Life-history variation related to the first adult instar in daphnids derived from diapausing and subitaneous eggs

Using a life-table approach, pairs of exephippial sibs of Daphnia pulex were surveyed for sources of variation in life-history traits, and daphnids derived from diapausing and subitaneous eggs were assessed for differences in variance for these traits. Significant variation due to initial body length and sibs pair effect was observed in traits of exephippial females at the first adult instar (FAI). These results suggest higher environmental and genetic variability of life-history traits at the FAI in daphnids hatching from diapausing eggs than that in parthenogenetically derived ones. Exephippial females exhibited significantly higher variation in life-history properties at the FAI in response to various food levels, as well as within a high food treatment. The largest difference was found for the size of the first clutch and the body length of the juveniles produced in this clutch. Variance for relative fitness in females emerging from diapause was also higher than that for ones derived from subitaneous eggs. Life-history strategies in exephippial Daphnia hatching during the early season are adapted to optimal conditions, whereas individuals of another origin are adapted to more unpredictable environments, and demonstrate bet-hedging strategies.[PUBLICATION ABSTRACT]