PARENT SESSION
Oral Session #69: Conservation: Biodiversity assessment and reserve design.
Presiding: T. Norton
Wednesday, August 7. 1:00 PM to 4:45 PM. Grand Ballroom Central, Radisson.
Countryside biogeography of tropical herbaceous plants .
Mayfield, Margaret*,1, Daily, Gretchen1, Ehrlich, Paul1, 1 Stanford University, Stanford, CA
ABSTRACT- Increasing amounts of information indicate that a substantial proportion of forest-affiliated animals occur commonly outside extensive tropical forest, in agricultural landscapes. Little is known about the persistence of forest plants in these heterogeneous, countryside habitats. Herbaceous plants directly contribute to native biodiversity and are crucial to the permeability and quality of countryside habitats for native animal life. We surveyed herbaceous plant diversity in 8 common countryside habitat types in southern Costa Rica: pasture, near and far from extensive forest, hedgerows near and far from forest, stream edges within and far from forest, and tree-fall gaps within and at the edge of forest. 850 species from 80 angiosperm families were found in our study. Forest sites had significantly higher species richness and significantly lower average species abundance than pasture or hedgerow sites. Preliminary results indicate that up to 80 % of the plant families and 60 % of species in this study are found in both forest and pasture habitats. The majority of these cosmopolitan species occur in forest tree-fall gaps, pasture-stream edges and near forest edges. Patterns are very taxon-specific, with the Asteraceae and Melastomataceae representing the most cosmopolitan families. Only about 15 % of families are restricted to forested sites. These results are promising for conservation prospects, but should be interpreted with caution. Ongoing intensification of land use threatens to diminish the conservation value of human dominated tropical countryside.
KEY WORDS: Biodiversity, Countryside biogeography, Costa Rica