DISTRIBUTION OF CRUSTACEAN DIAPAUSE - MICROEVOLUTIONARY AND MACROEVOLUTIONARY PATTERN AND PROCESS

Theoretical predictions for the relationships between duration of dorm ancy, reproductive life span, and dispersal ability developed for plan ts in temporally varying environments are applied here to crustaceans. Mathematical models suggest that diapause duration should negatively covary with adult life span, and that both diapause and life span shou ld negatively covary with dispersal ability. A survey of 167 crustacea n species from 20 orders and three classes confirms that species with prolonged diapause have short adult life spans and those with long adu lt lives either have diapause lasting less than a year, or do not diap ause at all. Prolonged diapause is more common among small or inland w ater crustaceans than it is among large or marine species, whereas lar ge or marine species have significantly longer adult life spans on ave rage than do those that are small or from inland waters. A greater fra ction of species in the Branchiopoda exhibit prolonged diapause than d o members of the Maxillopoda which, in turn, are more likely to exhibi t prolonged diapause than are the Malacostraca. A greater fraction of malacostracan species have adult life spans exceeding one year than do species in either the Branchiopoda or the Maxillopoda. Cladistic anal ysis shows that phylogenetic constraint is likely to be at least in pa rt responsible for the expression of diapause among the Crustacea. We conclude that both natural selection and macroevolutionary pattern hav e influenced the distribution of diapause among modern crustaceans.