Population-Genetic Structure of a Philopatric, Colonially Nesting Seabird, the Short-Tailed Shearwater (Puffinus tenuirostris)

Short-tailed Shearwaters (Puffinus tenuirostris) are a numerous, colonially nesting seabird that is strongly philopatric. We applied restriction-enzyme analysis of mitochondrial DNA (mtDNA) to 335 individuals from 11 colonies across southeastern Australia to assess population-genetic structure and the amount of genetic variability in this species. Eleven 6/5.33-base and four 4-base restriction enzymes revealed 25 and 48 mtDNA haplotypes in two overlapping surveys of 215 individuals from seven colonies and 231 individuals from eight colonies, respectively. A low mean sequence diversity among individuals (0.247%) and lack of spatial structuring of mtDNA haplotypes suggest a lack of population-genetic structure and a reduced ancestral population size during glaciation, followed by a population and range expansion. Intracolony mtDNA diversities in three recently established colonies and in one colony that has experienced a recent bottleneck were comparable to mtDNA diversities within larger and older colonies. This suggests that, despite strict philopatry in those colonies, colony founding and recovery from population reduction occurs via immigration of a large number of individuals.