Temporal and spatial variation in morphology and distributions of Central Texas lizards

Urbanization has been recognized as an important factor influencing plasticity, evolution, and ecology in populations. However, responses to this novel anthropogenic pressure are taxon-specific and at times difficult to disentangle. A useful approach to elucidating these relationships is utilizing morphology given its influence over animal form and function in the environment. I investigated whether urbanization has caused morphology to change through time and across space in lizards in Central Texas. Utilizing a combination of measuring historical specimens and conducting modern field surveys, I found evidence of morphological variation at both temporal and spatial scales as a response to urbanization. Specifically, limb and toe measurements decreased through time in all five lizard species sampled and were larger on average in urban lizards. I also used modern sampling efforts to record presence-absence data to investigate whether urbanization has altered lizard distributions. I found evidence that distributions have potentially been affected by urban development in three lizard species. The implications of my study include a need for more systematic research on urban morphology that can begin in present day and the need to disentangle the interacting but potentially conflicting effects of plasticity, evolution, and ecology when making conclusions about urban and non-urban populations.