Microsatellite analysis of the breeding system and seed dispersal in Shorea leprosula (Dipterocarpaceae)

To understand the breeding system and seed dispersal in Shorea leprosula (D ipterocarpaceae) in Peninsular Malaysia, a microsatellite analysis was cond ucted of embryos of immature and mature fruits fallen in litter traps under the crowns of five trees. Outcrossed and selfed progeny mothered by the tr ees and those dispersed from other trees were distinguished by genotypes of three polymorphic microsatellite loci. The mean outcrossing rate of mature fruit embryos in S. leprosula pollinated by thrips (0.91) was not lower th an those previously reported from Shorea species pollinated by bees, even t hough thrips seem to be less efficient pollinators than bees. Although four of the five trees showed high and stable outcrossing rates during fruit ma turation, the outcrossing rate increased in one tree with highly selfed emb ryos of immature fruits. These results suggest that inbreeding depression d uring fruit maturation as well as self-incompatibility reduce the proportio n of inbred embryos. The proportion of fruits dispersed from neighbor trees in fruits trapped under a tree crown had a mean value of 0.20 and was lowe st under the tree with highly selfed embryos of immature fruits. This low f raction of dispersed fruits under this tree suggests long distances from th is tree to reproductive neighbors, which may reduce cross pollination.