Genetic distinctiveness of Masked Booby (Sula dactylatra) on Bedout Island, Western Australia

The Masked Booby is a highly vagile, pantropical seabird of which up to six subspecies have been recognised: S. d. dactylatra, S. d. californica, S. d. personata, S. d. melanops, S. d. bedouti and S. d. tasmani. The genetic distinction of several S. dactylatra colonies has been previously investigated, but this has not yet been conducted for the Bedout Island population in Western Australia, which has been considered by some to be part of a distinct subspecies.

Suspected population decline on Bedout Island has renewed interest in determining the extent to which genetic novelty might be threatened. To answer this question, morphological and mitochondrial control region sequence variation were used to determine the distinction of the Bedout Island population. Whereas the morphological measures were equivocal, six haplotypes were identified from 31 individuals, none of which were shared by individuals previously sampled from the Indo-Pacific.

The Bedout Island haplotypes were most closely related to other haplotypes found in a distinct Indian Ocean haplogroup, but haplotype frequencies at Bedout Island differed significantly from all other. This indicates that the Bedout Island population rarely exchanges mitochondrial genes with any of the other Masked Booby colonies presently studied, which may reflect dependence on local recruitment for its persistence.