High mitochondrial and nuclear genetic diversity in one of the world’s most endangered seabirds, the Chatham Island Taiko (Pterodroma magentae)

Abstract

Interpreting the levels of genetic diversity in organisms with diverse life and population histories can be difficult. The processes and mechanisms regulating this diversity are complex and still poorly understood. However, endangered species typically have low genetic variation as a consequence of the effects of genetic drift in small populations. In this study we examine genetic variation in the critically endangered Chatham Island Taiko (Tchaik, Pterodroma magentae), one of the world’s rarest seabirds. The Taiko has a very small population size of between 120 and 150 individuals, including just 8–15 breeding pairs. We report surprisingly high mitochondrial and nuclear genetic diversity in this critically endangered long-lived species. We hypothesise that the present Taiko population has retained a significant proportion of its past genetic diversity. However, it is also possible that undiscovered birds are breeding in unknown areas, which could increase the population size estimate. Importantly, from a conservation perspective, we show that the high level of variation is unlikely to be maintained in the future since chicks currently being born have only a limited number of the mitochondrial DNA haplotypes found in adults. Reduced genetic variation will mean that our ability to infer past events and the population history of Taiko using genetics could soon be lost and the power to determine, for example, parentage and other close order relationships will be diminished. Therefore, the maintenance of genetic diversity in future generations is an important consideration for conservation management of the Taiko.