Inter‐island movements and population differentiation in a pelagic seabird

Abstract

We used mark-resight data and amplified fragment length polymorphism (AFLP) markers to assess movements and gene flow between Central Pacific breeding colonies of the great frigatebird, Fregata minor. Of 715 adult frigatebirds marked on Tern Island and Johnston Atoll, 21.3% were resighted at other frigatebird colonies at least 582 km away. Mark-resight data indicated regular movement of males and females between Tern Island and Johnston Atoll (873 km apart), and less frequent movements to other islands; no birds marked on Tern or Johnston were seen on Christmas Island, but one was seen in the Philippines, 7627 km from where it was marked. Despite the regular occurrence of interisland movements, Bayesian analyses of AFLP data showed significant genetic differentiation between Tern Island and Johnston Atoll, and more pronounced differentiation between these two islands and the more distant Christmas Island. The AFLP profiles of three birds breeding on Tern Island fell within the profile-cluster typical for Christmas Island birds, both in a nonmetric multidimensional scaling analysis and in a population assignment test, suggesting dispersal events from Christmas Island to Tern Island. Several factors could explain the persistence of genetic structure despite frequent movements between colonies: many movements occurred during the nonbreeding season, many breeding-season movements did not involve mate-acquisition behaviours and individuals that do disperse may be selected against, as suggested by morphometric differences between colonies. The persistence of genetic structure among breeding colonies despite significant interisland movements suggests limits to the effectiveness of migration as a homogenizing force in this broadly distributed, extremely mobile species.

Seasonal shifts in foraging distribution due to individual flexibility in a tropical pelagic forager, the Ascension frigatebird

“…Because there is no nearby land mass, Ascension frigatebirds may not be able to migrate to other roosting areas as has been speculated for frigatebirds in the equally isolated Galapagos archipelago , although the nearest island of Saint Helena is only marginally farther (1250 km) than the maximum distance from the colony recorded in our study. The somewhat limited dispersal outside the breeding season, which does not appear to overlap with the foraging area of any other frigatebird species, may have led to genetic isolation and contributed to the speciation of Ascension frigatebirds (Dearborn et al 2003).…”

Population genetics of the common guillemot, Uria aalge, in the North Atlantic: geographic impact of oil spills

“…However, it is now well known that young auks may settle and start breeding away from their natal colony (e.g. Harris & Wanless 1991, Halley & Harris 1993, Lyngs 1993, Harris et al 1996a, Olsson et al 1999, Harris & Swann 2002 Dearborn et al 2003). Most of these studies have used markers that typically reflect the phylogeographic history of the species rather than provide information on current gene flow (e.g., mitochondrial DNA markers), and a call for the use of more polymorphic markers, such as microsatellites, has been made (Moum & Arnason 2001).…”

Population structure in a highly pelagic seabird, the Cory’s shearwater Calonectris diomedea: an examination of genetics, morphology and ecology

“…Thus, disentangling introgression from immigration requires an assessment of geographic variation in phenotypic and genetic patterns, combined with contemporary records regarding movements. This is particularly important in the case of seabirds because dispersal among breeding localities is common in many species (Goostrey et al 1998, Pons et al 2004), but does not necessarily lead to successful breeding and thus effective gene flow (Dearborn et al 2003). Indeed, most studies are based on a single data source (e.g.…”