Population genetic structure in 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. Yet many flying fox species are also of conservation concern, having experienced dramatic population declines driven by habitat loss and hunting. The Ryukyu flying fox (Pteropus dasymallus) ranges from Japan and Taiwan to the northern Philippines, and has undergone precipitous population crashes on several islands in recent decades. To assess 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 patterns of isolation-by-distance. However, while mitochondrial haplotypes showed some mixing across the region, likely reflecting historical colonization and/or dispersal events, microsatellites markers showed clear subdivisions corresponding to the position of deep ocean trenches. The current distribution of P. dasymallus and its subspecific diversity therefore 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.

Siebold and Temminck on the distribution of Pteropus dasymallus, the Ryukyu Flying Fox

Philipp Franz von Siebold (1796–1866) was one of the earliest European naturalists to live in Japan. Through most of the nineteenth century, however, until the 1860s, movement of foreigners within Japan was severely restricted, impairing Siebold's ability to observe wildlife in the countryside or collect zoological specimens. Among the Japanese mammals that Siebold was able to see, if not necessarily in the wild, and acquire examples of, was Pteropus dasymallus, the Ryukyu Flying Fox. On the basis of Siebold's early work, Coenraad Jacob Temminck (1778–1858), in 1825, first described the species scientifically. Siebold's initial observations on the fruit bat's range, however, proved to be incorrect. His notes on the species' distribution in and around Nagasaki in southern Kyushu and Tokyo in central Honshu were particularly contradictory, apparently based, at least in part, upon an initial confusion with either Pteromys petaurista (Japanese Giant Flying Squirrel) or Pteromys momonga (Japanese Dwarf Flying Squirrel).

Variation in the nocturnal foraging distribution of and resource use by endangered Ryukyu flying foxes (Pteropus dasymallus) on Iriomotejima Island, Japan

The nocturnal distribution and resource use by Ryukyu flying foxes was studied along 28 transects, covering five types of habitats, on Iriomote Island, Japan, from early June to late September, 2005. Bats were mostly encountered solitarily (66.8%) or in pairs (16.8%), with a mean linear density of 2.5 ± 0.6 bats/km of transect/night. Across the island, however, bat densities were distributed non-randomly among transect-nights, not correlated with transect length, and showed a slightly clumped distribution (variance/mean = 3.3). Outskirt trails contributed higher values to the relative importance of bat abundance, but the highest mean abundances occurred mostly at village sites on the west coast, which on average devoted only a quarter of their land area to agriculture/husbandry compared to those on the east coast. This supports our prediction that higher bat abundances are found in areas with less anthropogenic interference and more forest. Among habitats, the mean total abundance and density were lower in cultivated areas than in villages and inland forests. Bat perches in cultivated areas were also lower, and were in correspondence with lower shrub and canopy heights, and less canopy coverage. Flying fox abundance was correlated moderately with the heterogeneity of the tree composition, and strongly with the density of major fruiting trees. Thirty-nine species of plants and some animal items were used by Ryukyu flying foxes, including at least 31 species of fruits, 13 species of flowers, and leaves of seven species, with 14 species new to the record. Ficus septica and F. variegata were the most frequently encountered and dominant items in both fecal and rejecta/dropped samples, followed mostly by other figs and mulberries in the former, but by larger-seed non- Moraceae plants in dropped samples. Our results suggest that for conservation of flying foxes undisturbed forests providing an adequate resource basis are of major importance.