Molecular insight on the diversification of Philippine horseshoe bats.

摘要

The more than 7,000 islands of the Philippine archipelago make up one of the planet's most impressive biological hotspots. They are located in the tropics and primarily rose de novo from the ocean floor, creating opportunities for colonizing species that have resulted in high levels of both species richness and endemism. Using knowledge of the geological history of island formation and effects of climatic cycles on island size and isolation as a framework, I tested variation in several species of horseshoe bats (genus Rhinolophus) against the predicted patterns of geographical diversification.I used genetic variation in mitochondrial DNA to reconstruct phylogeographic history of Rhinolophus arcuatus, R. inops and R. virgo. Neither R. arcuatus nor R. inops represent monophyletic units, but rather have been applied as names for groups that are similar in body size. The body size differences between these groups have evolved multiple times and some R. arcuatus are more closely related to R. inops than their supposed conspecifics. Subtle morphological variation in the noseleaf is associated with greater genetic divergence and can be used to identify phylogenetically relevant groups within similar body size classes. Groups within these species differ in their geographical distributions: one may be restricted to Mindanao, whereas the other three groups are known throughout much of the archipelago and show differences in their elevational ranges. I also found genetic subdivision in Rhinolophus virgo that is more consistent with multiple cryptic taxa than a single widespread species. However, there was substantially less sympatry of related lineages than found in the R. arcuatus-inops complex. One lineage was found only on Palawan, another only on Mindanao, a third primarily on Negros and Panay, and the fourth lineage was relatively widespread occurring on many islands in the northern and central areas of the country. Rhinolophus virgo therefore is much more reflective of the low sea level arrangement of islands during the Pleistocene that are responsible for many biogeographic patterns within the archipelago. Finally, I returned to studying the first two nominal species, R. arcuatus and R. inops, by using variation in nuclear microsatellite loci. These data are consistent with cryptic diversity and a relatively labile condition for body size, emphasizing a large role for discordant rates of morphological and molecular evolution.This study shows that biological diversity in the Philippines remains underestimated in both raw numbers and measures of endemism, yet it is at risk of significant loss due to deforestation and other ecological effects of human population size. Understanding the evolutionary history of the second largest segment of the mammalian fauna is an important element to be incorporated in conservation planning and can directly improve assessment and monitoring programs by identifying actual populations, considering multiple possible outcomes from a single geographic setting, and overcoming biases such as that all organisms capable of flight have high dispersal tendencies.