Population genetic structure of the insular Ryukyu flying fox Pteropus dasymallus

Small isolated populations are vulnerable to both stochastic events and
the negative consequences of genetic drift. For threatened species, the
genetic management of such populations has therefore become a crucial
aspect of conservation. Flying foxes (Pteropus spp, Chiroptera)
are keystone species with essential roles in pollination and seed
dispersal in tropical and subtropical
ecosystems. However, many flying fox species are also
threatened, having experienced dramatic population declines driven by
habitat loss and hunting. The insular Ryukyu flying fox (Pteropus
dasymallus) ranges from the Ryukyu Archipelago of Japan through Taiwan to
the northern Philippines and has undergone precipitous population crashes
on several islands in recent decades. To
assess the population genetic structure and diversity
in P. dasymallus, and its likely causes, we analyzed
mitochondrial and microsatellite DNA. Both markers showed significant
genetic differentiation among most island populations, with mitochondrial
haplotypes showing some mixing across the region, likely reflecting
historical colonization and/or dispersal events. In contrast,
microsatellite markers showed an overall pattern of isolation by
distance; however, this pattern appeared to be
driven by the presence of deep ocean trenches between geographically
distant populations. Thus the current distribution of P.
dasymallus and its subspecific diversity appears to have arisen
through vicariance coupled with a long history of restricted gene flow
across oceanic barriers. We conclude that isolated island subgroups should
be managed separately, with efforts directed at reducing further declines
in genetic diversity.