Seasonal Variation in the Intensity of Competition and Predation Among Dragonfly Larvae

摘要: In nature, both similar and disparate sizes of Libellula lydia L. luctuosa larvae frequently co-occur in time space. To determine if these interact as competitors, and/or predators prey, I used artificial ponds to manipulate density, species composition, size range co-occurring larvae. Detailed life history data were design separate fall spring experiments. experiments, "competition treatments" contained only size, whereas "predation con- tained size. competition treatments there no density-dependent growth responses. How- ever, the experiment, grew significantly faster low density than high treatments. This seasonal difference was attributed fluctuations resource abundance. Competition did not directly affect survivorship. predation treatments, mortality higher it Inter-odonate accounted for 25-45% total larval fall, but 10-15% spring. absence inter-odonate predation, lower larger smaller larvae, suggesting latter are more susceptible by other invertebrate predators. Thus, competition, de- creasing rates, should indirectly These provide evidence that will simultaneously coexistence between two dragonfly species. Predation early development ameliorate intensity subsequent competitive interactions at a when resources most likely be limiting. type mixed competition/predation inter- action is analogous predator-mediated coexistence, might explain how such eco- logically can coexist densities.