Genetic and environmental factors influence survival and hatching of diapausing eggs

To test the hypothesis that variation in hatching and survival of Daphnia dormant eggs is fostered by genetic differences among populations, rather than system-specific availability of environmental cues, I measured hatching and egg survival rates for Daphnia from 22 shallow, fishless ponds in the midwestern U.S.A. Although all eggs were incubated at a water depth of 0.75 m or less in their natal pond, hatching rates varied between 5% and 90% and survival rates of eggs remaining in the egg bank ranged from 7% to 72%. There was no significant relationship between hatching and environmental cues such as light, oxygen content, or conductivity, although a negative relationship with depth was observed. Reciprocal transplant experiments quantified genetic and environmental influences on dormancy and survival, revealing strong population-by-host environment interactions. Thus, plasticity to environmental cues and genetic or maternal effects likely interact to determine hatching and survival rates in the field.