Genetic and Environmental Basis of the Phenotypic Divergence in Locomotion-Related Traits Between Two Lake Whitefish Species (Coregonus clupeaformis)

Phenotypic divergence between populations occupying different ecological niches can result from phenotypic plasticity, genetic divergence, or a combination of both. Phenotypic plasticity is defined as the ability of a single genotype to modify a trait in response to an environmental change and it is likely to be an important process underlying rapid acclimation during lifetime. On the other hand, genetic divergence is the result of an inter-generational evolutionary process that occurs at the population level. The goal of this study was to assess the relative role of phenotypic plasticity, genetic divergence and their interactions in explaining the extent of phenotypic divergence inside the lake whitefish species (Coregonus clupeaformis) complex. For this purpose, cross-experiment with two different water-velocities was performed to simulate the different swimming demands that facing the two species in wild. Measurements were taken on many traits including whole body shape, heart and percentage of red muscle. The results point out an important role of genetic divergence with little impact of environment. The phenotypic difference also appears to be conformed to functional expectation in several cases (e.g.: slender body observed in the more swimming demanding niche). Altogether, the results suggest an adaptive phenotypic divergence of locomotion-related traits in lake whitefish species complex.