Odonate Guild Composition: Experiments with Colonization History and Fish Predation

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Abstract
Fewer than half of the anisopteran odonate species that oviposited in a North Carolina farm pond successfully metamorphosed from that pond. Odonates metamorphosed during two periods: early April though early June, and late May through early September. I used an experiment designed for variance analysis to measure the impact of fish and early—breeding odonates on the abundance and species composition of late—breeding odonates. Odonates recruited naturally in open—topped screened pens that either excluded or contained fish. I placed pens in the pond either during or after the early species breeding season to alter the abundance of larval early breeders. Fish exclusion increased the combined abundances of all anisopteran species 5—10 times above abundances in pens containing fish. However, fish also facilitated the recruitment of one species, Perithemis tenera. Placement of fish exclusion pens in late June instead of early May reduced abundance of early breeders and increased abundances of two late breeders, Perithemis tenera and Pachydiplax longipennis. Early—breeders did not reduce late—breeder recruitment in pens with fish. Abundances of early and late breeders were significantly negatively correlated in pens without fish, but abundances of the same species were not significantly correlated in pens with fish. Different histories of colonization by early breeders influenced interspecific interactions among odonates only if fish were absent. Most variation in the composition of experimental communities was explained by a hierarchy of negative effects of fish on odonate abundance, and negative effects of early—breeders on late—breeders in the absence of fish.