Quantitative Genetic Studies of Diapause in Daphnia: Genetic and Environmental Control and Genetic Consequences
Findings suggest that diapausing eggs in cyclical parthenogenetic Daphnia populations are produced by sexual reproduction and means and genetic variances for life history traits change significantly upon SR in the opposite direction to that promoted by the previous selection.
Abstract
Diapausing eggs (ephippia) in cyclical parthenogenetic Daphnia populations are produced by sexual reproduction(SR). A series of experiments were performed in different populations and species of Daphnia to investigate: 1) genetic and environmental controls of SR and revival of diapausing eggs; 2) the photoperiodic responses of SR in closely related species inhabiting overlapping but different micro habitats; 3) the genetic consequences of SR on populations' genetic architecture (genotypic mean and genetic variance of life history traits). The main findings are: 1) Genetic and environmental effects, and G*E interaction all have significant effects on SR and hatching of resting eggs. Significant G*E interaction may help maintain the high genetic variation for SR observed within environments; 2) Photoperiodic responses of SR are distinct in closely related species inhabiting overlapping but different micro habitats. This contributes to further differentiate closely related Daphnia species and is likely to be an example of allotropic speciation in aquatic systems; 3) Means and genetic variances for life history traits change significantly upon SR in the opposite direction to that promoted by the previous selection (genetic slippage). This causes temporary maladaptation (genetic slippage and release of hidden genetic variance), which must have been compensated by the evolutionary advantage of diapause.