PARENT SESSION
Oral Session #24: Conservation and Biodiversity: Birds and arthropods.
Presiding: C. Bock
Monday, August 5. 1:00 PM to 3:45 PM. Mesquite Room, Radisson.
Spatial organization of diversity in tropical montane forest avifaunas: implications for persistence of endemic species.
Rabenold, Kerry*,1, Jankowski, Jill1, 1 Department of Biological Sciences, West Lafayette, IN
ABSTRACT- We investigate the rate of change in species composition of bird communities across a variety of scales in the mountain forests of Costa Rica. Understanding how high regional biodiversity of areas like Central America is partitioned between local (alpha) diversity of small areas (10-100ha) within particular habitat types, and landscape (beta) diversity over larger areas encompassing multiple habitats, is a longstanding conceptual goal in ecology and an important guide for conservation planning. If species are sufficiently specialized for particular forest types along an altitudinal gradient, beta diversity will be high and regionally endemic species may be further limited spatially on a local scale. We ask whether habitat specialization is associated with rarity within habitat types, resulting in a syndrome of vulnerability for regional endemics that are rare at all scales. We find strong similarity of species composition at a particular altitude (lower montane rainforest), both within the Monteverde Cloudforest Reserve, and between neighboring reserves in the Tilaran range. Using comparisons with other studies, we find differences increasing with distance among mountain ranges. Species composition changes rapidly with altitude on tropical mountains, especially on the Pacific slope of Costa Rica, and our data show surprisingly rapid change even within recognized life zones. At the highest elevations, where the impact of climate change is greatest, species with geographically limited ranges tend to also have narrow ecological tolerances and to be rare within their habitats. This accumulation of risk factors makes these endemics particularly vulnerable to extinction.
KEY WORDS: tropical forest, species diversity, endemic species, bird community