Resource partitioning among larvae of six coexisting odonate species of the Kali Gandaki River, central Nepal (Anisoptera)

Odon. larvae were collected from 50-1190 m elevation in central Nepal’s Gandaki River from 1984 to 1986. Resource partitioning among coexisting odon. spp. at high (>500m) and low (<500m) elevations was investigated by examining their gut contents. At both elevations, diet differences between Anisogomphus occipitalis and Davidius sp. were statistically significant. A. occipitalis ate mostly midges whereas Davidius sp. ate mayflies and caddisflies as well as midges. At low elevation there was no diet difference between A. occipitalis and Paragomphus lineatus nor between the libellulids Crocothemis servilia and Trithemis festiva. Analyses of niche breadths indicate overlap between Davidius sp., Macromia moorei, C. servilia, and T. festiva, and between A. occipitalis and P. lineatus. Significant diet differences in both A. occipitalis and Davidius sp. between low and high elevations may indicate negative interactions in the presence of other coexisting species at low elevation. Similarly, at low elevation both spp. have a narrow niche breadth, a low average number of prey items per gut, and also more empty guts than at high elevation. Mean body weights of studied odon. were relatively higher at lower elevation than at higher elevation. Predatory interactions seemed to be of little or no importance in structuring this lotic odon. assemblage, in contrast with lentic Odonata in other studies.