Lee-Sim Lim

Past climate change and recent human activity have had major impacts on the
distribution of habitats as well as the community and population genetic structure of the
species occupying these habitats. In temperate zones, glaciation forced many taxa into
southern refugia. In contrast, little is understood about the extent to which tropical taxa
and habitats were affected by colder periods. In Southeast Asia, some argue that the
tropical forest was replaced by savannah at the Last Glacial Maximum (LGM), whereas
others suggest that the forest persisted. Studying population genetic and community
structure of forest-dependent species in this region may shed light on which of these
scenarios is most likely, as well as provide crucial information on the effects of recent
habitat loss. To address these issues, I studied the genetic and community structure of
forest-dependent insectivorous bat species in Peninsular Malaysia. Data collected at 22
sites indicated that species richness declined with latitude, consistent with post-glacial
expansion of forest. To test this further, I undertook mitochondrial DNA sequencing of
a widespread species, Rhinolophus affinis, and found high haplotype diversity, little
phylogeographic structure and no demographic growth. These all suggest a long
population history in the region with no post-LGM range expansion. Subsequent
microsatellite analyses of R. affinis and the congeneric R. lepidus showed that genetic
distance followed an isolation-by-distance model, and that allelic diversity was
unexpectedly higher in the northern populations. Taken together, my results from the
community and genetic analyses disagree with each other. These conflicts are perhaps
best explained if observed clines in species richness pre-date the LGM. I conclude that
there is little evidence of forest contraction in the LGM. The fact that the highest species
diversity was detected in the south, which is experiencing the most forest loss due to
human activity, has important conservation consequences.