Host specialization and species richness of fruit flies (Diptera: Tephritidae) in a New Guinea rain forest

Frugivorous dacine fruit flies were studied in a lowland tropical rain forest in Papua New Guinea to determine their host specificity, abundance, and the number of species attacking various plant species. Plant species hosted 0-3 fruit fly species at median (1-3 quartile) densities of 1. (0-17) fruit flies per 100 fruits. Fruit flies were mostly specialized to a single plant family (83%, species) and within each family to a single genus (88%) species), while most of the species (66%) were able to feed on > 1. congeneric plant species. Only 30 from the 53 studied plant species were colonized by fruit flies. The plant-fruit fly food web, including these 30 plant species and the total of 29 fruit fly species feeding on them, was divided into 14 compartments, each including 1-8 plant species hosting mutually disjunct assemblages of fruit flies. This structure minimizes indirect interactions among plant species via shared herbivores. The local species pool was estimated at 152 132 ( SE) fruit fly species. Forty per cent of all taxonomically described species known from Papua New Guinea were reared or trapped in our study area. Such a high proportion indicates low beta-diversity of fruit flies. Steiner traps were highly efficient in sampling the lure-responsive fruit fly species as they re-collected 84% of all species trapped in the same area 5 y before. Fruit fly monitoring by these traps is a cheap, simple and efficient method for the study of spatial and temporal changes in rain-forest communities.