, Volume 147, Issue 2, pp 238-252
Date: 03 Dec 2005

Enhanced seed dispersal of Prunus africana in fragmented and disturbed forests?

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Abstract

Forest destruction and disturbance can have long-term consequences for species diversity and ecosystem processes such as seed dispersal. Understanding these consequences is a crucial component of conserving vulnerable ecosystems. In the heavily fragmented and disturbed Kakamega Forest, western Kenya, we studied seed dispersal of Prunus africana (Rosaceae). In the main forest, five forest fragments, and differently disturbed sites, we quantified the overall frugivore community as an indicator for species diversity. Furthermore, we determined the frugivores on 28 fruiting P. africana trees, estimated seed dispersal, crop size and the general fruit availability of surrounding trees. During the overall frugivore census we recorded 49 frugivorous species; 36 of them were observed visiting P. africana trees and feeding on their fruits. Although overall frugivore species richness was 1.1 times lower in fragments than in main forest sites and 1.02 times higher in highly disturbed than in less disturbed sites, P. africana experienced 1.1 times higher numbers of frugivores in fragments than in main forest sites and 1.5 times higher numbers of frugivores in highly disturbed than in less disturbed sites. Correspondingly, seed dispersal was 1.5 times higher in fragments than in main forest sites and 1.5 times higher in more disturbed than less disturbed sites. Fruit availability of surrounding trees and crop size influenced the number of visitors to some degree. Thus, the number of dispersed seeds seemed to be slightly higher in fragmented and highly disturbed sites. This indicates that loss of single species does not necessarily lead to a decrease of ecosystem services. However, loss of diversity could be a problem in the long term, as a multitude of species might act as buffer against future environmental change.

Communicated by Ingolf Steffan-Dewenter