Genetic diversity in a moulting colony of southern elephant seals in comparison with breeding colonies

Abstract

Southern elephant seals Mirounga leonina migrate seasonally between pelagic foraging areas in the Southern Ocean and breeding and moulting sites on subantarctic islands. Here we characterized genetic diversity of the elephant seal moulting colony from King George Island (KGI), South Shetlands Archipelago, in comparison with breeding colonies described in earlier studies. Although KGI serves as a breeding site, the numbers of elephant seals are up to 3 times higher during the moulting season, suggesting post-breeding immigration from other sites, or that large numbers of individuals skip the breeding season every year. High haplotype diversity and a high percentage of shared haplotypes is consistent with the hypothesis of immigration from other South Atlantic colonies, which is also supported by satellite tracking data from earlier studies.Estimates of effective population size at both mtDNA and microsatellite loci were unexpectedly high compared with the census size of the KGI colony, suggesting that they were elevated due to the presence of immigrants. However, we detected few immigrants and no genetic structure in the KGI colony, which could result from the genetic similarity between KGI and other breeding colonies from the South Atlantic, but could also be an effect of an insufficient sampling scheme. These results show the need for genetic monitoring of southern elephant seal colonies throughout their annual cycle to better understand the range of their seasonal movements and patterns of gene flow. The southern elephant seal serves as a model to study links between spatio-temporal environmental variability, population dynamics, and individual movements, physiology and reproductive behavior. Understanding the patterns of dispersal and gene flow in this species is essential to adequately address these general questions.

Movements of southern elephant seals (Mirounga leonina) from Davis Base, Antarctica: combining population genetics and tracking data

“…Previous studies have shown lower genetic diversity in the Península Valdés and Macquarie Island breeding stocks in both mtDNA and microsatellites (Slade et al 1998;Fabiani 2002;Chauke 2008), whereas the study by Hoelzel et al (1993) investigated only mtDNA. In contrast, genetic diversity was higher within the South Georgia stock (South Georgia, Elephant Island, Sea Lion Island, and Falkland Islands seals), and the Kerguelen and Heard Island stock (Heard Island and Marion Island seals), as seen from mitochondrial studies (Hoelzel et al 1993) and other studies that investigated genetic diversity in both mtDNA and microsatellites (Slade et al 1998;Chauke 2008;Bogdanowicz et al 2013). Evidence of sex-biased dispersal was found in previous studies where male-biased gene flow and male dispersal occurred more than in females (Slade et al 1998;Fabiani 2002;Chauke 2008;Bogdanowicz et al 2013;Corrigan et al 2016).…”

“…The genetic structure and genetic diversity of the breeding colonies of SES have been investigated previously using mitochondrial DNA (mtDNA) and microsatellites (Hoelzel et al 1993;Slade et al 1998;Fabiani 2002;Chauke 2008;Bogdanowicz et al 2013). Previous studies have shown lower genetic diversity in the Península Valdés and Macquarie Island breeding stocks in both mtDNA and microsatellites (Slade et al 1998;Fabiani 2002;Chauke 2008), whereas the study by Hoelzel et al (1993) investigated only mtDNA.…”

Dispersal of southern elephant seals (Mirounga leonina) from Davis Base, Antarctica: Combining population genetics and tracking data

“…We collected a total of 201 additional sequences of the mitochondrial control region from GenBank (Hoelzel et al 1993; Slade et al 1998; Fabiani 2002; Chauke 2008; Curtis et al 2009; Bogdanowicz et al 2013; Zappes et al 2017). These comprised 191 sequences from southern elephant seals and 10 sequences from Weddell seals ( Leptonychotes weddellii ),which we included as an outgroup because they belong to the same subfamily of Phocidae (Slade et al 1994).…”

“…The genetic structure of the breeding colonies of SES have been investigated previously (Hoelzel et al 1993; Slade et al 1998; Fabiani 2002; Chauke 2008; Bogdanowicz et al 2013). However, there remains a gap in our knowledge regarding the natal origins of seals at moulting sites such as Davis Base, where seals potentially from multiple breeding sites aggregate (Bester 1988).…”

Onset and duration of gray seal (Halichoerus grypus) molt in the Wadden Sea, and the role of environmental conditions

“…Within the molt period, though, there is considerable individual variability in timing. In part, this is related to age, sex and internal/ endocrine processes (Bogdanowicz et al 2013). The annual molt occurs sequentially through age-sex classes: first juveniles molt, then adult females, and finally adult males (Boulva and McLaren 1979, Thompson and Rothery 1987, Daniel et al 2003, Cronin et al 2014.…”