DOI: 10.5061/dryad.2547d7wz8
title: Dryland state transitions alter trophic interactions in a predator-prey system

description: Environmental change is expected to alter trophic interactions and
 food-web dynamics with consequences for ecosystem structure, function, and
 stability. However, the mechanisms by which environmental change
 influences top-down and bottom-up processes are poorly documented. Here,
 we examined how environmental change caused by shrub encroachment affects
 trophic interactions in a dryland. The predator-prey system included an
 apex canid predator (coyote; Canis latrans), an intermediate
 canid predator (kit fox; Vulpes macrotis), and two herbivorous lagomorph
 prey (black-tailed jackrabbit, Lepus californicus; and desert cottontail,
 Sylvilagus audubonii) in the Chihuahuan Desert of New Mexico, USA. We
 evaluated alternative hypotheses for how shrub encroachment could affect
 habitat use and trophic interactions, including i) modifying bottom-up
 processes by reducing herbaceous forage, ii) modifying top-down processes
 by changing canid space use or the landscape of fear experienced by
 lagomorph prey, and iii) altering intraguild interactions between the
 dominant coyote and the intermediate kit fox. We used seven years of
 camera trap data collected across grassland-to-shrubland gradients under
 variable precipitation to test our a priori hypotheses within a
 structural equation modeling framework. Lagomorph prey responded strongly
 to bottom-up pulses during years of high summer precipitation, but only at
 sites with moderate to high shrub cover. This outcome is inconsistent with
 the hypothesis that bottom-up effects should be strongest in grasslands
 because of greater herbaceous food resources. Instead, this interaction
 likely reflects changes in the landscape of fear because perceived
 predation risk in lagomorphs is reduced in shrub-dominated habitats. Shrub
 encroachment did not directly affect predation pressure on lagomorphs by
 changing canid site use intensity. However, site use intensity of both
 canid species was positively associated with jackrabbits, indicating
 additional bottom-up effects. Finally, we detected interactions between
 predators in which coyotes restricted space use of kit foxes, but these
 intraguild interactions also depended on shrub encroachment. Our findings
 demonstrate how environmental change can affect trophic interactions
 beyond traditional top-down and bottom-up processes by altering perceived
 predation risk in prey. These results have implications for understanding
 spatial patterns of herbivory and the feedbacks that reinforce shrubland
 states in drylands worldwide.
description: Data collected using camera traps, line point intercept methods,
 and rain gauges.
description: # Dryland state transitions alter trophic interactions in a predator-prey
 system
 [https://doi.org/10.5061/dryad.2547d7wz8](https://doi.org/10.5061/dryad.2547d7wz8) ## Description of the data and file structure **This repository contains data for the following manuscript:** Wagnon, C. J., B. T. Bestelmeyer, and R. L. Schooley. Dryland state transitions alter trophic interactions in a predator-prey system. The following file is included: **trophic.data** Camera trap and environmental data used for SEM analysis. NA values represent missing data. Variable definitions are as follows: * Site = camera site name * Year = year of camera survey * site.cat = unique sampling site id * cam.days = number of days camera traps were active * CL_ind.dec = number of independent photos for coyote * VM_ind.dec = number of independent photos for kit fox * SA_ind.dec = number of independent photos for desert cottontail * LC_ind.dec = number of independent photos for black-tailed jackrabbit * coy.pa = photographic rate for coyote * kit.pa = photographic rate for kit fox * cot.pa = photographic rate for desert cottontail * jac.pa = photographic rate for black-tailed jackrabbit * shrub = percent shrub cover * precip.t.sum = total summer precipitation in millimeters