Lack of genetic differentiation among subpopulations of the black-footed albatross on the Bonin Islands

The endangered black-footed albatross Phoebastria nigripes exhibits strong nest fidelity and natal philopatry. These biological features can strongly affect population dynamics and population genetic structure. Therefore, for its long-term conservation, it is important to estimate genetic diversity and population genetic structure. We performed genetic analyses, using 11 polymorphic microsatellite markers of 77 black-footed albatrosses from six breeding colonies on the Bonin Islands, an important breeding area in the western North Pacific. In the population-based analysis, AMOVA results showed that almost all genetic variations existed among individuals in each subpopulation. Most F-ST and R-ST values among the subpopulations were 0.000 and the migration rates were 3.0-5.3%. In the individual-based analysis, the results of structure analysis suggested that all the individuals were clustered into the same genetic group. In the principal coordinates analysis based on kinship among individuals, most of the individuals were distributed as a single group. Although albatross species are strongly philopatric, the present results indicate a lack of population genetic differentiation among six subpopulations and the presence of sufficient gene flow to maintain the genetic homogeneity. In the principal coordinates analysis, a few individuals were genetically different from most of the other individuals, indicating a probability of immigration. The black-footed albatrosses on the Bonin Islands are in a good condition to maintain genetic diversity and can be treated as a single genetic management unit.