Abstract
Wide-ranging animals, including migratory species, are significantly threatened by the effects of habitat fragmentation and habitat loss. In the case of terrestrial mammals, this results in nearly a quarter of species being at risk of extinction. Caribou are one such example of a wide-ranging, migratory, terrestrial, and endangered mammal. In populations of caribou, the proportion of individuals considered as “migrants” can vary dramatically. There is therefore a possibility that, under the condition that migratory behavior is genetically determined, those individuals or populations that are migratory will be further impacted by humans, and this impact could result in the permanent loss of the migratory trait in some populations. However, genetic determination of migration has not previously been studied in an endangered terrestrial mammal. We examined migratory behavior of 139 GPS-collared endangered caribou in western North America and carried out genomic scans for the same individuals. Here we determine a genetic subdivision of caribou into a Northern and a Southern genetic cluster. We also detect >50 SNPs associated with migratory behavior, which are in genes with hypothesized roles in determining migration in other organisms. Furthermore, we determine that propensity to migrate depends upon the proportion of ancestry in individual caribou, and thus on the evolutionary history of its migratory and sedentary subspecies. If, as we report, migratory behavior is influenced by genes, caribou could be further impacted by the loss of the migratory trait in some isolated populations already at low numbers. Our results indicating an ancestral genetic component also suggest that the migratory trait and their associated genetic mutations could not be easily re-established when lost in a population.
Highlights
Migration, the directional movement from one location to another and back, is observed in numerous species of vertebrates [1], including approximately 36% of marine mammals and about 1% of terrestrial mammals [2]
The use of global positioning system (GPS) transmitters permitted the detection of migratory or sedentary movements of 139 endangered caribou
Propensity to migrate depended upon the proportion of Northern or Southern ancestry in individual caribou, and on the evolutionary history of its migratory and sedentary subspecies dating back to the last glaciation
Summary
The directional movement from one location to another and back, is observed in numerous species of vertebrates [1], including approximately 36% of marine mammals and about 1% of terrestrial mammals [2]. The bases of animal migration, and the bases of its suite of characteristics (e.g. tendency to migrate or not, timing, direction, and distance), remain largely unknown. Migratory behavior could be learned or dependent on physiological and nutritional conditions [13,14,15], or even triggered by environmental ones [12,16]. Migratory behavior could be influenced by the interaction of several of the aforementioned components [12,16,17]
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