| Abstract: | Abstract The Grey-headed flying fox Pteropus poliocephalus Temminck 1825 is the only mammalian frugivore to occupy substantial areas of the subtropical rainforests of eastern Australia. The composition of the P. poliocephalus diet and diet specialization in the species are therefore pertinent to studies of trophic structure, seed dispersal and evolutionary processes in these forests. During a three-year diet study, P. poliocephalus used fruits from 44 species of canopy and edge plants. Their taxonomically diverse diet was dominated by the Myrtaceae and Moraceae. Dietary specialization by P. poliocephalus was examined using two criteria: the influence of fruit morphology on diet choice and dietary overlap with sympatric avian frugivores. There was no evidence from either approach that they were specialist feeders. Initial analyses comparing the morphological characters of diet fruits with fruits available to P. poliocephalus during the study period showed a preference for white fruits, berries, syconia and fruits with multiple seeds, and avoidance of black fruits and drupes. However, these significant results were not sustained when the confounding effects of correlations between fruit morphology and other traits were considered. All, except the response to berries, could be attributed to either avoidance by P. poliocephalus of secondary compounds in the Lauraceae or selection for the beneficial phenology of Ficus. Dietary overlap with frugivorous birds was notably high and the fruit diet of P. poliocephalus formed a subset of the avian diet. Associations between fruit colour, size and protective mechanisms have been documented in other rainforest areas and have been proposed as indicators of coadaptive relationships between vertebrate frugivores and their diet plants. However, these associations were not apparent in the morphological characters of fleshy fruits from Australian subtropical rainforest trees. An explanatory hypothesis of primarily avian influence on fruit traits is presented. |
