Pulses of movement across the sea ice: population connectivity and temporal genetic structure in the arctic fox

Abstract

Lemmings are involved in several important functions in the Arctic ecosystem. The Arctic fox (Vulpes lagopus) can be divided into two discrete ecotypes: "lemming foxes" and "coastal foxes". Crashes in lemming abundance can result in pulses of "lemming fox" movement across the Arctic sea ice and immigration into coastal habitats in search for food. These pulses can influence the genetic structure of the receiving population. We have tested the impact of immigration on the genetic structure of the "coastal fox" population in Svalbard by recording microsatellite variation in seven loci for 162 Arctic foxes sampled during the summer and winter over a 5-year period. Genetic heterogeneity and temporal genetic shifts, as inferred by STRUCTURE simulations and deviations from Hardy-Weinberg proportions, respectively, were recorded. Maximum likelihood estimates of movement as well as STRUCTURE simulations suggested that both immigration and genetic mixture are higher in Svalbard than in the neighbouring "lemming fox" populations. The STRUCTURE simulations and AMOVA revealed there are differences in genetic composition of the population between summer and winter seasons, indicating that immigrants are not present in the reproductive portion of the Svalbard population. Based on these results, we conclude that Arctic fox population structure varies with time and is influenced by immigration from neighbouring populations. The lemming cycle is likely an important factor shaping Arctic fox movement across sea ice and the subsequent population genetic structure, but is also likely to influence local adaptation to the coastal habitat and the prevalence of diseases.

Spatiotemporal distribution of rabies in Arctic foxes in Greenland

“…These are significantly longer intervals than those observed in both North America and Svalbard where cyclicity of 3-5 years has been reported (Tabel et al 1974;Nadin-Davis et al 2008) but comparable with the 6-10 years suggested by Mørk and Prestrud (2004) for arctic populations in general. The link between the cyclic occurrence of rabies outbreaks in Arctic fox populations reported here and in related studies is often reported as being correlated to fox population density, relying in part on cyclic variations in prey abundance, e.g., rodents (Ballard et al 2001;Dalén et al 2005;Norén et al 2011b). When Arctic fox populations peak in numbers, the likelihood of encounters between individuals increases once the foxes disperse (Tabel et al 1974;Mørk and Prestrud 2004;Mørk et al 2011).…”

Age-dependent genetic structure of arctic foxes in Svalbard

“…Immigration might also have contributed somewhat to the observed linkage disequilibrium. Indeed, Noren et al (2011) recently presented genetic evidence for immigration into the Svalbard population following a lemming population crash, and they identified two individuals as likely originating from Siberia.…”

Loss of connectivity among island-dwelling Peary caribou following sea ice decline

“…Its loss and thinning could impede movement and induce a cascade of unprecedented effects [6]. For Arctic fox (Vulpes lagopus), ice allows for long-distance movements, giving rise to a genetically homogeneous population that spans the North American and Svalbard archipelagos [8]. For wolves (Canis lupus), it mediates movement among islands and the mainland, allowing for recolonization of extirpated populations [9].…”