Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Ecology & Ecosystem Sciences (EES)

Department

Biological Sciences

First Advisor

Jason J. Kolbe

Abstract

The biological invasion of the brown anole (Anolis sagrei) provides an opportunity to test alternative hypotheses for phenotypic evolution as non-native populations established from multiple native-range sources experience different environmental conditions. In this study, we explored the evolution of Anolis lizard dewlaps, a well-studied communication structure with a remarkable diversity of phenotypes within and among species. Considerable evidence exists showing that the dewlap is a multifaceted trait subject to multiple selective pressures related to the local environmental conditions. We tested adaptive hypotheses for the response to climate and habitat variation as well as non-adaptive hypotheses tracing the genetic history of the invasion. We studied dewlap reflectance, pattern and size in brown anole populations across a portion of its non-native range in Florida and Georgia (USA). Using genome-wide SNP data to estimate genetic ancestry from the native range, we found that variation among introduced populations in dewlap brightness, ultraviolet (UV) reflectance, yellow composition and patterning was best explained by the frequency of west Cuban ancestry, the primary source of non-native populations in southern Florida. Despite the strong imprint of the invasion history on dewlap variation, we also detected significant relationships between aspects of the dewlap and local environmental conditions. Dewlap brightness was correlated with canopy openness and annual mean temperature, and UV reflectance was correlated with canopy openness and annual mean precipitation. These trait-environment correlations support a role for natural selection in shaping dewlap characteristics during the brown anole invasion. By characterizing the evolutionary processes responsible for rapid evolution during the invasion, this study provides insight in how multiple aspects of a morphological structure (i.e., the dewlap) can retain the strong influence of its genetic ancestry while simultaneously responding to different selective pressures. Our study further supports the importance of genetic ancestry and admixture for shaping phenotypes during biological invasions, and reveals that at least some traits in non-native populations can still respond adaptively to local conditions despite the potential constraints of this invasion history.

Available for download on Saturday, August 13, 2022

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