Differentiation of tundra/taiga and boreal coniferous forest wolves: genetics, coat colour and association with migratory caribou

Abstract

The grey wolf has one of the largest historic distributions of any terrestrial mammal and can disperse over great distances across imposing topographic barriers. As a result, geographical distance and physical obstacles to dispersal may not be consequential factors in the evolutionary divergence of wolf populations. However, recent studies suggest ecological features can constrain gene flow. We tested whether wolf-prey associations in uninterrupted tundra and forested regions of Canada explained differences in migratory behaviour, genetics, and coat colour of wolves. Satellite-telemetry data demonstrated that tundra wolves (n = 19) migrate annually with caribou (« = 19) from denning areas in the tundra to wintering areas south of the treeline. In contrast, nearby boreal coniferous forest wolves are territorial and associated year round with resident prey. Spatially explicit analysis of 14 autosomal microsatellite loci (n = 404 individuals) found two genetic clusters corresponding to tundra vs. boreal coniferous forest wolves. A sex bias in gene flow was inferred based on higher levels of mtDNA divergence (Fg^ = 0.282, 0.028 and 0.033; P < 0.0001 for mitochondrial, nuclear autosomal and Y-chromosome markers, respectively). Phenotypic differentiation was substantial as 93% of wolves from tundra populations exhibited light colouration whereas only 38% of boreal coniferous forest wolves did (y} = 64.52, P < 0.0001). The sharp boundary representing this discontinuity was the southern limit of the caribou migration. These findings show that substantial genetic and phenotypic differentiation in highly mobile mammals can be caused by prey-habitat specialization rather than distance or topographic barriers. The presence of a distinct wolf ecotype in the tundra of North America highlights the need to preserve migratory populations.

Using genetic methods to investigate dispersal in two badger (Meles meles) populations with different ecological characteristics

“…There have also been a number of recent landscape genetic studies that have shown that dispersal in carnivore species can be habitat specific, that is, individuals have a tendency to disperse preferentially into habitat similar to their natal one (Pilot et al, 2006;Carmichael et al, 2007;Musiani et al, 2007). These studies found a good concordance between geographical boundaries of genetic clusters and ecological factors such as climate and habitat types, as well as diet composition and distribution of prey.…”

Concordant mitochondrial and microsatellite DNA structuring between Polish lowland and Carpathian Mountain wolves

“…Associations between environmental factors (habitat type, climate, prey abundance) and genetic variants might have resulted in the development of wolf ecotypes adapted to different habitats (e.g. Carmichael et al Conserv Genet (2013) 14:573-588 583 2001; Musiani et al 2007;Muñoz-Fuentes et al 2009). This is consistent with the findings that (1) ecological factors (habitat, prey, climate) appear to explain much of the spatial variation in wolf genetic diversity in east-central Europe (Pilot et al 2006), and that (2) wolves from three genetically distinct populations in Poland show significant differences in prey composition and prey preferences (Jedrzejewski et al 2012).…”

Ecological opportunities and specializations shaped genetic divergence in a highly mobile marine top predator

“…Preferential dispersal towards a habitat similar to one of juvenile life [16] can generate and maintain evolutionary divergence in highly mobile species. While this process may be 'imprinted' in turtles or fishes [17], social learning of foraging techniques for particular prey or habitat may influence dispersal in species having long-term bonds between mothers and calves [4,15]. Individuals may therefore have higher foraging success in familiar habitats where they can use learned hunting techniques, which might enhance their fitness.…”

“…In the absence of geographical barriers to gene flow, habitat and/or prey preferences among groups of individuals can lead to genetic and morphological differentiation. For example, top predators inhabiting neighbouring areas, such as grey wolves in boreal coniferous forest and tundra/taiga, that are known to specialize on different prey, can be genetically and phenotypically differentiated [4]. Other examples include Galapagos sea lions from two distinct rookeries foraging in benthic and pelagic habitats, sympatric populations of killer whales specializing on fish or marine mammals in the North-east Pacific and sympatric generalist and specialist killer whales in the North-east Atlantic (NEA) [5][6][7].…”