Genetic diversity, structure and gene flow of migratory barren-ground caribou (Rangifer tarandus groenlandicus) in Canada

Abstract

Migratory barren-ground caribou (Rangifer tarandus groenlandicus) provide an opportunity to examine the genetic population structure of a migratory large mammal whose movements and distribution, in some instances, have not been heavily influenced by human activities that result in habitat loss or fragmentation. These caribou have likely reached large effective population sizes since their rapid radiation during the early Holocene despite cyclic changes in abundance. Migratory barren-ground caribou are managed as discrete subpopulations. We investigated genetic variation among those subpopulations to determine the patterns of genetic diversity within and among them, and the implications for long-term persistence of caribou. We identified three distinct genetic clusters across the Canadian arctic tundra: the first cluster consisted of all fully-continental migratory barren-ground subpopulations; the second cluster was the Dolphin and Union caribou; and the third cluster was caribou from Southampton Island. The Southampton Island caribou are especially genetically distinct from the other barren-ground type caribou. Gene flow among subpopulations varied across the range. Occasional gene flow across the sea-ice is likely the reason for high levels of genetic variation in the Dolphin and Union subpopulation, which experienced very low numbers in the past. These results suggest that for most migratory caribou subpopulations, connectivity among subpopulations plays an important role in maintaining natural genetic diversity. Our analyses provide insight into the levels of microsatellite genetic diversity and patterns of gene flow that may be common to large subpopulations that historically had a continuous distribution across a large continental range. These data can also be used as a benchmark to compare the effects of habitat fragmentation and bottlenecks on other large caribou populations.

The Curious Case of King William Island, Nunavut: An Island Overlooked in Caribou Research

“…KWI is often omitted from delineations of major barren-ground herd ranges (Calef, 1979;Calef and Heard, 1981;Ferguson and Gauthier, 1992;Heard and Stenhouse, 1992;GNWT, 2006GNWT, , 2011Dumond, 2007;Nesbitt and Adamczewski, 2009;Vors and Boyce, 2009), or the island is not clearly represented (GN, 2007a;Gunn et al, 2011;CARMA, 2013b Nagy et al, 2011;Nagy and Campbell, 2012;McFarlane et al, 2016) (Figs. 2, 3), although this depiction of herd range extending onto KWI tends to be a result of statistical interpolation of satellite collar tracking data.…”

Interchange and Overlap Among Four Adjacent Arctic Caribou Herds

“…Boulet et al (2007) reported that microsatellite markers and space use data did not show sex differences in gene flow among caribou herds. Other genetic evidence suggested that male dispersal may be more frequent than female dispersal (McFarlane et al 2016).…”

Continental synchrony and local responses: Climatic effects on spatiotemporal patterns of calving in a social ungulate

“…The local specificity of these relationships is an important aspect to consider when generalizing across caribou populations. Although there is some overlap among herds, particularly in the winter months when the animals are most dispersed and movement rates are the lowest, summering ranges and migration pathways tend to be distinct for most herds, and the weather conditions and biotic environments that they experience can be similarly unique, promoting local adaptations as suggested by the high levels of genetic variations in barren-ground caribou populations (McFarlane et al, 2016). In other words, each herd may be adapted to specific local conditions and therefore may have specific optimal conditions, such that the absolute values of such conditions may matter less than deviations from local norms.…”