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Zusammenfassung:
The aim of this research project is to study the evolutionary and ecological role of phenotypic plasticity, as well as its genetic basis. Nematodes of the genus Pristiochus show a variable ecology: they can be found as soil-dwelling animals or in necronimic association with scarab beetles. They show a dimorphism in their mouth form, where stenostomatous and eurystomatous worms have qualitative as well as quantitative differences. This dimorphism is thought to be of great ecological relevance since it underlies different feeding strategies. Using selection inbred lines we have shown that this dimorphism is a case of phenotypic plasticity. In addition, we are able to manipulate the reaction norm by changing the laboratory environment: starving the worms in their early larval development (until the J2 larval stage) causes a dramatic increase in the ratio of eurystomatous worms in all tested strains of Pristionchus pacificus. Interestingly, there is genetic diversity for the reaction norm between strains of Pristiochus pacificus and between different species of the genus Pristionchus. We are currently investigating the genetic (proximate) and evolutionary (ultimate) causes of the mouth dimorphism. The analysis of Recombinant inbred lines (RILs) indicates that a small number of loci are responsible for the differences in the developmental switch mechanism between the P. pacificus strains used in the generation of the RILs. Furthermore, we have also generated mutant lines where the reaction norm changes towards an increase in the ratio of stenostomatous worms. Mapping is ongoing in both the RILs and the mutant lines.
