Dryland state transitions, trophic interactions, and the restoration of a keystone species

Wagnon, Casey John

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https://hdl.handle.net/2142/120215 Copy

Description

Title

Dryland state transitions, trophic interactions, and the restoration of a keystone species

Author(s)

Wagnon, Casey John

Issue Date

2023-03-16

Director of Research (if dissertation) or Advisor (if thesis)

Schooley , Robert L

Doctoral Committee Chair(s)

Miller, James R

Committee Member(s)

• Benson, Thomas J
• Cosentino, Bradley J

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Drylands
• shrub encroachment
• habitat restoration
• trophic interactions
• landscape of fear
• animal personality
• keystone species
• structural equation modeling
• lagomorphs
• canids
• Chihuahuan Desert

Abstract

Shrub encroachment is a global driver of ecosystem change impacting grass-dominated drylands, with consequences for trophic interactions. Such state transitions have prompted shrub removal efforts in attempts to reverse the process and restore encroached grasslands. However, we lack adequate understanding of how trophic food webs respond to shrub encroachment or how habitat restoration actions impact animal behavior, including shrub removal. My research examined how shrub encroachment and grassland restoration efforts in the Chihuahuan Desert of New Mexico shapes the trophic and behavioral ecology of mammals. I first evaluated how shrub encroachment affects trophic interactions and the landscape of fear in a canid-lagomorph system. Lagomorph prey responded strongly to bottom-up pulses during years of high summer precipitation but only on 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 pattern is consistent with changes in the landscape of fear because perceived predation risk in lagomorphs is reduced in shrub-dominated habitats. I then examined the behavioral response of a keystone rodent of grasslands, Dipodomys spectabilis, to extensive shrub removal efforts by comparing personality traits and movement behavior between restoration and remnant habitats. Personality traits were present in D. spectabilis but did not strongly differ between environments. Notably, D. spectabilis exhibited personality-dependent movement through artificial shrubs in a movement experiment, suggesting a mechanistic pathway affecting colonization dynamics of shrub removal sites. My research reveals the varied and complex ways that wildlife populations may respond to ecosystem change in drylands. Future research should consider the landscape of fear and animal personality when evaluating wildlife responses to global change drivers and habitat restoration.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Casey Wagnon

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