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Abstract

Phenotypic plasticity, the property of a genotype to form distinct phenotypes in response to the environment, is increasingly recognized as major facilitator of evolutionary novelty and evolutionary diversification, although it was largely ignored in the Neo-Darwinian Synthesis in the 1930ies and 1940ies. Mary Jane West-Eberhard was among the first to recognize the importance of phenotypic plasticity and her 2003 monograph provided a solid theoretical foundation for plasticity and its role in evolution. Her theoretical contribution built on comparative studies on solitary hunting and social wasps and more generally, the significance of alternative phenotypes. I will review these theoretical aspects of phenotypic plasticity and the facilitation hypothesis before moving to a comprehensive case study – mouth-form plasticity in nematodes. My laboratory studies the free-living nematode Pristionchus pacificus, which we have established as model organism for integrative studies in evolutionary biology, by working at the interphase of developmental genetics, evo-devo, population genetics and ecology. P. pacificus is a potential predator of other nematodes, a novel behavioral trait that builds on the formation of a novel morphological structure, the formation of teeth-like denticles. These teeth occur in form of a dimorphism, an example of developmental plasticity that allows mechanistic insight. I will summarize our current understanding of the genetics and epigenetics of mouth-form regulation and will show how transgenerational effects and genetic assimilation can eventually result in evolutionary novelty.