Phenotypic Responses to Invasion in the Brown Anole (Anolis sagrei)

Invasive species often encounter climatic conditions that differ significantly from those of their native range. These environmental shifts may trigger phenotypic responses, resulting through some combination of adaptation and plasticity, that enable the invader to persist under novel thermal regimes. In this dissertation, I examine phenotypic changes in a tropical lizard that has successful invaded a cooler temperate climate, specifically examining traits that may promote survival and reproduction in their new range. First, I examined physiological traits, as I predicted greater cold tolerance would be necessary to survival in the invasive range. I found that invasive populations tolerated lower temperatures, exhibited greater maximum sprint speeds, and had higher metabolic rates than native populations. Next, I examined how life-history traits may change in the invasive range in order to facilitate reproduction under shorter breeding and growing seasons. I found that compared to native females, invasive females had shorter interlaying intervals and produced eggs that hatched more quickly. Once I quantified changes physiological and life-history traits that may have aided in successful establishment, I executed a common garden study to determine whether changes were the result of adaptation or plasticity. I found that differences in critical thermal minimum, metabolic rate, interlaying interval, and incubation period were maintained in lab-reared offspring, while measures of sprint speed converged. My results provide evidence that life history and physiology can evolve rapidly during invasion. These findings are useful to understanding contemporary evolution, and also provide valuable insight on how species respond to environmental shifts, both during invasions and as a result of climate change.