A community of frugivorous insects was studied by rearing of 25565 individual insects representing three orders (Coleoptera, Lepidoptera and Diptera except Drosophilidae) from 326 woody plant species in a lowland rainforest in Papua New Guinea. Fruits from 19.3% of plant species were not attacked by any insect order, 33.4% of plant species were attacked by a single order, 30% by two orders and 17.2% by all three orders. The likelihood of attack by individual orders was positively correlated so that a higher proportion of plant species than expected suffered either no attack at all or was attacked by all three insect orders. Fruits from most of the plant species exhibited low rates of attack and low densities of insects. One kilogram of fruit was attacked on average by 11 insects, including three to four Coleoptera, six Diptera and one Lepidoptera. Thus, we reared on average one insect from 10 fruits, including one Diptera from 14 fruits, one Coleoptera from 22 fruits and one Lepidoptera from 100 fruits. Only 72 out of the 326 plant species hosted more than one insect per 10 fruits, and only seven species supported a density of greater than one insect per fruit. Our results suggest that specialized insect seed predators are probably too rare to maintain the diversity of vegetation by density-dependent mortality of seeds as suggested by the Janzen-Connell hypothesis. Fruit weight, fruit volume, mesocarp volume, seed volume and fleshiness had no significant effect on the probability that a fruit would be attacked by an insect frugivore. However, fruits attacked by Diptera were significantly larger and had larger volume of both mesocarp and seeds than fruits attacked by Coleoptera and Lepidoptera.
Bibliographical noteFunding Information:
The present study, as many others in the past 25 years, has benefitted from Roger Kitching?s ideas on food webs and from his ecological studies in PNGand elsewhere, as well as from the inspirational and stimulating milieu always prevailing in his lab. This study was undertaken with the support of the PNG National Agriculture Research Institute, PNG Forest Research Institute and PNG Department of Environment and Conservation. We thank New Guinea Research Binatang Center staff and field assistants from Wanang, Ohu and Baitabag villages for technical assistance. Weevil identifications were assisted by Alexander Riedel, Richard Thompson (Baridinae) and Marek Wanat (Apionidae). Fly taxonomy was assisted by Miroslav Bartak (Neriidae), Stepan Kubik (Chloropidae), Rudolf Rozkosny (Stratiomyidae) and Andrew Wittington (Syrphidae). Moth taxonomy was assisted by John Brown (Tortricidae), Don Davis (Tineidae), Lauren Helgen, Jeremy Holloway, Marianne Horak (Phycitinae and Tortricidae), Margaret Rosati, Kevin Tuck (Tortricidae) and Maia Vaswani. We appreciate access to the vital collections of the Natural History Museum, London. Plant taxonomy was assisted by Kipiro Damas and KennethMolem. This study was supported by the Czech Science Foundation (13-09979S), Darwin Initiative for the Survival of Species (UK), the Christensen Fund and the US National Science Foundation (DEB-0515678 and DEB816749). We thank Paul Hebert and colleagues at the Biodiversity Institute of Ontario for their assistance with the barcode library of the local fauna, which was funded by the Government of Canada through Genome Canada and the Ontario Genomics Institute (2008?0GIICI-03).
- Seed predation
- Seed-eating herbivore