<S1-6> Gene flow through pollination of dipterocarp tree species in a Bornean rainforest

Abstract

We used microsatellite DNA analysis to assess the gene flow through pollination and the fine-scale spatial genetic structure (FSGS) of dipterocarp tree species in a tropical rain forest in Borneo. The results suggest that the intensity of FSGS of dipterocarp populations is dependent on tree density and pollination system. We found notable FSGS in beetle-pollinated tree populations but not in bee-pollinated tree populations. Both high and low density beetle-pollinated species had clear FSGS, in which genotypes of nearby trees were similar but those of distant trees were genetically different from each other. FSGS was especially strong for beetle-pollinated species with low tree density. These results are particularly important because they suggest that the effects of forest fragmentation by logging might be largely dependent on individual tree species. Logging is likely to form fragmented populations consisting of patches of genetically related trees. Thus, forest fragmentation may intensify FSGS, especially for tree species that have a pollination system with low mobility, such as beetle-pollinated trees. Increasing FSGS of tree populations may lead to loss of genetic diversity, high frequency of inbreeding and reduction of regeneration by inbreeding depression. Even for species pollinated by highly mobile bees, such negative effects on regeneration might be unavoidable under logging fragmentation.