Reproductive strategies in the freshwater sphaeriid clam,Musculium partumeium (say), from a permanent and a temporary pond.

Reproduction was studied in two populations ofMusculium partumeium from temporary and permanent ponds. Adults of the single annual generation from the ephemeral pond have an annual selection ratio of 25:1 with 37.03 μgC per newborn, and an intrinsic rate of increase (r) of 0.0084 day-1. Fall-born adults from the permanent pond have an annual selection ratio of 38:1, 21.82 μgC per newborn and anr of 0.0115 day-1; springborn adults have an annual selection ratio of 136:1 (107:1 for their contribution to fall birth and 29:1 for the spring birth period) with newborns of 24.21 μgC and anr of 0.0304. The trade off between quantity and quality of young is discussed in terms of adaptive strategies.