Microsatellite Analysis of the Breeding System and Seed Dispersal in Shorea leprosula (Dipterocarpaceae)

Abstract

To understand the breeding system and seed dispersal in Shorea leprosula (Dipterocarpaceae) in Peninsular Malaysia, a microsatellite analysis was conducted of embryos of immature and mature fruits fallen in litter traps under the crowns of five trees. Outcrossed and selfed progeny mothered by the trees 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 than those previously reported from Shorea species pollinated by bees, even though thrips seem to be less efficient pollinators than bees. Although four of the five trees showed high and stable outcrossing rates during fruit maturation, the outcrossing rate increased in one tree with highly selfed embryos of immature fruits. These results suggest that inbreeding depression during fruit maturation as well as self‐incompatibility reduce the proportion 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 lowest under the tree with highly selfed embryos of immature fruits. This low fraction of dispersed fruits under this tree suggests long distances from this tree to reproductive neighbors, which may reduce cross pollination.