Population structure and phylogeography of the Gentoo Penguin (Pygoscelis papua) across the Scotia Arc

Abstract

Climate change, fisheries' pressure on penguin prey, and direct human disturbance of wildlife have all been implicated in causing large shifts in the abundance and distribution of penguins in the Southern Ocean. Without mark‐recapture studies, understanding how colonies form and, by extension, how ranges shift is challenging. Genetic studies, particularly focused on newly established colonies, provide a snapshot of colonization and can reveal the extent to which shifts in abundance and occupancy result from changes in demographic rates (e.g., reproduction and survival) or migration among suitable patches of habitat. Here, we describe the population structure of a colonial seabird breeding across a large latitudinal range in the Southern Ocean. Using multilocus microsatellite genotype data from 510 Gentoo penguin (Pygoscelis papua) individuals from 14 colonies along the Scotia Arc and Antarctic Peninsula, together with mitochondrial DNA data, we find strong genetic differentiation between colonies north and south of the Polar Front, that coincides geographically with the taxonomic boundary separating the subspecies P. p. papua and P. p. ellsworthii. Using a discrete Bayesian phylogeographic approach, we show that southern Gentoos expanded from a possible glacial refuge in the center of their current range, colonizing regions to the north and south through rare, long‐distance dispersal. Our findings show that this dispersal is important for new colony foundation and range expansion in a seabird species that ordinarily exhibits high levels of natal philopatry, though persistent oceanographic features serve as barriers to movement.

Comparative population genomics reveals key barriers to dispersal in Southern Ocean penguins

“…The currently recognized taxonomy of gentoo penguins is for two subspecies, the northern ( Pygoscelis papua papua ) distributed north of 60°S, and the southern ( Pygoscelis papua ellsworthii ) distributed on the Antarctic Peninsula and maritime Antarctic islands south of 60°S (Clements et al., ; Forster, ; Murphy, ). Our data support the existing classification of a northern gentoo subspecies; however, contrary to current taxonomic limits (Clements et al., ), we found that South Georgian gentoos are more closely related to the southern subspecies than the northern, a conclusion that is supported by previous studies of morphology (de Dinechin et al., ), mitochondrial DNA (Clucas et al., ) and microsatellites (Levy et al., ). We recommend formal taxonomic revision of the boundary between northern and southern gentoo penguins to reflect this.…”

“…0.60 Ma (Supporting information Table ). It should be noted that our estimates of divergence time differ markedly from those based on mitochondrial data (Clucas et al., ; Levy et al., ), most likely because mitochondrial data alone were unable to resolve the topology completely, resulting in more recent coalescent events. The same pattern of relatedness was evident from our DAPC and PCA analyses (Figure e, Supporting information S5e).…”

Variation in the ecstatic display call of the Gentoo Penguin (Pygoscelis papua) across regional geographic scales

“…The present study is the most comprehensive analysis of geographic variation in Gentoo Penguin ecstatic calls to date and provides a finer geographic scale at which to examine vocal differentiation. Genetic data from de Dinechin et al (2012) and Levy et al (2016) show the Falkland Islands populations as divergent clades from the Antarctic Peninsula, South Georgia, and the South Orkney Islands. The polar front provides a strong ecological barrier that is likely to maintain this separation and may have led to drift of ecstatic display calls over a long period of geographic isolation.…”

“…In the Atlantic region of their range, the polar front creates a strong ecological boundary between populations in Argentina and the Falkland Islands and those in South Georgia, the South Sandwich Islands, the South Orkney Islands, and the Antarctic Peninsula (Figure 1). This geographic and ecological isolation, combined with high mate and colony fidelity (Lynch 2013), results in strong population genetic structure between regions (Levy et al 2016). There are currently 2 described subspecies, originally based heavily on morphology (Stonehouse 1970) and now confirmed with genetics (de Dinechin et al 2012, Levy et al 2016.…”

“…This geographic and ecological isolation, combined with high mate and colony fidelity (Lynch 2013), results in strong population genetic structure between regions (Levy et al 2016). There are currently 2 described subspecies, originally based heavily on morphology (Stonehouse 1970) and now confirmed with genetics (de Dinechin et al 2012, Levy et al 2016. Pygoscelis papua papua lives above the polar front in the Falkland Islands, and P. p. ellsworthii on the Antarctic Peninsula and subAntarctic islands below the polar front (Levy et al 2016 (2012) proposed a third subspecies for the sub-Antarctic islands above the polar front in the Indian and Pacific oceans.…”