Male fecundity and pollen dispersal in hill dipterocarps: significance of mass synchronized flowering and implications for conservation.

摘要

To understand pollinator-plant symbioses and to conserve forest resources effectively, we need an understanding of pollen dispersal patterns and the heterogeneity (spatial and temporal) of male fecundity. We investigated pollen dispersal patterns of the hill dipterocarp species Shorea curtisii using a modified Neighbourhood model. Seeds were collected following a sporadic general flowering (GF) event in 2002 and two mass GF events in 1998 and 2005. Seed paternity was then determined to investigate pollen dispersal patterns and the heterogeneity of male fecundity. Pollen dispersal distances were longer, and the effective number of males lower, in the sporadic GF of 2002, than in the mass GF events of 1998 and 2005. There was high between-individual variation in male fecundity, and small trees contributed less than large trees to the analysed seed pool. The results indicate that selective logging may adversely affect the reproduction of such species due to the removal of large trees from the reproductive population. Synthesis. The large number of effective male individuals during the mass GF events provides evidence of Allee effects, suggesting that the mass GF events are of evolutionary significance and may contribute to the maintenance of genetic diversity. Future forestry practice needs to take into account variation in male fecundity, pollen dispersal and the mating system to ensure sustainable regeneration.