SICB 2018: Unraveling Natural and Human-Mediated Founder Events in Anolis carolinensis

Photo by Andrea Westmoreland

Human-mediated range expansion is rapidly forming novel populations of anoles. The ancestry of these new populations typically traces back to a handful of individuals, and with repeated invasions the genetic history can be complex. These scenarios may be common in non-native populations of Anolis carolinensis, but what does the genetic history look like in such a system? In Sozos Michaelides’ talk at SICB 2018, he discussed his recently published findings.

Michaelides et al., 2017 tackled the question by inferring colonization history using mitochondrial haplotypes from Hawaiian Islands (Oahu, Hawaii, Maui, and Lanai) and some western Pacific islands (Guam, Palau, Saipan, Yap, and Rota). After genotyping 576 anoles, population genetic diversity and differentiation was assessed between native and non-native ranges. Results indicated geographically disparate haplotypes were identical (Hawaii to Brownsville, Texas), demonstrating that source populations may be from Texas or Louisiana. And a minimum of two introductions to Hawaii and Guam were uncovered, with subsequent within-population stepping-stone model colonization.

Overall, lower genetic diversity was found in non-native island populations as distance increased from the southeastern United States source population, and between the two archipelagos, genetic differentiation was high. Persistence of these non-native populations is not guaranteed because they are isolated, small in population size, and low in genetic diversity. It will be interesting to study the adaptive response of these introduced populations to stochastic climatic events!