Investigating the relative importance of parentage versus environmental factors on heterochrony in basommatophoran freshwater snails

Abstract

The importance of genetics in inter-specific heterochrony is long known; however, intra-specific heterochrony was believed to be driven by environmental variation. Recent studies on Radix balthica showed higher similarity in developmental timing across generations in genetically similar embryos than in distantly related individuals. In the present study, the relative importance of parentage and egg-mass origin is compared with the environmental importance in generating the heterochrony in Radix balthica. Six developmental events were recorded daily. The analysis of the variations showed that parentage influencing variation in developmental timing to be more important than environmental conditions. Only hatching was affected by the environment as well as parentage. When comparing the sequence of developmental events, a strong link was found between treatments showing sequence variation and nil mortality in the same treatment. This was found between parents and between egg-masses from a single parent. This study shows that timing of developmental events is influenced by parentage whereas the sequence of developmental events is influenced by treatment. These findings indicate that both genetics and environmental plasticity influences intra-specific heterochrony but in different ways.