Genome-wide set of SNPs reveals evidence for two glacial refugia and admixture from postglacial recolonization in an alpine ungulate.

Past glaciation events have played a major role in shaping the genetic diversity and distribution of wild sheep in North America. The advancement of glaciers can isolate populations in ice-free refugia, where they can survive until the recession of ice sheets. The major Beringian refugium is thought to have held thinhorn sheep (Ovis dalli) populations during times of glacial advance. While isolation in the major refugium can account for much of the genetic and morphological diversity seen in extant thinhorn sheep populations, mounting evidence suggests the persistence of populations in smaller minor refugia. We investigated the refugial origins of thinhorn sheep using ~10 000 SNPs obtained via a cross-species application of the domestic sheep ovine HD BeadChip to genotype 52 thinhorn sheep and five bighorn sheep (O. canadensis) samples. Phylogenetic inference revealed a distinct lineage of thinhorn sheep inhabiting British Columbia, which is consistent with the survival of a group of thinhorn sheep in a minor refugium separate from the Beringian refugium. Isolation in separate glacial refugia probably mediated the evolution of the two thinhorn sheep subspecies, the white Dall's sheep (O. d. dalli), which persisted in Beringia, and the dark Stone's sheep (O. d. stonei), which utilized the minor refugium. We also found the first genetic evidence for admixture between sheep from different glacial refugia in south-central Yukon as a consequence of post glacial expansion and recolonization. These results show that glaciation events can have a major role in the evolution of species inhabiting previously glaciated habitats and the need to look beyond established refugia when examining the evolutionary history of such species.

Seasonal effects of Pacific-based climate on recruitment in a predator-limited large herbivore.

1. Climate is an important factor influencing the population dynamics of large herbivores operating directly on individuals or through its effect on forage characteristics. However, the seasonal effect of climate may differ between forage- and predator-limited populations because of a climatic influence on predation rates. The influence of climate on predator-limited large herbivores is less well known than on forage-limited populations. Further, the effect of Pacific-based climate on large herbivore populations has been rarely assessed. 2. We investigated the effect of the Pacific Decadal Oscillation (PDO), across different seasons, on recruitment in 10 populations (herds) of mountain-dwelling caribou Rangifer tarandus caribou L. in the Yukon Territory, Canada. These low-density populations occur in highly seasonal environments and are considered predator-limited with high neonatal calf mortality. Hence, in most years females do not spend resources through lactational support during the summer and resource intake is devoted to self-maintenance. We predicted that climate affecting environmental conditions at calving would have a strong effect on recruitment via its influence on predation rates. We also predicted that climatic conditions prior to conception could have an effect on recruitment through its influence on female fecundity. We modelled recruitment (n = 165) by seasonal PDO values using generalized linear mixed-effects models with herd-varying coefficients. 3. We found that recruitment variability was best explained by variation in winter climate (beta = 0.110, SE = 0.007) prior to birth (in utero) and May climate (beta = 0.013, SE = 0.006) at calving. There was little support for a pre-conception climate effect influencing female body condition and hence fecundity. These results confirm that recruitment in these populations is limited by predation and that forage-limitation is not a significant factor in their population dynamics. There was considerable variability in herd-specific relationships between the PDO and recruitment. Incorporating herd-specific characteristics, such as variable predator densities or terrain characteristics within a herd range, may shed greater light on the complex relationship between climate and ungulate population dynamics.

The geography of conflict between elk and agricultural values in the Cypress Hills, Canada.

Complex ecological issues like depredation and its management are determined by multiple factors acting at more than one scale and are interlinked with complex human social and economic behaviour. Depredation by wild herbivores can be a major obstacle to agricultural community support for wildlife conservation. For three decades, crop and fence damage, competition with livestock for native rangeland and tame pasture, and depredation of stored feed by elk (Cervus elaphus canadensis) have been the cause of conflict with agricultural producers in the Cypress Hills, Alberta and Saskatchewan. Tolerance of elk presence on private lands is low because few benefits accrue to private landowners; rather they largely perceive elk as a public resource produced at their expense. Government management actions have focused on abatement inputs (e.g., population reduction; fencing) and compensation, but incentives to alter land use patterns (crop choice and location) in response to damages have not been considered. Nor has there been information on spatial structure of the elk population that would allow targeted management actions instead of attempting to manage the entire population. In this study we analysed the spatial structure of the Cypress Hills elk population, the distribution of the elk harvest in relation to agricultural conflicts, developed models of the spatial patterns of conflict fields, and evaluated compensation patterns for damage by wild herbivores. We propose modifications to current abatement and compensation programs and discuss alternative approaches involving changes to agricultural land use patterns that may reduce the intensity of conflicts with elk, and increase the acceptance capacity of landowners.