Lead in the Red-Zone: A Population Structure Analysis of Red-Backed Salamanders (Plethodon cinereus) with an Unexpected Color Morph in Upstate NY

Abstract

Polymorphisms, such as variations in color, within a species can be a clear visual marker of genetic variation in a population. The eastern red-backed salamander (Plethodon cinereus) appears in two distinct color morphs (lead-back or unstriped, and red-back or striped), which are heritable and vary in frequency among populations. Previous work suggests that variation in P. cinereus color morph frequencies correlates with changes in elevation and climate, but these correlations are not consistent across this salamander’s range. On Long Island, NY, a gradient in color morph frequencies occurs along the environmental gradient of the island. Western populations are entirely striped and eastern populations entirely unstriped; these populations are also genetically distinct. Interestingly, in the Catskill Mts. of upstate NY, entirely striped populations occur in close proximity to polymorphic populations. Starting in spring 2021, we sampled 11 populations of P. cinereus in Schoharie County, NY. We use RAD-sequencing to describe the genetic variation of the sampled salamander populations and test whether morph frequencies, elevation, or climate affected population connectivity. As there is still no clear consensus regarding why P. cinereus color morphs persist or why their frequencies vary among populations, this research may shed further light on this fascinating natural phenomenon. Also, as the protocol of RAD-sequencing for genetic analysis becomes the field standard, this research may serve as a comparable study for future work studying population connectivity in P. cinereus. Although P. cinereus is both abundant and ubiquitous, the results from this research are applicable to more vulnerable amphibians which may be impacted more by climate change and habitat loss.