Congruent morphological and genetic differentiation as a signature of range expansion in a fragmented landscape

Abstract

Phenotypic differentiation is often interpreted as a result of local adaptation of individuals to their environment. Here, we investigated the skull morphological differentiation in 11 populations of the white-footed mouse (Peromyscus leucopus). These populations were sampled in an agricultural landscape in the Montérégie region (Québec, Canada), at the northern edge of the distribution of the white-footed mouse. We found a strong pattern of phenotypic differentiation matching the genetic structure across these populations. Landscape fragmentation and the presence of geographic barriers, in particular north–south oriented rivers, contribute to this differentiation and modulate the pattern of rapid ongoing northward range expansion of the white-footed mouse in response to climate warming. We conclude that while large rivers and postglacial recolonization routes have shaped the current pattern of distribution and differentiation of white-footed mouse populations, further local differentiation is occurring, at the scale of the landscape. We posit that the northern expansion of the white-footed mouse is achieved through successive independent founder events in a fragmented landscape at the northern range edge of the species. The phenotypic differentiation we observe is thus a result of a number of mechanisms operating at different spatial and temporal scales.

Effects of parasite and historic driven selection on the diversity and structure of a MHC-II gene in a small mammal species (Peromyscus leucopus) undergoing range expansion

“…With the DRB gene, we still detected two distinct clusters, but surprisingly populations from the East Coast appeared closer to populations from the northern shore of the St Lawrence river and the population from the Great Lakes region, than to populations from the southern shore of the St Lawrence river. Further sub-structure was detected among the populations south of the St Lawrence river, with an effect of the Richelieu river, as previously shown using neutral microsatellite markers (Rogic et al 2013;Marrotte et al 2014) and based on the morphological variation in skull shape (Ledevin and Millien 2013).…”

Climate change and habitat fragmentation drive the occurrence of Borrelia burgdorferi, the agent of Lyme disease, at the northeastern limit of its distribution

“…). Using neutral genetic markers and landmark data from the skull, we detected a strong geographical differentiation of populations of the white‐footed mouse across forest patches within our study area (Ledevin and Millien ; Rogic et al. ).…”

“…). Small forest patches are often surrounded by less suitable habitats which may hinder dispersion and promote genetic and morphological differentiation between isolated populations (Klein and Cameron ; Munshi‐South ; Ledevin and Millien ; Rogic et al. ; R. R. Marrotte, A. Gonzalez, and V. Millien unpublished data).…”

The influence of environmental factors on the morphology of red-backed volesMyodes gapperi(Rodentia, Arvicolinae) in Québec and western Labrador

“…This re‐colonization process may have occurred via a series of successive founder events (e.g. Gracia et al ., ; Schulte et al ., ), a process that may also have played a role in other species occurring in Quebec (Ledevin & Millien, ). These successive founder events would have further structured populations spatially.…”

“…Genetic drift can also influence phenotypic variation, especially in the context of changing environmental conditions. These processes are non‐exclusive, and the morphology of individuals in a population may reflect an interaction between them (Renaud & Michaux, ; Ackermann & Cheverud, ; Ledevin & Millien, ). Identifying the environmental factors that are correlated with variation in size and shape of a structure may help better understand how these factors influence the spatial patterns of morphological variation.…”