Inter- and intraspecific differences in Daphnia life histories in response to two resources: The green alga Scenedesmus and the filamentous cyanobacterium Oscillatoria

Abstract

The effects of two food sources on life history traits of Daphnia galeata, Daphnia cucullata and their interspecific hybrid. D. cucullata x galeata, were studied. For each taxon, two clones were reared on both a green alga (Scenedesmus obliguus and a filamentous cyanobacterium (Oscillatoria limnetica). Reproduction on Oscillatoria was generally lower than on Scenedesmus, but a positive population growth rate was still achieved, except in one hybrid clone. Life history traits showed differences among the intraspecific clones. Daphnia cucullata, the smallest of the three taxa, was the best of the three utilizing Oscillatoria as food. But D. galeata and the hybrid did not differ clearly. The clones within the taxa also differed in the extent they could utilized Oscillatoria as food. The results are discussed in relation to the co-existence of these taxa in nature.