Since plant population often forms local genetic structure where close plants tend to share the same neutral and adaptive genes, pollen and seed dispersal distance may affect offspring fitness through inbreeding depression and home-site advantage where genes from the same habitats are advantageous for local adaptation.

We investigated the effects of pollen and seed dispersal distance on seedling fitness of Dipterocarpus tempehes in Lambir Hills National Park, Sarawak, Malaysia. The population in 70-ha study site was divided into four subpopulations separated by ridges. Seedlings were transplanted within and among the subpopulations and their survival and growth monitored for 20 months. Pollen and seed dispersal distances were determined by parentage analysis using 10 DNA microsatellite.

Data showed inbreeding depression within subpopulation in seedling growth. However, when both pollens and seeds were dispersed within-subpopulations, seedlings showed faster growth. The result clearly indicate the home-site advantage, that could be explained by outbreeding depression and the local adaptation. The finding that home-site advantage occurs in such a small spatial scale may facilitate our understanding to generation and maintenance of tropical species diversity.