Meeting Abstract
Color polymorphism, in which multiple color patterns co-occur in a population, presents a paradox in mimicry systems with aposematism – if model resemblance is beneficial, then what is the adaptive significance of multiple morphs? Nevertheless, potential explanations for the maintenance of color polymorphism in mimicry systems include frequency-dependent selection, regulation via supergenes, sexual selection, and selection that varies over time and space. One way to test among these hypotheses is to compare mimetic and non-mimetic color traits, which may respond differently to selection. We tested how selection drives spatial patterns of these different types of color traits using the ground snake (Sonora episcopa), which is polymorphic for two mimetic traits (black bands, red stripe) and two non-mimetic traits (black cap, black collar). We analyzed spatial patterns of color traits using 1,240 individuals from 49 populations, conducted population genetic tests for selection using ddRAD sequence data, and modeled linkage relationships among color traits. We found mimetic and non-mimetic traits to be spatially and genetically linked with one another. We also found that both mimetic and non-mimetic traits are under diversifying selection, but the evidence for this selection is much stronger for mimetic traits than for non-mimetic traits. When taken together, our results imply that strong diversifying selection on mimetic traits may maintain polymorphism of both mimetic and non-mimetic color traits through genetic linkage, despite weaker selection on non-mimetic traits. Such findings present a previously-unstudied way in which phenotypic diversity can be maintained in mimicry complexes and have further implications for color pattern diversity across the tree of life.
