Abstract
Phenotypic plasticity is a key determinant of organismal performance, allowing rapid adjustment to environmental variation. However, its evolutionary impact is in dispute. On the one hand, plasticity facilitates range expansion and thereby increases the opportunity for evolutionary differentiation. On the other hand, plastic responses will weaken selection for genetic change, hampering adaptive evolution. We currently lack the empirical data to verify either scenario, limiting our ability to predict how biodiversity responds to environmental change. Here, we aim to resolve this ambiguity by determining the role of visual plasticity in the evolution of cichlid fish species diversity. Colour vision has a relatively simple genetic basis, exhibits plasticity, affects both reproduction and survival, and is often associated with species divergence. The species-rich cichlid family provides a well-resolved comparative framework. Focusing on the African cichlids (600+ species), we will quantify plasticity by 1) documenting visual niche breadth in nature and 2) measuring environment-induced changes in visual gene expression in the laboratory. We then use phylogenetic analysis to test whether more plastic lineages are more species-rich than less plastic ones. Subsequently, we experimentally address the underlying mechanism by quantifying the effects of visual plasticity on individual behaviour and fitness. This will establish the causal relationship between visual plasticity and ecological niche expansion. Together, these approaches will reveal whether and how visual plasticity can promote or inhibit speciation. By integrating developmental genetics and evolutionary ecology, this project will generate fundamental insights into the contribution of plasticity to biodiversity dynamics in a changing world.
Netherlands