Abstract
BackgroundIn seabirds, the extent of population genetic and phylogeographic structure varies extensively among species. Genetic structure is lacking in some species, but present in others despite the absence of obvious physical barriers (landmarks), suggesting that other mechanisms restrict gene flow. It has been proposed that the extent of genetic structure in seabirds is best explained by relative overlap in non-breeding distributions of birds from different populations. We used results from the analysis of microsatellite DNA variation and geolocation (tracking) data to test this hypothesis. We studied three small (130–200 g), very abundant, zooplanktivorous petrels (Procellariiformes, Aves), each sampled at two breeding populations that were widely separated (Atlantic and Indian Ocean sectors of the Southern Ocean) but differed in the degree of overlap in non-breeding distributions; the wintering areas of the two Antarctic prion (Pachyptila desolata) populations are separated by over 5000 km, whereas those of the blue petrels (Halobaena caerulea) and thin-billed prions (P. belcheri) show considerable overlap. Therefore, we expected the breeding populations of blue petrels and thin-billed prions to show high connectivity despite their geographical distance, and those of Antarctic prions to be genetically differentiated.ResultsMicrosatellite (at 18 loci) and cytochrome b sequence data suggested a lack of genetic structure in all three species. We thus found no relationship between genetic and spatial structure (relative overlap in non-breeding distributions) in these pelagic seabirds.ConclusionsIn line with other Southern Ocean taxa, geographic distance did not lead to genetic differences between widely spaced populations of Southern Ocean petrel species.
Highlights
In seabirds, the extent of population genetic and phylogeographic structure varies extensively among species
Friesen et al [4] suggested that the extent of genetic structure in seabirds could be explained by the overlap of non-breeding areas, as most species with two or more population-specific non-breeding areas showed phylogeographic structure
During 2010–2012, blood samples were obtained from adult birds breeding in colonies of thin-billed prions located at Île Mayès, Kerguelen (49°28′S, 69°57′E; N = 34) and New Island, Falkland/Malvinas Islands (51°43′S, 61° 18′W; N = 42); Antarctic prions at Île Verte, Kerguelen (49°30′S, 70°02′E; N = 38) and Bird Island, South Georgia (54°00′S, 38°02′W; N = 35); and blue petrels at Île Mayès (N = 30) and Bird Island (N = 19)
Summary
The extent of population genetic and phylogeographic structure varies extensively among species. Genetic structure is lacking in some species, but present in others despite the absence of obvious physical barriers (landmarks), suggesting that other mechanisms restrict gene flow. It has been proposed that the extent of genetic structure in seabirds is best explained by relative overlap in non-breeding distributions of birds from different populations. We expected the breeding populations of blue petrels and thin-billed prions to show high connectivity despite their geographical distance, and those of Antarctic prions to be genetically differentiated. Seabirds in the Southern Ocean are faced with a limited availability of habitable islands, resulting in disjunctive breeding distributions, with populations often located at island groups that are several thousand kilometres apart [3]. Because geographical barriers are absent across the Southern Ocean, physical isolation by geographic landmarks may not restrict gene flow. Integrative studies of both population genetic structure and at-sea distributions are required to understand evolutionary processes in these taxa
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