AN ANALYSIS OF DIET SPECIALIZATION IN FRUGIVOROUS PTEROPUS-POLIOCEPHALUS (MEGACHIROPTERA) IN AUSTRALIAN SUBTROPICAL RAIN-FOREST

The Grey-headed flying fox Pteropus poliocephalus Temminck 1825 is the only mammalian frugivore to occupy substantial areas of the subtropic al rainforests of eastern Australia. The composition of the P. polioce phalus diet and diet specialization in the species are therefore perti nent to studies of trophic structure, seed dispersal and evolutionary processes in these forests. During a three-year diet study, P. polioce phalus used fruits from 44 species of canopy and edge plants. Their ta xonomically diverse diet was dominated by the Myrtaceae and Moraceae. Dietary specialization by P. poliocephalus was examined using two crit eria: the influence of fruit morphology on diet choice and dietary ove rlap with sympatric avian frugivores. There was no evidence from eithe r approach that they were specialist feeders. Initial analyses compari ng the morphological characters of diet fruits with fruits available t o P. paliocephalus during the study period showed a preference for whi te fruits, berries, syconia and fruits with multiple seeds, and avoida nce of black fruits and drupes. However, these significant results wer e not sustained when the confounding effects of correlations between f ruit morphology and other traits were considered. All, except the resp onse to berries, could be attributed to either avoidance by I? polioce phalus of secondary compounds in the Lauraceae or selection for the be neficial phenology of Ficus. Dietary overlap with frugivorous birds wa s notably high and the fruit diet of P. poliocephalus formed a subset of the avian diet. Associations between fruit colour, size and protect ive mechanisms have been documented in other rainforest areas and have been proposed as indicators of coadaptive relationships between verte brate frugivores and their diet plants. However, these associations we re 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.