Evolution of diversity: Pattern formation in phenotype space

Understanding the origin of diversity is one of the fundamental conceptual problems in biology. Traditional evolutionary theory predicts uniformity: natural selection acting on organisms under given environmental conditions and developmental constraints produces a unique, optimally adapted phenotype. According to this view, different types only come about through a change in conditions over space or time. In particular, the process of diversification, that is, the split of an ancestral population into distinct descendent lineages, is a by-product of geographical separation. This traditional view misses out on the important perspective that diversification itself can be an adaptive process triggered by ecological interactions within an ancestral population. In this perspective, diversification is a process of pattern formation in phenotype space, during which frequency-dependent selection splits unimodal phenotype distributions into multimodal distributions, with the different modes corresponding to different descending species. In this talk I will review recent theoretical work on adaptive diversification from the general perspective of pattern formation. I will start out showing how diversity can evolve in the framework of adaptive dynamics due to the phenomenon of evolutionary branching. I will then consider PDE models of continuous phenotype distributions, showing that speciation due to pattern formation is a plausible outcome in such models. Finally, I will briefly introduce a general framework for understanding pattern formation in PDE models that is based on equivariant bifurcation theory.

Refreshments will be served at 2:45 p.m. (Lounge, MATX 1115).