Modeling coregonid fish diversification along a vertical gradient in water temperature
In most existing models of adaptive speciation, ecological specialization via resource partitioning is the predominant driving force for the evolution of reproductive isolation. One conclusion from these theoretical studies is that adaptive speciation is a theoretically plausible process, especially along environmental gradients. However, empirically motivated and data-based speciation models including ecologically derived parameter assumptions are needed to better evaluate the potential for such processes to occur in nature. Freshwater fish occupying postglacial environments are commonly used model systems for studying adaptive diversification in evolutionary ecology. Several taxa of freshwater fish have generated species and ecological diversity in a manner consistent with the theory of adaptive speciation. Specifically, there is increasing evidence that ecological opportunity and competition for resources promote adaptive divergence in coregonid fish, which feature sympatric forms of phenotypically divergent and reproductively isolated populations throughout the northern hemisphere. A sympatric pair of coregonids exists also in the northern German Lake Stechlin. Here, evidence suggests that the two existing species have segregated along the temperature-depth gradient in terms of divergent metabolic temperature adaptations. The goal of this research project is to develop a model for this ecological diversification as a first step towards understanding the adaptive speciation of fish populations along the environmental gradient of water temperature. We will start with a spatially structured single-trait model under the adaptive dynamics assumptions of asexual reproduction with small and rare mutations. If time allows, we will extend the model to size-structured and/or sexually reproducing populations.