DOI: 10.5061/dryad.9p8cz8ww2
title: Host plant richness and abundance drive populations of a super-generalist xylem-feeding insect - Raw data

description: Due to their wide diet breadth, generalist herbivores are often less
 sensitive to bottom-up forces compared to specialists. Despite this, some
 generalist insects can be significantly affected by the diversity and
 structure of the plant communities. Here, we investigated the effect of
 habitat and plant richness on the abundance of the super-generalist meadow
 spittlebug, Philaenus spumarius (Hemiptera: Aphrophoridae). We sampled 93
 sites representing four habitat types (olive groves, vineyards, meadows,
 and field margins) across eight heterogeneous agricultural landscapes in
 central Italy. Nymphs were sampled by quadrat sampling in April along with
 the herbaceous vegetation community, while adults were sampled using a
 sweep net in June, August, and October. Nymph abundance was positively
 associated with plant richness and vegetation cover at a small scale (2
 m2), a scale consistent with the limited movement capability of nymphs,
 while it did not differ between habitat types. A positive correlation
 between adult and juvenile densities was also observed. However, this
 effect weakened towards the end of the growing season. The findings
 indicate that bottom-up effects associated with plant community
 composition can significantly influence the local abundance of a
 super-generalist xylem-feeding insect. The positive relationship between
 plant species richness and nymph abundance suggests that broad host use
 does not necessarily buffer P. spumarius from local vegetation effects.
 Furthermore, the marked weakening of the juvenile–adult abundance
 relationship is consistent with increased dispersal activity happening in
 the fall in our study area. Given that P. spumarius exhibits variation in
 host use and population dynamics across its geographic range, the strength
 of bottom-up effects in this species, as well as its dispersal patterns,
 are likely context-dependent and may vary across environmental and
 geographical settings.
description: Sampling Methods Juveniles (Nymphs)
 Sampling period: late April 2022.<br> Method: quadrat
 sampling along 20 m transects positioned diagonally across each
 site.<br> Replicates: five quadrats (2 m² each) per site.
 All nymphs within each quadrat were counted.
 Vegetation variables recorded per quadrat: 
 vegetation cover (%) vegetation height
 (cm) plant richness (counts of species, genera and
 families) Adults Sampling periods: late
 June, mid-August, mid-October 2022.<br> Method: sweep net
 sampling.<br> Sampling effort: 80 sweeps on ground vegetation + 180
 sweeps on woody canopy vegetation of each plot. Counts
 are provided separately by sampling position (ground vs canopy).
 No pest control or vegetation management targeting <em>P.
 spumarius</em> was applied in sampled habitats.
description: # Host plant richness and abundance drive populations of a
 super-generalist xylem-feeding insect - Raw data Dataset DOI:
 [10.5061/dryad.9p8cz8ww2](https://doi.org/10.5061/dryad.9p8cz8ww2) ##
 Description of the data and file structure This dataset contains field
 sampling data on the meadow spittlebug, *Philaenus spumarius*, collected
 in eight agricultural landscapes in the Abruzzo region (central Italy).
 The data include counts of juveniles and adults, together with information
 on vegetation structure and plant richness. The dataset is intended to
 support ecological and agroecological analyses of *P. spumarius*
 population dynamics and habitat associations, with relevance for pest and
 vector management. #### Time period and location Temporal coverage: April,
 June, August, and October 2022 Geographic coverage: Abruzzo region, Italy
 Habitat types: olive groves, meadows, vineyards, cultivated field margins
 ### Files and variables ### Data Files All files are provided in
 comma-separated values (.csv) format without formatting, merged cells,
 formulas, or filters. #### 1. Juveniles.csv Replicate-level quadrat
 observations (2 m²).\ Each row represents one quadrat. Key variables: *
 Landscape_id: landscape identifier * Site_id: sampling site identifier
 among each landscape * Replicate_id: 2 m² quadrat replicate identifier
 (1–5) among each site * Habitat_type: habitat category *
 Philaenus_spumarius_count: number of nymphs (count) recorded within the
 quadrat * Vegetation_cover_percentage: herbaceous vegetation cover (%)
 recorded within the quadrat * Vegetation_height_cm: herbaceous vegetation
 height (cm) recorded within the quadrat * Plant_species_count: number of
 herbaceous plant species (count) recorded within the quadrat *
 Plant_genera_count: number of herbaceous plant genera (count) recorded
 within the quadrat * Plant_families_count: number of herbaceous plant
 families (count) recorded within the quadrat #### 2. Juveniles_merged.csv
 Plot-level aggregated data derived from juveniles.csv.\ Each row
 represents one sampling site. Key variables: * Landscape_id: landscape
 identifier * Site_id: sampling site identifier among each landscape *
 Habitat_type: habitat category * Philaenus_spumarius_count: number of
 nymphs (count) recorded within the site * Vegetation_cover_percentage:
 mean herbaceous vegetation cover (%) recorded within the site *
 Vegetation_height_cm: mean herbaceous vegetation height (cm) recorded
 within the site * Plant_species_count: total number of herbaceous plant
 species (count) recorded within the site * Plant_genera_count: total
 number of herbaceous plant genera (count) recorded within the site *
 Plant_families_count: total number of herbaceous plant families (count)
 recorded within the site #### 3. Juveniles_and_adults.csv Plot-level
 seasonal sampling including juveniles and adults. Each row represents one
 site × sampling month × life stage × position. Key variables: *
 Landscape_id: landscape identifier * Site_id: sampling site identifier
 among each landscape * Habitat_type: habitat category * Sampling_round:
 sampling rounds in chronological order (A-D) * Sampling_month: sampling
 round months (April, June, August, October) * Life_stage: sampled life
 stage (juvenile, adult) * Position: sampling position (ground, canopy) *
 Philaenus_spumarius_count: number of P. spumarius (count) recorded ###
 Missing Values In **3. Juveniles_and_adults.csv**, NA occurs in rows
 corresponding to juveniles on canopy vegetation. These NA values can be
 interpreted as 0 for analysis, because *Philaenus spumarius* only develop
 on ground vegetation. ## Legal and Ethical Statement The dataset does not
 contain information on human subjects.