Genetic variation in the kakerori (Pomarea dimidiata), an endangered endemic bird successfully recovering in the Cook Islands

Abstract

The Cook Islands endemic kakerori (Pomarea dimidiata) underwent a severe population decline following the introduction of ship rats (Rattus rattus) in the late 1800s. By 1989, the sole population on Rarotonga consisted of 29 known birds. Subsequent intensive management efforts enabled this population to recover to around 250–300 birds in recent years. This study, using microsatellite and mitochondrial DNA markers, assesses the level of genetic diversity and the genetic structure of the contemporary kakerori population on Rarotonga. No mitochondrial control region and cytochrome b haplotype diversity was found in the 11 samples examined at each locus. In 81 samples genotyped at 7 polymorphic microsatellite loci, an average of 4 alleles per locus were found, with an average observed heterozygosity of 0.65. No subpopulation division was found in this population. There was no evidence of inbreeding, but genetic bottleneck tests showed that the population had indeed experienced a significant genetic bottleneck. Recovery of the kakerori was successful in the past two decades despite low genetic diversity in terms of allelic diversity. Our data suggested that low allelic diversity did not hamper population expansion and the continued survival of this species, however, longer-term effects are still possible.