PARENT SESSION
Oral Session #101: Plant-Animal Interactions.
Presiding: S. Faeth
Friday, August 9. 9:00 AM to 12:00 PM. Coconino Meeting Room, TCC.
Elephant ranging and tree distribution in a Congo Forest.
Walsh, Peter*,1,2, Blake, Stephen2,3, 1 Dept. of Ecology & Evolutionary Biology, Princeton, NJ2 Africa Program, New York, NY3 Edinburgh University, Edinburgh, Scotland
ABSTRACT- How will the rapid decline of large vertebrates affect the dynamics of tropical forests? We used transect samples distributed over a large spatial scale to examine how seed dispersal mode, particularly dispersal by elephants, influenced the spatial distribution and phenology of trees. Within species tree aggregation decreased in the following order: gravity dispersed, wind dispersed, species dispersed by animals other than elephants, trees dispersed by elephants and other animals, trees dispersed only by elephants. For elephant dispersed species, the degree of within species aggregation was negatively correlated with an index of elephant preference. The rate at which similarity in species composition decayed in space followed the same order as within species aggregation: similarity decayed most slowly for obligate elephant species. Finally, autocorrelation in fruiting phenology decayed more slowly in space for elephant dispersed species than for species dispersed by other animals. These results suggest that disperser body size, through its effect on ranging scale, has a profound effect on competition between animal and abiotically dispersed trees. Local extinction of large vertebrates will probably lead to a catastrophic reduction of species in the now rich, animal dispersed guild. Unfortunately, the impact on tree diversity may not become apparent until long after large vertebrates are extirpated. Small reserves may be of little utility in protecting African tree species diversity in the long term.
KEY WORDS: forest elephant, reserve design, tree diversity, spatial autocorrelation