Dietary differences between two co-occurring calanoid copepod species.

Two co-occurring high altitude calanoid copepods, Diaptomus shoshone Marsh and D. coloradensis Forbes are of different size: the former is approximately twice as long as the latter. There are also temporal differences in development: the former matures 2-3 weeks before the latter in most ponds. Gut analyses of copepodids and adults of both species indicate that D. shoshone eats larger food particles but that D. shoshone early copepodids eat particles similar in size to D. coloradensis adults. Morphology of feeding appendages partially explains the dietary differences. These data are discussed from the viewpoint of competition between the species; it is concluded that either temporal differences or size differences of copepodids and adults would allow coexistence and that extreme size differences are probably unimportant compared to morphological differences of feeding appendages and perhaps behavioral differences.