td><td>H</td><td>Ulm.minH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.341 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Veronica hederifolia</td><td>H</td><td>Ver.hedH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>0.343 *</td><td>0.439 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td colspan="21">(b) Species negatively correlated with D. suzukii</td></tr><tr><td>Platanus acerifolia</td><td>T</td><td>Pla.aceT</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Populus sp.</td><td>T</td><td>Pop.spT</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.369 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.124 *</td><td></td></tr><tr><td>Salix sp.</td><td>S</td><td>Sal.spS</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.345 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.144 **</td><td></td></tr><tr><td>Agrostis stolonifera</td><td>H</td><td>Agr.stoH</td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.457 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.125 *</td><td></td></tr><tr><td>Angelica sylvestris</td><td>H</td><td>Ang.sylH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.359 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.138 **</td><td></td></tr><tr><td>Anthriscus sylvestris</td><td>H</td><td>Ant.sylH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.114 *</td><td></td></tr><tr><td>Arrhenatherum eliatus</td><td>H</td><td>Arr.eliH</td><td></td><td></td><td></td><td></td><td></td><td>-0.458 **</td><td></td><td>-0.400 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.222 ***</td><td></td></tr><tr><td>Artemisia vulgaris</td><td>H</td><td>Art.vulH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.336 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Bellis perennis</td><td>H</td><td>Bel.perH</td><td></td><td></td><td></td><td></td><td>-0.462 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.228 ***</td><td></td></tr><tr><td>Bryonia dioica</td><td>H</td><td>Bry.dioH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.132 **</td><td></td></tr><tr><td>Capsella bursa-pastoris</td><td>H</td><td>Cap.burH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.178 ***</td><td></td></tr><tr><td>Cardamine hirsuta</td><td>H</td><td>Car.hirH</td><td></td><td></td><td></td><td></td><td></td><td>-0.402 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.207 ***</td><td></td></tr><tr><td>Carex acutiformis</td><td>H</td><td>Car.acuH</td><td></td><td></td><td></td><td></td><td>0.378 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Carex hirta</td><td>H</td><td>Car.hirtH</td><td>-0.336 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Chelidonium majus</td><td>H</td><td>Che.majH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.307 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.114 *</td><td></td></tr><tr><td>Cirsium arvense</td><td>H</td><td>Cir.arvH</td><td></td><td></td><td>-0.368 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Conyza canadensis</td><td>H</td><td>Con.canH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.306 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.115 *</td><td></td></tr><tr><td>Cotoneaster sp.</td><td>H</td><td>Cot.spH</td><td></td><td></td><td></td><td></td><td></td><td>-0.423 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.171 ***</td><td></td></tr><tr><td>Dactylis glomerata</td><td>H</td><td>Dac.gloH</td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.402 *</td><td>-0.431 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.117 *</td><td></td></tr><tr><td>Festuca rubra</td><td>H</td><td>Fes.rubH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.333 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.186 ***</td><td></td></tr><tr><td>Galium aparine</td><td>H</td><td>Gal.apaH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.215 ***</td><td></td></tr><tr><td>Geranium molle</td><td>H</td><td>Ger.molH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.157 **</td><td></td></tr><tr><td>Glechoma hederacea</td><td>H</td><td>Gle.hedH</td><td></td><td></td><td></td><td></td><td>-0.364 *</td><td></td><td>-0.322 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.180 ***</td><td></td></tr><tr><td>Heracleum spondylium</td><td>H</td><td>Her.spoH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.143 **</td><td></td></tr><tr><td>Holcus lanatus</td><td>H</td><td>Hol.lanH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.311 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.106 *</td><td></td></tr><tr><td>Lapsana communis</td><td>H</td><td>Lap.comH</td><td>-0.311 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.107 *</td><td></td></tr><tr><td>Lolium perenne</td><td>H</td><td>Lol.perH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.438 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.226 ***</td><td></td></tr><tr><td>Malva sylvestris</td><td>H</td><td>Mal.sylH</td><td></td><td></td><td>-0.322 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Mercurialis annua</td><td>H</td><td>Mer.annH</td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.356 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.161 **</td><td></td></tr><tr><td>Plantago lanceolata</td><td>H</td><td>Pla.lanH</td><td>-0.351 *</td><td></td><td></td><td></td><td>-0.347 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.146 **</td><td></td></tr><tr><td>Poa annua</td><td>H</td><td>Poa.annH</td><td></td><td></td><td>-0.313 *</td><td>-0.355 *</td><td></td><td></td><td>-0.354 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.266 ***</td><td></td></tr><tr><td>Poa trivialis</td><td>H</td><td>Poa.triH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.164 ***</td><td></td></tr><tr><td>Ranunculus repens</td><td>H</td><td>Ran.repH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.138 **</td><td></td></tr><tr><td>Solanum dulcamara</td><td>H</td><td>Sol.dulH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.307 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sonchus oleraceus</td><td>H</td><td>Son.oleH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.121 *</td><td></td></tr><tr><td>Stellaria media</td><td>H</td><td>Ste.medH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.140 **</td><td></td></tr><tr><td>Taraxacum officinale</td><td>H</td><td>Tar.offH</td><td>-0.325 *</td><td>-0.316 *</td><td></td><td></td><td>-0.481 ***</td><td></td><td>-0.558 ***</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.241 ***</td><td></td></tr><tr><td>Trifolium repens</td><td>H</td><td>Tri.repH</td><td></td><td>-0.326 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.395 **</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Urtica dioica</td><td>H</td><td>Urt.dioH</td><td></td><td></td><td></td><td></td><td>-0.366 *</td><td></td><td>-0.311 *</td><td>-0.368 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Veronica persica</td><td>H</td><td>Ver.perH</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.311 *</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>-0.126 *</td><td></td></tr></tbody></table>
**Supp. Mat. J:** Differences in wing sizes (± SE, wing area index in mm²) between morph categories (summer, intermediate and winter morphs) of *Drosophila suzukii* females (a) and males (b). The number of individuals used for wing trait measurements is indicated in italic above the histograms. The wing size was significantly different between morph categories in females (F = 90.456, p < 0.001, ddl = 2) and males (F = 104.159, p < 0.001, ddl = 2).

<figure><img src="image_31.png" /><figcaption>(b)</figcaption></figure>

<figure><img src="image_32.png" /></figure>
**Supp. Mat. K:** Differences in wing sizes (wing area index in mm², mean ± SE) between urban habitats (forest, park, riverside, town centre) of *Drosophila suzukii* females (a) and males (b). The number of fly individuals used for wing size measurements is indicated in italic above histograms. The wing size was significantly different between habitats in females (F = 10.739, p < 0.001, ddl = 3) and males (F = 3.108, p = 0.026, ddl = 3). Letters above histograms indicate significative differences between habitats.

<figure><img src="image_33.png" /><figcaption>(b)</figcaption></figure>

<figure><img src="image_34.png" /></figure>