DOI: 10.5061/dryad.ns1rn8q0w
title: Distance functions of carabids in crop fields depend on functional traits, crop type and adjacent habitat: a synthesis

description: Natural pest and weed regulation are essential for agricultural
 production, but the spatial distribution of natural enemies within crop
 fields and its drivers are mostly unknown. Using 28 datasets comprising
 1,204 study sites across eight Western and Central European countries, we
 performed a quantitative synthesis of carabid richness, activity densities
 and functional traits in relation to field edges (i.e. distance
 functions). We show for the first time that distance functions of carabids
 strongly depend on carabid functional traits, crop type and, to a lesser
 extent, adjacent non-crop habitats. Richness of both predators and
 granivores and activity densities of small and granivorous species
 decreased towards field interiors, whereas the densities of large species
 increased. We found strong distance decays in maize and vegetables whereas
 richness and densities remained more stable in cereals, oilseed crops and
 legumes. We conclude that carabid assemblages in agricultural landscapes
 are driven by the complex interplay of crop types, adjacent non-crop
 habitats and further landscape parameters with great potential for
 targeted agroecological management. In particular, our synthesis indicates
 that a higher edge-interior ratio can counter the distance decay of
 carabid richness per field and thus likely benefits natural pest and weed
 regulation, hence contributing to agricultural sustainability.
description: # Distance functions of carabids in crop fields depend on functional
 traits, crop type and adjacent habitat: a synthesis
 Our dataset is a synthesis
 of 28 studies, comprising 1204 study sites, reporting carabid beetle
 sampling data as a function of distance from field edge. ## Description of
 the data and file structure The data files included are different
 summaries of the 28 constituent datasets synthesized in this study, each
 corresponding to one or more modeling workflows (see below). These are
 saved as .rds file to be imported in R via readRDS(). 1. **meta_rich**:
 plot-level carabid richness by distance 1. *study*: study from which the
 data come 2. *site*: site identity 3. *richness*: carabid species richness
 4. *crop*: crop grown in field from which samples were taken 5.
 *crop.poo*l: crop pooled into larger categories 6. *snh.type*: type of
 habitat adjacent to focal field 7. *distance100*: distance from field edge
 in units of 100 m 8. *trap.days*: total days traps were deployed * number
 of traps deployed 9. *trap.days10*: trap days in units of 10 10.
 *log.trap.days*: log-transformed trap days 11. *country*: country in which
 study was conducted 12. *distances.sampled.site*: number of unique
 distances from field edge sampled for a given site 13.
 *distances.sampled.study*: number of unique distances from field edge
 sampled for a given study 14. *europe*: whether study was conducted in
 Europe 2. **meta_rich_predatory2**: plot-level carabid richness by
 distance, predatory species only (variables identical to those in
 meta_rich) 3. **meta_rich_granivorous**: plot-level carabid richness by
 distance, granivorous species only (variables identical to those in
 meta_rich) 4. **meta_rich_omnivorous2**: plot-level carabid richness by
 distance, omnivorous species only (variables identical to those in
 meta_rich) 5. **meta_rich_omnivorous3**: plot-level carabid richness by
 distance, omnivorous species only, minus P. cupreus (variables identical
 to those in meta_rich) 6. **meta_abund**: plot-level carabid activity
 density by distance 1. *abund*: total number of beetles caught (i.e.
 activity density) 2. *abund.std*: number of beetles caught per trap day
 (other variables identical to those in meta_rich) 7. **meta_abund_diet2**:
 plot-level carabid activity density by distance, by diet class 1. *diet*:
 diet class --- predatory, omnivorous, or granivorous (other variables
 identical to those in meta_abund) 8. **meta_abund_diet3**: plot-level
 carabid activity density by distance, by diet class minus P. cupreus
 (variables identical to those in meta_abund_diet2) 9. **meta_abund_size**:
 plot-level carabid activity density by distance, by size class 1.
 *size.class*: category of beetle size --- small, medium, or large (other
 variables identical to those in meta_abund) The model files are the R
 objects produced by our Bayesian hierarchical models, and they serve as
 input to the analytical workflows noted below. 1. **brm_rich_00**: model
 of carabid richness by distance 2. **brm_rich_11**: model of carabid
 richness by distance, predatory species only 3. **brm_rich_12**: model of
 carabid richness by distance, omnivorous species only 4. **brm_rich_12b**:
 model of carabid richness by distance, omnivorous species only, minus P.
 cupreus 5. **brm_rich_20**: model of carabid richness by distance,
 granivorous species only 6. **brm_abund_00**: model of carabid activity
 density by distance 7. **brm_abund_11**: model of carabid activity density
 by distance, predatory species only 8. **brm_abund_12**: model of carabid
 activity density by distance, omnivorous species only 9.
 **brm_abund_12b**: model of carabid activity density by distance,
 omnivorous species only, minus P. cupreus 10. **brm_abund_20**: model of
 carabid activity density by distance, granivorous species only 11.
 **brm_abund_30**: model of carabid activity density by distance, small
 species only 12. **brm_abund_40**: model of carabid activity density by
 distance, medium species only 13. **brm_abund_50**: model of carabid
 activity density by distance, large species only ## Code/Software
 Supplementary files ESM1, ESM2, ESM3, and ESM4 provide data summaries and
 R scripts to reproduce fully all analyses and visualizations reported in
 the text of our paper.