Patterns of Genetic And Epigenetic Diversity Across A Range Expansion in The White-Footed Mouse (Peromyscus Leucopus)

Populations at the leading front of a range expansion must rapidly adapt to novel conditions. Increased epigenetic diversity has been hypothesized to facilitate adaptation and population persistence via non-genetic phenotypic variation, especially if there is reduced genetic diversity when populations expand (i.e., epigenetic diversity compensates for low genetic diversity). In this study, we use the spatial distribution of genetic and epigenetic diversity to test this hypothesis in populations of the white-footed mouse (Peromyscus leucopus) sampled across a purported recent range expansion gradient. We found mixed support for the epigenetic compensation hypothesis and a lack of support for expectations for expansion populations of mice at the range edge, which likely reflects a complex history of expansion in white-footed mice in the Upper Peninsula of Michigan. Specifically, epigenetic diversity was not increased in the population at the purported edge of the range expansion in comparison to the other expansion populations. However, input from an additional ancestral source populations may have increased genetic diversity at this range edge population, counteracting the expected genetic consequences of expansion, as well as reducing the benefit of increased epigenetic diversity at the range edge. Future work will expand the focal populations to include expansion areas with a single founding lineage to test for the robustness of a general trend that supports the hypothesized compensation of reduced genetic diversity by epigenetic variation observed in the expansion population that was founded from a single historical source.