DOI: 10.5061/dryad.dr7sqvb3c
title: Data from: Effects of the control of an invasive tree on the structure of a plant-frugivore network

description: Invasive non-native species are one of the main causes of degradation of
 ecosystems worldwide. The control of invasive species is key to reduce
 threats to ecosystem viability in the long-term. Observations of
 structural changes in ecological interaction networks following invasive
 species suppression can be useful to monitor the success of ecological
 restoration initiatives. We evaluated the structure of plant-bird
 frugivory interaction networks in a plant community invaded by the guava
 tree (Psidium guajava L.) by comparing network metrics before and after
 control actions. Psidium guajava was relevant in all metrics for the
 unmanaged network in this study, with high degree centrality and high
 nestedness contribution. Based on the asymmetry of species interactions,
 we found that birds were highly dependent on the invasive plant before
 suppression. Once P. guajava trees were eliminated, bird and plant species
 richness, total number of interactions, and modularity increased, whereas
 nestedness and interaction strength asymmetry decreased. The diet of the
 bird community became more diversified once P.
 guajava was no longer available and relevant species roles in
 community structure emerged. Our results corroborate the fact that
 ecological restoration interventions should include the control of
 non-native plant species that attract frugivorous animals in order to
 diversify plant-frugivore interactions and thus maintain biodiversity in
 natural ecosystems.
description: We conducted the study in the Caieira Natural Municipal Park
 (CNMP), a protected area that covers 1.27 km² (Joinville, state of Santa
 Catarina, southern Brazil) (26°18’24”S, 48°47’36”W) (Figure 1a).  The
 climate is subtropical, constantly humid, with hot summers and no dry
 season, and average maximum temperatures between 26.0 and 27.6º C (Cfa
 type in the Köppen classification; Joinville, 2021). The vegetation cover
 of the CNMP is represented by two forest types: coastal forest
 (<em>restinga arbórea, in Portuguese</em>) and mangrove
 (Joinville, 2021), both in the Atlantic Forest domain, an important global
 biodiversity hotspot (Myers et al., 2000) (Figure 1a,b).  The park grants
 public access to landscaped areas and trails.
 Non-native species were planted in a small orchard in the park
 between 1970 and 2004. Some of those trees, such as guava
 (<em>Psidium guajava</em>), avocado (<em>Persea
 americana</em>), and star fruit (<em>Averrhoa
 carambola</em>), still bear fruit in the area (Preis, 2020). Several
 invasive non-native plants have established populations in the park, and
 are listed in the management plan for control by park managers (Joinville,
 2021). An established population of <em>P. guajava</em> trees
 was present both in landscaped areas and in <em>restinga</em>
 and mangrove remnants, totaling around 410 individuals per km².
 <em> Psidium guajava</em> is a shrub or tree in the
 Myrtaceae family, up to 12 m in height, with smooth, scaly, reddish-brown
 bark. Fruits are globular to pyriform, 2–8 cm long, green to yellow, with
 pink, yellow, or white pulp (Landrum & Mitra, 2021).
 <em>Psidium guajava</em> can produce fruits throughout the
 year, especially in the summer months (Landrum & Mitra, 2021), but
 fruit phenology varies according to the species variety and water
 availability (Moura, 2001). In the study area, fruiting occurred between
 late summer to autumn (February to April; BM, personal observation). The
 main forms of dispersal are zoochory and anthropochory (Arévalo-Marín et
 al., 2021; Heleno et al., 2013b). The species is an important node in its
 introduced range both in pollination networks in Galapagos (see Traveset
 et al., 2015) and plant–frugivore networks in Galápagos, South Africa and
 Brazil (see Baltzinger et al., 2020; Heleno et al., 2013b; Silva &
 Pizo, 2020). The origin of <em>P.
 guajava</em> is uncertain, but several authors suggest that it
 originated between northern South America and Central America
 (Arévalo-Marín et al., 2021). More recent studies indicate that it may
 have originated in the savannas and semi-deciduous forests of South
 America (Landrum & Mitra, 2021) or in the humid Chaco and/or
 Cerrado (Arévalo-Marín et al., 2021). <em>Psidium guajava</em>
 is widely cultivated in several countries and considered invasive in
 several tropical and subtropical regions of the world (Landrum &
 Mitra, 2021; Richardson & Rejmánek, 2011), such as East Africa
 (Witt & Luke, 2017), North America (Acevedo-Rodríguez &
 Strong, 2012), Brazil (Sampaio & Schmidt, 2013; Ziller &
 Dechoum, 2013) and the Galápagos Islands in Ecuador (Guézou et al., 2010;
 Urquía et al., 2019). Use by human populations very likely increased its
 distribution in the past (Arévalo-Marín et al., 2021). As an invasive
 species, it can form dense stands that displace native vegetation (Leão et
 al., 2011); thus, the balance between valuable fruit production and
 invasive potential requires careful monitoring (Landrum & Mitra,
 2021) and continuous control. <em>Data collection
 of frugivory interactions</em> We collected data
 in the CNMP between February and April of 2021 and 2022, when <em>P.
 guajava</em> trees were fruiting in 2021, and in the same timeframe
 after <em>P. guajava</em> suppression, in 2022. We carried out
 thirty field surveys each year. In each survey, the same trail was covered
 by two observers in early morning hours (6:45 am ± 15 min until 10:00 am ±
 30 min) or in the afternoon (4:00 pm ± 15 min and 6:30 pm ± 30 min) (Pizo
 & Galetti, 2010).  The trails mainly covered landscaped areas and
 <em>restinga</em> vegetation (Figure 1a). In addition, we
 defined three observation areas (Figure 1c), where two observers kept
 watch together for 20 minutes (Jordano & Schupp, 2000). Each
 observer recorded all avian frugivory events on fruiting plants with a
 pair of binoculars (Leitz Wetzlar Trinovid 10x40) and a digital camera
 (Sony DSC-HX300 and Nikon Coolpix p510). Walking direction along the trail
 and order of observation areas were alternated on sampling days on each
 field survey to ensure that all study site areas were observed at
 different times of day. We carried out data collection at the same period
 of time over two consecutive years to ensure sampling consistency
 regarding the presence of migratory birds and fructification of the
 sampled plant species. We performed a nonparametric Wilcox test to verify
 whether the hours of observation in each year were different between
 years. The dependent variable was the duration of observation (in minutes)
 at every fortnight and the independent variable was sampling year. We used
 the iNEXT function from the iNEXT package to assess community diversity
 and build species accumulation curves (Hsieh, Ma, & Chao, 2022),
 using abundance data to estimate bird and plant diversity based on the
 Shannon index (q = 1). We conducted the analysis using R 3.6.2 software (R
 core Team, 2022). We used the following parameters to
 record frugivory interactions by birds (feeding bouts): the plant species
 on whose fruits a bird was feeding, and the respective bird species. A new
 frugivory event was counted if the bird left the tree, and then returned.
 The number of fruits/seeds ingested per visit was not counted. Bird
 foraging flocks were recorded as separate interactions per individual.
 Bird identification was mostly carried out in the field, but we consulted
 experts and literature in case of uncertainty. Scientific nomenclature
 follows the Brazilian Committee of Ornithological Records (Pacheco et al.,
 2021). Likewise, plants not identified in the field were identified with
 help from experts who reviewed photographic records. The nomenclature of
 plant species is based on the “Flora e Funga do Brasil” database
 (2022). <em>Psidium guajava control
 campaigns</em> We conducted two <em>P.
 guajava</em> control campaigns in the CNMP. In October 2021, control
 mainly focused on adults and reproductive individuals, but also included
 small plants in the surroundings of eliminated adults. We eliminated a
 total of 435 plants. In May 2022, one month after the sampling period, a
 follow-up expedition took place, in which we eliminated 85
 non-reproductive plants as well as resprouted plants. Altogether, we cut
 down about 520 <em>P. guajava </em>trees in the area. We cut
 close to ground level with a chainsaw, followed by immediate spraying of a
 6% Garlon 480BR (Triclopyr active ingredient) solution on the stump
 (Dechoum & Ziller, 2013). Once regrowth was observed, we carried
 out a re-check with foliar application of a 2% Glyphosate solution. During
 the second field survey, one fruiting <em>P. guajava</em> tree
 was found, so we eliminated all fruits, the tree was later cut down, and
 the stump treated. <em>Network metrics
 </em> We organized the interactions observed
 during each year into quantitative matrices (i=plant species; j=bird
 species) based on the frequency of frugivory events observed in the CNMP.
 Two data matrices were built: the first one, entitled “unmanaged
 community”, referred to the plant community invaded by <em>P.
 guajava</em> in 2021, prior to the control intervention; the second
 one, entitled “managed community”, corresponded to the same community
 after control, in 2022. Both quantitative networks were built and analyzed
 using the Bipartite package (Dormann et al., 2009) in software R, version
 3.6.2 (R core Team 2022). We calculated sampling completeness of species
 interactions using Chao1 as a richness estimator and the SCw1 function
 (Macgregor et al., 2017). We evaluated the following
 network-level metrics, then contrasted them with those from null models
 for significance assessments: quantitative nestedness (weighted NODF;
 Almeida-Neto & Ulrich, 2011), quantitative modularity (DIRTLPAwb+
 algorithm; Beckett, 2016), and interaction strength asymmetry (ISA;
 Dormann et al., 2008). We used Z-scores to assess significance of
 nestedness and modularity with null-model functions by comparing the
 results obtained with the observed values, using the methods vaznull and
 method r2d, respectively, with 999 randomizations each. We also used the
 null.t.test with 999 randomizations to obtain the significance of
 interaction strength asymmetry (Dormann et al., 2008). Interaction
 strength asymmetry varies between −1 and 1, with positive values
 indicating high dependence of an animal on a plant species, and negative
 values indicating the opposite (Blüthgen et al., 2007).
 We evaluated the following species-level metrics: plant species
 degree centrality (Martín-González et al., 2010), plant species nestedness
 contribution, asymmetry of plant species interactions using the push-pull
 index (Vázquez et al., 2007) and participation coefficients (c-values),
 and within-module degree (z-values) for network modules (Olesen et al.,
 2007). Degree centrality takes the number of links of each node (k) into
 account. The push-pull index indicates the direction of interaction
 asymmetry based on dependency; positive values indicate that a species
 more strongly affects the species of the other level with which it
 interacts than vice versa (“pusher”), while negative values indicate that
 a species is, on average, more strongly affected by its interaction
 partners than it affects them (“being pulled”) (Vázquez et al., 2007). The
 cz-values were evaluated for both plant and bird species. We calculated
 the thresholds for participation coefficients and within-module degree for
 each network level (null models with 95% confidence intervals) and used
 them to identify the topological role of each species (network hub, module
 hub, connector, or peripheral; Olesen et al., 2007).
description: # Data from: Effects of the control of an invasive tree on the structure
 of a plant-frugivore network GENERAL INFORMATION 1. Title of Dataset:
 Effects of the control of an invasive tree on the structure of a
 plant-frugivore network 2. Author Information Corresponding Investigator
 Name: Ms Brisa Marciniak Institution: Universidade Federal de Santa
 Catarina, Florianopolis, Brazil Email:
 [brisamarciniak@gmail.com](mailto:brisamarciniak@gmail.com)
 Co-investigator 1 Name: Dr Nivaldo Peroni Institution: Universidade
 Federal de Santa Catarina, Florianopolis, Brazil Co-investigator 2 Name:
 Dr Anna Traveset Institution: Mediterranean Institute of Advanced Studies,
 Esporles, Spain Co-investigator 3 Name: Dr Michele de Sá Dechoum
 Institution: Universidade Federal de Santa Catarina, Florianopolis, Brazil
 3. Date of data collection: Febrary to April 2021 and Febrary to April
 2022 4.Geographic location of data collection: Parque Natural Municipal da
 Caieira, Joinville, Brazil. Give a brief summary of dataset contents,
 contextualized in experimental procedures and results. 1. Recommended
 citation for this dataset: Marciniak, Brisa et al. (2024) Data from:
 Effects of the control of an invasive tree on the structure of a
 plant-frugivore network. Dryad Digital Repository,
 [https://doi.org/10.5061/dryad.dr7sqvb3c](https://doi.org/10.5061/dryad.dr7sqvb3c) 2. Description of the data These data were generated to evaluate the structure of plant-bird frugivory interaction networks in a plant community invaded by the guava tree (*Psidium guajava* L.) by comparing network metrics before and after control actions. 1. File structure File 1 Name: Campos 2021 ceto.txt Description: Quantitative matrix with the frequency of frugivory events observed in the CNMP on 2021 (Unmanaged community). File 2 Name: Campos 2022 ceto.txt Description: Quantitative matrix with the frequency of frugivory events observed in the CNMP on 2022 (Managed community). File 3 Name: R codes.txt Description: Script with all codes used in this study. File 4 Name: curva1total.csv Description: Matrix with frugivory events abundance by bird species observed in the CNMP on 2021 (Unmanaged community). File 5 Name: curva2total.csv Description: Matrix used to rarefaction curves with frugivory events abundance by bird species observed in the CNMP on 2022 (Managed community). File 6 Name: curva1p.csv Description: Matrix used to rarefaction curves with abundance of received interactions by plant species observed in the CNMP on 2021 (Unmanaged community). File 7 Name: curva2p.csv Description: Matrix used to rarefaction curves with abundance of received interactions by plant species observed in the CNMP on 2022 (Managed community). File 8 Name: ano1.csv Description: Quantitative matrix used to sampling completeness with the frequency of frugivory events observed in the CNMP on 2021 (Unmanaged community). File 9 Name: ano2.csv Description: Quantitative matrix used to sampling completeness with the frequency of frugivory events observed in the CNMP on 2022 (Managed community).