Evidence for a single panmictic and genetically diverse population of the coconut crab Birgus latro (Decapoda: Anomura: Coenobitidae) on Christmas Island in the Indian Ocean

Abstract

For the coconut crab Birgus latro, Christmas Island in the Indian Ocean may be one of the last retreats where populations of this declining species are not threatened by overharvesting, as on many other mostly tropical Indo-Pacific islands within the species’ wide range. Nevertheless, the population on Christmas Island has experienced severe losses during the past decade owing to habitat destruction and road mortality. To assess the population’s evolutionary potential and identify the number of conservation units, we conducted a combined morphometric and population genetic analysis using microsatellite markers. The findings suggest that the population is genetically diverse and panmictic. Neither genetic nor morphometric analyses revealed any population substructuring. There was no genetic evidence for sex-biased dispersal. Single-sample estimators for the effective population size (Ne) ranged from 492 to infinity, with very wide confidence intervals; they should therefore be viewed with caution. It would be advisable to reanalyse Ne, preferably by temporal methods. Despite mixed results, there is stronger evidence against rather than for the occurrence of a recent genetic bottleneck. So far, the population of B. latro on Christmas Island may be considered as a single conservation management unit, this way simplifying future conservation efforts taken for this magnificent species.