Dryland state transitions alter trophic interactions in a predator-prey system
Data files
Sep 20, 2024 version files 12.74 KB
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README.md
1.27 KB
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trophic.data.csv
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Abstract
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.
README: Dryland state transitions alter trophic interactions in a predator-prey system
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
Methods
Data collected using camera traps, line point intercept methods, and rain gauges.