Spatial genetic architecture of the critically-endangered Maui Parrotbill (Pseudonestor xanthophrys): management considerations for reintroduction strategies

Conservation translocations are an important tool to circumvent extinctions on oceanic islands. A thorough understanding of all components of a species’ biology, including genetic diversity and structure, can maximize their likelihood of success. The Maui Parrotbill (Pseudonestor xanthophrys) is an endangered Hawaiian honeycreeper endemic to the island of Maui. With a population of approximately 500 individuals restricted to 50 km2 of habitat, this species is at high risk of extinction. Using nuclear and mitochondrial DNA, this study quantified the levels of genetic diversity and structure in wild and captive parrotbill populations, and compared these genetic patterns to those observed within levels of contemporary and historical nuclear diversity derived from 100-year old museum samples. Substantial differences in the effective population sizes estimated between contemporary and historical parrotbill populations highlight the impact that introduced disease had on this species just before the turn of the century. Contemporary parrotbill diversity was low (global F st = 0.056), and there has been a 96 % reduction in genetic effective population size between contemporary and historical samples. This should not eliminate a conservation translocation (or reintroduction) as a viable recovery option. Measures of population differentiation (pairwise F st and R st ) between different sections of the current population on either side of the Koolau Gap suggest that current genetic structure may be the result of this topographic barrier to gene flow. These data can enable the design of a conservation translocation strategy that is tailored to the patterns of genetic structure across the species’ range.