Abstract
Introductions of invasive species to new environments often result in
rapid rates of trait evolution. While in some cases these evolutionary
transitions are adaptive and driven by natural selection, they can also
result from patterns of genetic and phenotypic variation associated with
the invasion history. Here, we examined the brown anole (Anolis
sagrei ), a widespread invasive lizard for which genetic data have
helped trace the sources of non-native populations. We focused on the
dewlap, a complex signaling trait known to be subject to multiple
selective pressures. We measured dewlap reflectance, pattern, and size
in 30 non-native populations across the southeastern United States. As
well, we quantified environmental variables known to influence dewlap
signal effectiveness, such as canopy openness. Further, we used
genome-wide data to estimate genetic ancestry, perform association
mapping, and test for signatures of selection. We found that
among-population variation in dewlap characteristics was best explained
by genetic ancestry. This result was supported by genome-wide
association mapping, which identified several ancestry-specific loci
associated with dewlap traits. Despite the strong imprint of this aspect
of the invasion history on dewlap variation, we also detected
significant relationships between dewlap traits and local environmental
conditions. However, we found limited evidence that dewlap-associated
genetic variants have been subject to selection. Our study emphasizes
the importance of genetic ancestry and admixture in shaping phenotypes
during biological invasion, while leaving the role of selection
unresolved, likely due to the polygenic genetic architecture of dewlaps
and selection acting on many genes of small effect.