| Forest fragmentation is one of the most serious global environmental problems. Worldwide, large continuous tracts of forest are increasingly being reduced to small forest fragments within diverse matrices of human-dominated land uses. It is important to understand what impacts these anthropogenic landscape changes are having on natural communities. To investigate the effects of forest fragmentation, I used a variety of methods including surveys of tropical bat communities in regions with varying degrees of forest clearing, radio telemetry studies to locate bat roosts in fragmented tropical and temperate landscapes, surveys of local habitat use and seed dispersal by birds and bats in mature tropical forest and adjacent human-disturbed vegetation, and guild and ecomorphological analyses. My results provide insight into (i) the effects of forest fragmentation on bat community structure and composition, (ii) the relative vulnerability of different groups of species in fragmented forests, and (iii) patterns of seed dispersal within fragmented tropical landscapes. With respect to bat community structure, I found that, at a regional level, overall bat species richness increased with increasing fragmentation due to the addition of disturbance-associated species without concurrent loss of forest species. More locally, however, both richness and abundance decreased in the most disturbed vegetation classes. Bat species most forest-restricted locally declined in relative abundance with increasing fragmentation. Among insectivorous bat species, relative activity in forest versus disturbed vegetation was strongly correlated with minimum echolocation frequency. With respect to vulnerability, I found that, while birds and bats within the same foraging guild showed similar vulnerability, many vulnerable guilds contained only birds. Consequently, bats were less liable to extinction in fragmented landscapes than birds. Finally, with respect to seed dispersal, I found that birds and bats dispersed seeds to different locations. Bird dispersal dominated in treefall gaps and at forest edges, while bat dispersal dominated in closed canopy forest and in manmade clearings. Although fruit-eating bats foraged in disturbed vegetation, they roosted in large trees in mature forest patches. The loss of remnant forest patches could cause declines in populations of seed-dispersing bats, threatening natural restoration of fragmented tropical forests. |
