Comparing the Dispersal of Large-seeded Tree Species by Frugivore Assemblages in Tropical Montane Forest in Africa

摘要

We examined frugivore visitation and seed dispersal of five large-seeded (greater-than-or-equal 5 mm) tree species in tropical montane forest based on their occurrence in frugivorous primate diets: Ekebergia capensis, Olea capensis, Parinari excelsa, Prunus africana, and Syzygium guineense. A total of 21 frugivores in five assemblages (i.e., chimpanzees, cercopithecines, large-bodied birds, small-bodied birds, and squirrels) were observed over the study period (August 2006 and October-April 2007). We observed seed dispersal in four of five tree species studied; no dispersal was observed for P. excelsa. Frugivore assemblages did not visit tree species equally. Primates spent the most time in trees and had the largest group size. Large-bodied birds (LB) and chimpanzees dispersed the highest number of seeds per minute. LB and cercopithecines potentially dispersed the greatest number of seeds for E. capensis, and chimpanzees for S. guineense. Our analyses indicated that the mean fruiting duration of the focal tree, time in the tree, and number of species present are important predictor variables for seed dispersal by small- and large-bodied birds, and cercopithecines. The number of fruiting trees in the immediate vicinity of the focal tree further predicted seed dispersal for small-bodied birds (SB). Large-bodied birdseed dispersal also was predicted by time in tree by SB, and the number of individuals for SB and cercopithecines. Cercopithecines (CS) were further explained by the time in tree and number of species (SB & LB), and number of individuals for CS. Our study highlights the complexity of describing the relative importance of a frugivore assemblage to the dispersal of a tree species seeds.