A population on the edge: genetic diversity and population structure of the world's northernmost harbour seals (Phoca vitulina)

Abstract

It is crucial to examine the genetic diversity and structure of small, isolated populations, especially those at the edge of their distribution range, because they are vulnerable to stochastic processes if genetic diversity is low and the isolation level is high, and because such populations provide insight into the consequences of population declines in a broader conservation context. The harbour seal (Phoca vitulina) population in Svalbard is the world's northernmost P. vitulina population. Nothing is known about the genetic diversity, distinctiveness, or origin of this small, marginalized mammalian population. Thus, the present study investigated its genetic status in the context of nearby P. vitulina in Iceland, south‐east Greenland, and northern Norway: this species is depleted/threatened in all of these regions. A total of 174 samples distributed between the four locations were analysed using 15 polymorphic microsatellites and variation in the displacement loop region (D‐loop). Each of the four locations was a genetically distinct population. The Svalbard population was highly genetically distinct, had reduced genetic diversity, received limited gene flow, had a rather low effective population size, and showed an indication of having experienced a bottleneck resulting from a recent population decline. The significant heterozygote excess observed in the Svalbard sample might be attributed to the low effective population size, which could initiate future population inbreeding effects. This phenomenon has not been reported earlier from other P. vitulina populations, but if the Svalbard population is experiencing inbreeding, this could reduce its resilience to climate change, disease outbreaks, or other perturbations. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 420–439.

The Limits of Dispersal: Fine Scale Spatial Genetic Structure in Australian Sea Lions

“…Differentiation between South Australian and Western Australian colonies is not surprising considering the distance (>2200 km) between these two regions. However in comparison to other pinniped studies conducted at similar or larger spatial scales the F ST values reported here between these two regions were higher (Hoelzel et al, 2001;Palo et al, 2001;Coltman et al, 2007;Graves et al, 2009;Andersen et al, 2011;Feijoo et al, 2011). Strong genetic partitioning between South Australian and West Australian colonies is also evident with mtDNA data (significant pairwise ST values ranged from 0.83 to 0.94, Campbell et al, 2008).…”

Tipping Elements in the Arctic Marine Ecosystem

“…There is already evidence that populations of key Arctic species dependent on ice are under stress, as reflected in declining growth, condition, and reproductive output, particularly for the polar bears and some of the seal species most dependent on ice (Renaud et al 2008;Wassmann et al 2011;Andersen et al 2011). As their populations decline with ice loss, they are expected to hybridize with closely related species, a process eventually leading to the loss of these species (Kelly et al 2010).…”

Harbour seal Phoca vitulina movement patterns in the high-Arctic archipelago of Svalbard, Norway

“…This small, isolated population of ca. 2000 animals (Merkel et al 2013) has low genetic diversity (Andersen et al 2011); it is Red-listed in Norway and hence protected from harvesting. The haul-out behaviour of this population has been studied intensively (Reder et al 2003), and concomittantly with the current stud (see Hamilton et al 2014), but the at-sea behaviour of adult harbor seals re mains largely undocumented.…”