Date of Award

12-2025

Document Type

Thesis

Degree Name

Master of Science in Biology

Department

Biology

First Reader/Committee Chair

Horner, Angela

Abstract

With increasing urbanization due to rising human populations, organisms may be forced to adapt rapidly to changing environments. Urbanization is replacing natural surfaces with more impervious substrates which can result in morphological changes affecting organismal locomotion, then also impact fitness. This study compares urban and natural habitat impact on Western Fence Lizards (Sceloporus occidentalis) and their adaptations in such settings. We captured lizards from three locations in inland Southern California with both urbanized and natural habitats in order to compare the morphological differences between lizards, and then measured their performance to determine the possible impacts from their morphology. We hypothesized that lizards will be found more often on human-made substrates in urban habitats, showing a shift in substrate use. We also hypothesized that limb and toe lengths in Western Fence Lizards would be correlated with locomotion ability and predicted that urban lizards would have shorter limb and toe lengths (based on prior work), and thus run slower when compared to lizards living in natural habitats. We measured snout-vent-length, tail length, forearm, hindlimb, plantar, and toe length, components that have been shown to affect the movement of lizards. We measured the speed and stride characteristics of each lizard by filming them running across a trackway. We compared speed, stride length, stride frequency, and duty factor to the lizard morphology data. Results show that tail length, and toe length are shorter in urban lizards compared to natural lizards. Other trait measurements also had significant results, but varied by location, with urban lizards in Claremont showing larger morphological traits, while those in Redlands exhibited smaller ones compared to their natural counterparts. Although there were changes to morphology, there were no differences in performance and stride attributes between urban and natural lizards. The reasons for these results remain unclear, as locomotor speed in animals can be influenced by many factors, and further historical context of each location; as well as testing additional performance traits beyond running speed may be necessary to fully interpret these patterns. This study provided valuable insight into the complex relationship between morphology and performance in Western Fence Lizards. Our findings highlight the need for long-term, multi-site studies to better understand how urbanization shapes organismal biology.

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