Mechanisms of population differentiation in seabirds

Abstract

Despite recent advances in population genetic theory and empirical research, the extent of genetic differentiation among natural populations of animals remains difficult to predict. We reviewed studies of geographic variation in mitochondrial DNA in seabirds to test the importance of various factors in generating population genetic and phylogeographic structure. The extent of population genetic and phylogeographic structure varies extensively among species. Species fragmented by land or ice invariably exhibit population genetic structure and most also have phylogeographic structure. However, many populations (26 of 37) display genetic structure in the absence of land, suggesting that other barriers to gene flow exist. In these populations, the extent of genetic structure is best explained by nonbreeding distribution: almost all species with two or more population-specific nonbreeding areas (or seasons) have phylogeographic structure, and all species that are resident at or near breeding colonies year-round have population genetic structure. Geographic distance between colonies and foraging range appeared to have a weak influence on the extent of population genetic structure, but little evidence was found for an effect of colony dispersion or population bottlenecks. In two species (Galapagos petrel, Pterodroma phaeopygia , and Xantus's murrelet, Synthliboramphus hypoleucus ), population genetic structure, and even phylogeographic structure, exist in the absence of any recognizable physical or nonphysical barrier, suggesting that other selective or behavioural processes such as philopatry may limit gene flow. Retained ancestral variation may be masking barriers to dispersal in some species, especially at high latitudes. Allopatric speciation undoubtedly occurs in this group, but reproductive isolation also appears to have evolved through founder-induced speciation, and there is strong evidence that parapatric and sympatric speciation occur. While many questions remain unanswered, results of the present review should aid conservation efforts by enabling managers to predict the extent of population differentiation in species that have not yet been studied using molecular markers, and, thus, enable the identification of management units and evolutionary significant units for conservation.

On the origin of Halipeurus heraldicus on Round Island petrels: Cophylogenetic relationships between petrels and their chewing lice

“…arminjoniana on Trindade and Round island shows significant population structure between them, in the form of a significant F ST value (Brown et al, submitted-b). However, this structure is weak when compared with other Procellariiform species which have populations in different ocean basins (Friesen et al, 2007), supporting the theory that the two populations of Pt. arminjoniana have recently split from one another (Brown et al, submitted-b).…”

Long-term isolation of a highly mobile seabird on the Galapagos

“…Seabirds from the South American mainland, however, tend to forage in the nearby and highly productive upwelling zone along the continental shelf [41], so many of them may not venture out far from the coast. A recent review of seabird population structuring [42] found that most populations occupying separate ranges during the non-breeding season also display population genetic structure. Our results regarding the Galapagos population could thus be explained by geographical/ foraging range isolation.…”

Breeding site fidelity and winter admixture in a long-distance migrant, the tufted duck (Aythya fuligula)

“…In most cases, these flyways have been delimited based on mark-recapture data but, in many species, they are also supported by the molecular data (mostly mtDNA), that is, in passerines (Ruegg and Smith, 2002;Clegg et al, 2003;Pérez-Tris et al, 2004), waders (Wennerberg, 2001) and several species of waterfowl (Scribner et al, 2001;Gay et al, 2004). Similarly, Friesen et al, (2007) found that a majority of seabirds with discontinuous distributions on the breeding or wintering grounds showed some genetic substructure. Sometimes, genetic divergence across migratory divides is only observed for one marker type, typically mtDNA in species with male-biased dispersal (Scribner et al, 2001;Gay et al, 2004), but we are aware of only two other studies where it was absent altogether (Pearce et al, 2004;Liu et al 2011).…”