An experimental test of Dodson's hypothesis that Ambystoma (a salamander) and Chaoborus (a phantom midge) have complementary feeding niches

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Abstract
The removal from an alpine pond of eggs of the salamander Ambystoma gracile had a large impact on the zooplankton community. The pond was dominated by the large Daphnia rosea, while a nearby pond, from which salamander eggs were not removed, was dominated by the small Diaphanosoma brachyurum. Chaoborus trivittatus crop content analyses revealed that in the experimental pond, food intake of second and third instars was low. In the fall, fourth instars were scarce and their dry weight was 50% lower than those in the previous year or those of the control pond.When larval Ambystoma is abundant, it preys heavily upon the cladocerans Holopedium gibberum and Daphnia, which are too large for Chaoborus to eat. Whereas Holopedium appears not to be much affected by the intensity of Ambystoma predation, the reduction in density of Daphnia leads to increased density of Diaphanosoma, possibly because of reduced competitive interaction. Diaphanosoma is the main food source, when available, of second and third instar Chaoborus. In this indirect way, Chaoborus depends on vertebrate predation to reach successfully its fourth instar. This lends support to Dodson's hypothesis of complementary feeding niches.

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