Undergraduate Honors Theses

Thesis Defended

Spring 2018

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Ecology and Evolutionary Biology

First Advisor

Kendi Davies

Second Advisor

Barbara Demmig-Adams

Third Advisor

Daniel Doak

Abstract

Habitat loss and fragmentation is the leading cause of biodiversity loss. Metacommunity theory predicts that habitat fragmentation should reduce food-chain length and food-web complexity. Generalist predators’ diets integrated over time should reflect these changes to food-webs. I investigated how habitat fragmentation affects the abundance and distribution, trophic position, and stable isotopic niche of the generalist predator, the funnel-web spider Atrax sutherlandi. I focused my study at a large-scale, long-term habitat fragmentation experiment, the Wog Wog Habitat Fragmentation Experiment, in southeastern NSW, Australia. I collected A. sutherlandi specimens from pitfall traps and analyzed individuals for the stable isotopes, δ13C and δ15N. I predicted habitat fragmentation would decrease abundance, reduce trophic position, and reduce the breadth of the stable isotopic niche area in populations of A. sutherlandi. However, spiders were significantly more abundant in small fragments, particularly edges of small fragment, when compared to the controlled, continuous forest. Habitat fragmentation did not reduce trophic position (via δ15N) of A. sutherlandi. Individuals in the matrix and fragments were on average 1.6 ‰ and 0.62‰ higher in δ15N, respectively, than individuals in controls. Stable isotopic niche area was largest in the matrix (2.86 ‰2), followed by fragments (1.60 ‰2), and smallest in the continuous forest (1.25‰2). Contrary to predictions from metacommunity theory, habitat fragmentation appeared to increase the trophic position and stable isotopic niche breadth of A. sutherlandi. I speculate that these changes may instead be driven by variation in leaf litter depth or alterations in funnel-web behavior due to habitat fragmentation.

Available for download on Sunday, April 12, 2020

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