Offspring development and life-history variation in a water flea depends upon clone-specific integration of genetic, non-genetic and environmental cues

Abstract

Theory predicts that offspring developmental strategies involve the integration of genetic, non-genetic and environmental ‘cues’. But it is unclear how cue integration is achieved during development, and whether this pattern is general or genotype specific. In order to test this, we manipulated the maternal and offspring environments of three genetically distinct clones of the water flea Daphnia magna taken from different populations. We then quantified the effect that the genotype, maternal environment and the offspring environment had on the development and life histories of the three different clones. Mothers responded to the same maternal environments in different ways, resulting in clone-specific maternal effects on neonate size. Offspring responses to maternal cues varied according to the trait in question and were also clone specific. The integration of these maternal effects during development was highly context dependent in two clones but more consistent across environments in the third. Genetic, non-genetic and environmental cues contributed to offspring phenotypic variation in all three clones, but there was no general pattern linking traits to specific cues. In fact, two clones used different combinations of cues at different points in development to achieve similar phenotypic outcomes. Reaction norms for the age and size at which maturation was initiated differed among genotypes, between maternal environments and across current environments. Developmental transitions such as the decision to mature may thus play an important role in determining patterns of cue integration. Considering multiple traits during development demonstrated that variation in the integration of genetic, non-genetic and environmental cues was an important determinant of life-history variation among D. magna genotypes. This variation is likely to influence phenotypic evolution. A lay summary is available for this article.