Theses and Dissertations from DePaul University

Date of Award

Spring 2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

College

College of Science and Health

First Advisor

Noé de la Sancha

Abstract

Habitat loss and fragmentation are major drivers of biodiversity decline and can alter the physiological condition of wildlife through changes in habitat quality, resource availability, and community composition. The Atlantic Forest of South America is one of the world’s most threatened biodiversity hotspots. This study examined relationships among biodiversity, landscape structure, and chronic stress in nonvolant small mammals within the Reserva Natural Tapytá in eastern Paraguay using hair glucocorticoid concentrations as indicators of long-term physiological stress. Small mammals were sampled from forest fragments representing multiple patch sizes between 2023 and 2025. Hair cortisol and corticosterone concentrations were quantified using enzyme immunoassays, biodiversity was characterized using taxonomic, functional, and phylogenetic metrics, and landscape structure was quantified across multiple spatial scales. Linear mixed-effects models and nonparametric analyses were used to evaluate relationships among glucocorticoids, biodiversity, landscape structure, and biological variables. Hormone concentrations differed significantly among species, taxonomic groups, body mass classes, body condition categories, and year of capture. Rodents generally exhibited higher glucocorticoid concentrations than marsupials, and species identity emerged as one of the strongest predictors of variation in hormone concentrations. Phylogenetic diversity, particularly mean pairwise phylogenetic distance (PDmpd), was consistently associated with lower cortisol and corticosterone concentrations. Taxonomic diversity metrics incorporating species abundance also exhibited negative relationships with corticosterone concentrations. Landscape structure primarily influenced cortisol concentrations, with forest cover, core area, and edge density emerging as important predictors at local spatial scales. These findings demonstrate that physiological responses to habitat fragmentation are influenced by interactions among individual characteristics, biodiversity, and landscape structure. This study highlights the value of integrating conservation physiology, biodiversity metrics, and landscape ecology to better understand wildlife responses to environmental change in fragmented tropical forests.

Download

Share

COinS