SREL Reprint #1802

Patterns of offspring size at birth in clonal and sexual strains of Poeciliopsis (Poeciliidae)

Stephen C. Weeks1 and Oscar E. Gaggiotti2

1University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802
2Center for Theoreticial and Applied Genetics, P.O. Box 231, Cook College, Rutgers University, New Brunswick, New Jersey 08903

Abstract: Females from two closely related reproductive complexes of Poeciliopsis reared under common conditions differed in weight of offspring at birth. The two fish strains from a more variable, upstream environment had significantly larger offspring than did three downstream fish strains. There was no consistent pattern of within-clutch variation for the two reproductive complexes. We interpret these data by examining the biotic and abiotic environmental factors in the natural habitats of these two reproductive complexes that may affect offspring size at birth and relate these observations to current adaptive explanations for differences in offspring size. Larger offspring were significantly less likely to be cannibalized by adult Poeciliopsis. Cannibalism, combined with the possibility of size-selective predation by insect predators in the upstream habitat, might lead to an advantage of producing larger offspring in these streams. No trends between these two reproductive complexes were found in within-clutch variation in offspring size consistent with predictions of "bet-hedging" life-history models.

SREL Reprint #1802

Weeks, S.C. and O.E. Gaggiotti. 1993. Patterns of offspring size at birth in clonal and sexual strains of Poeciliopsis (Poeciliidae). Copeia 1993:1003-1009.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).