Abstract

Integrative evolutionary biology: a need for interdisciplinary studies of development, ecology and population genetics

Life on Earth shows an astonishing diversity of form and phenotype. But our understanding of how this diversity was generated as a result of historical processes is still limited. We use a highly interdisciplinary approach that integrates development, evo-devo, ecology and population genetics to unravel the mechanistic changes that give rise to evolutionary alterations and novelty. For this to be achieved well-selected model organisms with a sophisticated analytical toolkit for functional investigations have to be developed. We established the free-living nematode Pristionchus pacificus as a model system in evolutionary biology. P. pacificus allows in a unique manner to combine laboratory studies building on genetic, genomic and transgenic tools with field work in ecology and population genetics. Detailed investigations of vulva formation revealed that developmental mechanisms differ strongly between the model organisms C. elegans and P. pacificus. I will describe our work on vulva development, providing an example for developmental system drift. While evo-devo results in fundamental insight into the evolution of developmental mechanisms, it also necessitates a synthesis with other areas of evolutionary biology: Synthesis with “population genetics” can reveal how phenotypic evolution is initiated at the micro-evolutionary level and synthesis with “evolutionary ecology” can add an ecological perspective to these evolutionary processes. P. pacificus has a well-defined ecological association with scarab beetles that we have investigated in great detail. More than 500 strains of P. pacificus have been isolated from around the world. In the last few years, our biogeographic work focused on La Réunion, a young volcanic island in the Indian Ocean that harbours the complete worldwide genetic diversity of P. pacificus due to independent invasions of this nematode with different carrier beetles. Thus, La Réunion represents a microscosm for studies of population genetic and ecology. In this context, I will report from our most recent work focusing on the evolution of morphological novelty. P. pacificus forms teeth-like denticles involved in predatory feeding on fungi and other nematode species. We are studying the regulation of this mouth form dimorphism, combining genetic studies with natural variation and macroevolution. I will describe a master switch gene of teeth regulation that couples microevolution and macroevolution. These case studies will highlight the importance of integrative approaches in modern evolutionary biology.