The frugivore community and the fruiting plant flora in a New Guinea rainforest: Identifying keystone frugivores

Abstract

The flora at Crater Mountain Biological Research Station in Papua New Guinea is very diverse: 228 tree species (10 cm DBH) on a single hectare. However, the vertebrate fauna (169 bird and 31 mammal species) is less diverse than many tropical sites. At least 47% of bird species and 29% of mammal species are partially frugivorous. Using data on relative abundance, mass, and degree of frugivory for all frugivorous vertebrates at Crater, we generated a crude index of importance for each species. Using the fruit size and mass data from 400 plant species, we exclude fruits either too large or too heavy for each frugivore to disperse, yielding a possible diet for each species. Four species (a cassowary, a hornbill, a h fruit pigeon and a flying fox) stand out as being crucial dispersers for a large subset of the plant community. The frugivore with the highest importance ranking, Casuarius bennetti, is highly effective as a disperser. Cassowaries appear to be a keystone frugivore, especially for large-fruited plant species (67 species > 50 g at our study site). The method employed is fairly simple and quickly identifies candidates for keystone frugivore status. However, further life history studies are recommended for confirmation of f importance when using this method.