Glacial cycles drive rapid divergence of cryptic field vole species

Fletcher, Nicholas K; Acevedo, Pelayo; Herman, Jeremy S; Paupério, Joana; Alves, Paolo C; Searle, Jeremy B

Glacial cycles drive rapid divergence of cryptic field vole species

Resource type

Journal article

Creator (person)

Fletcher, Nicholas K

Acevedo, Pelayo

Herman, Jeremy S

Paupério, Joana

Alves, Paolo C

Searle, Jeremy B

Date published

November 23, 2019

Abstract

Understanding the factors that contribute to the generation of reproductively isolated forms is a fundamental goal of evolutionary biology. Cryptic species are an especially interesting challenge to study in this context since they lack obvious morphological differentiation that provides clues to adaptive divergence that may drive reproductive isolation. Geographical isolation in refugial areas during glacial cycling is known to be important for generating genetically divergent populations, but its role in the origination of new species is still not fully understood and likely to be situation dependent. We combine analysis of 35,434 single-nucleotide polymorphisms (SNPs) with environmental niche modeling (ENM) to investigate genomic and ecological divergence in three cryptic species formerly classified as the field vole (Microtus agrestis). The SNPs demonstrate high genomic divergence (pairwise FST values of 0.45 - 0.72) and little evidence of gene flow among the three field vole cryptic species, and we argue that genetic drift may have been a particularly important mechanism for divergence in the group. The ENM reveals three areas as potential glacial refugia for the cryptic species and differing climatic niches, although with spatial overlap between species pairs. This evidence underscores the role that glacial cycling has in promoting genetic differentiation and reproductive isolation by subdivision into disjunct distributions at glacial maxima in areas relatively close to ice sheets. Future investigation of the intrinsic barriers to gene flow between the field vole cryptic species is required to fully assess the mechanisms that contribute to reproductive isolation. In addition, the Portuguese field vole (M. rozianus) shows a high inbreeding coefficient and a restricted climatic niche, and warrants investigation into its conservation status.

Funder

Funder name	Awards
Universidad de Castillaà¢â‚¬ï¿½La Mancha (UCLM). Grant Number: RYCà¢â‚¬ï¿½2012à¢â‚¬ï¿½11970
Spanish Ministerio de Economàƒa y Competitividad (MINECO)
American Society of Mammalogists' Grantsà¢â‚¬ï¿½inà¢â‚¬ï¿½Aid
European Union's Horizon 2020 Research and Innovation Program. Grant Number: 668981
Society for the Study of Evolution Rosemary Grant