Inferring colonization history and dispersal patterns of a long‐lived seabird by combining genetic and empirical data

Abstract

Identifying biological trends and threats to organisms that make long distance migrations are often the limiting factors in their conservation. Indeed, Laysan albatross Phoebastria immutabilis are highly vagile seabirds, foraging throughout the North Pacific Ocean. Despite mark-recapture data indicating natal philopatry, Laysan albatross recently re-colonized several anthropogenically extirpated breeding locations. At the same time, a breeding population in the north-western Hawaiian Islands was lost to erosion and it was hypothesized that the colonization events were due to displacement rather than dispersal. Nuclear and mitochondrial markers were used in a range wide survey to test whether natal philopatry corresponded to population structure in Laysan albatross, and to determine whether recent colonization events were a result of displacement from vanishing breeding habitat. Five microsatellite loci found little population structure (F ST = 0.01, P= 0.001), and sequences from the mitochondrial control region revealed low population structure (p ST = 0.05, Po0.001). The results were consistent with male-mediated dispersal and strong, but not absolute, philopatry by females. Mixed stock analyses and banding records from the newly colonized sites indicated contributions from multiple source populations, which contradicted the displacement hypothesis of a single source population and instead supported species-wide dispersal from all source colonies. High genetic diversity (p= 0.045, h = 0.989), rapid colonization, and great dispersal potential bode well for the conservation of Laysan albatross. However, it may be necessary to protect highisland nesting sites, preserve genetic diversity and maintain breeding populations in the face of projected sea level rises and persistent bycatch.

Population divergence and gene flow in an endangered and highly mobile seabird

“…A total of 322 Hawaiian petrel samples were obtained from across the current and historical breeding range of this species (Table 1, Figure 1). Modern samples (N¼294) consisting of blood, muscle or other tissue, bone and feather were salvaged from carcasses of birds depredated in breeding colonies on Hawaii, Maui, Lanai andKauai, between 1990 and2010, or collected from birds that were handled during conservation management procedures, such as rehabilitation following power-line strikes or crashes due to disorientation caused by artificial light sources (Podolsky et al, 1998). Crashed birds and carcasses were assumed to be breeders (or the offspring of breeders) on the island where they were discovered, as nonbreeders depart during the first half of chick-rearing (Simons, 1985;Simons and Hodges, 1998).…”

“…If petrels are able to overcome isolating mechanisms and disperse prior to complete extirpation then this could explain why some species do not seem to exhibit population genetic differentiation, despite evidence of strong philopatry from mark-recapture studies. For example, the Laysan albatross is known to exhibit strong natal philopatry (Fisher, 1976), but very weak population structure was found in this species (Young, 2010). While density-dependent dispersal was suggested as one potential cause, displacement from several extirpated colonies could also lead to weak population structure.…”

Identifying mechanisms of genetic differentiation among populations in vagile species: historical factors dominate genetic differentiation in seabirds

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Genetic panmixia in New Zealand's Grey-faced Petrel: implications for conservation and restoration

“…For example, Morris-Pocock et al (2008) found genetic structure in Atlantic Common Murres (Uria aalge) owing to historical fragmentation even with high contemporary gene flow. The limited population structure observed among Laysan Albatrosses (Phoebastria immutabilis) is likely a result of both historical and current gene flow, because the birds started recolonising many anthropogenically extirpated breeding sites in the 1970s (Young 2010).…”