Environmentally-associated color divergence does not coincide with population structure across Lesser Antillean anoles

Species distributed across heterogeneous environments may undergo local
adaptation, which can be limited by the homogenizing effects of gene flow.
Lesser Antillean anoles exhibit dorsal color variation associated with
dramatic shifts in environment across small spatial scales, providing an
excellent system for studying the maintenance of local adaptation despite
ongoing gene flow. The 1995 Soufriere Hills eruption on Montserrat
provides an opportunity to understand how natural disasters may influence
evolution of insular species. Thus, our study had two main objectives.
First, we collected genetic, phenotypic, and environmental data to
investigate whether environmentally-associated dorsal coloration reflects
underlying population structure in three species of Lesser Antillean
anoles. Second, we examined the short-term evolutionary consequences of
volcanism by comparing pre- and post-eruption samples of Anolis lividus
using multi-locus sequence data. We found all three species exhibited
genetic isolation- by-distance but not isolation-by-environment.
Furthermore, phenotypic differences within each species were not predicted
by genetic distances, suggesting gene flow across color morphs. We
confirmed the repopulation of A. lividus in the impacted area and found
genetic diversity equivalent to pre-eruption sampling. Our findings
contribute to our understanding of local adaptation in spatially
small-scale systems and the impact of catastrophic natural disasters on
population structure.