Habitat disorder: an ecological measure to predict Daphnia sexual reproduction in stochastic environments

The aim of the present research is to study two cyclic parthenogenetic populations of Daphnia obtusa, occurring in distinct but geographically overlapping ponds. In both populations parthenogenetic eggs were laid continuously throughout the year, showing the typical pattern observed at our latitudes, with two peaks of production in winter and in early spring. On the contrary, the maximum production of resting eggs was not simultaneous in the two biotopes and coincided with the winter peak in one pond and with the spring peak in the other one. To explain this different behaviour, we considered a set of biotic and abiotic factors characteristic of the habitats under study, and found evidences of a link between the annual production of resting eggs and increasing environmental variation