Conventional and genetic measures of seed dispersal for Dipteryx panamensis (Fabaceae) in continuous and fragmented Costa Rican rain forest

Abstract

The effects of habitat fragmentation on seed dispersal can strongly influence the evolutionary potential of tropical forest plant communities. Few studies have combined traditional methods and molecular tools for the analysis of dispersal in fragmented landscapes. Here seed dispersal distances were documented for the tree Dipteryx panamensis in continuous forest and two forest fragments in Costa Rica, Central America. Distance matrices were calculated between adult trees (n = 283) and the locations of seeds (n = 3016) encountered along 100 × 4-m transects (n = 77). There was no significant difference in the density of seeds dispersed > 25 m from the nearest adult (n = 253) among sites. There was a strong correlation between the locations of dispersed seeds and the locations of overstorey palms favoured as bat feeding roosts in continuous forest and both fragments. Exact dispersal distances were determined for a subset of seeds (n = 14) from which maternal endocarp DNA could be extracted and matched to maternal trees using microsatellite analysis. Dispersal within fragments and from pasture trees into adjacent fragments was documented, at a maximum distance of 853 m. Results show no evidence of a fragmentation effect on D. panamensis seed dispersal in this landscape and strongly suggest bat-mediated dispersal at all sites.