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Integrative evolutionary biology

Ralf Sommer

Ralf Sommer

  • Diplom in Biology 1989, RWTH Aachen & University of Tübingen
  • PhD work 1989-92 at the Ludwig-Maximilians University, Munich
  • Research fellow 1993-95 at California Institute of Technology, Pasadena, CA, USA
  • Director at the MPI since 1999

Research Interest

Multicellular life is characterized by astonishing phenotypic diversity, but our understanding of how this diversity is generated as a result of historical processes is still limited. We use a highly interdisciplinary approach that integrates development, ecology and population genetics to unravel the mechanistic changes that give rise to evolutionary alterations and novelty. For this to be achieved, we established the free-living nematode Pristionchus pacificus as a model system in evolutionary biology. Specifically, in P. pacificus we can combine laboratory studies building on forward and reverse genetic, genomic and transgenic tools with field work in ecology and population genetics.
One of our core research areas is developmental (phenotypic) plasticity and associated genetic and epigenetic mechanisms. Developmental plasticity, the ability of a genotype to produce distinct phenotypes in response to environmental variation, represents a major facilitator of phenotypic diversification. We focus on a mouth-form dimorphism of Pristionchus associated with the development of teeth-like denticles. During development, young larvae irreversibly decide to become either eurystomatous (Eu) or stenostomatous (St). Eu and St animals differ in the shape of the buccal cavity and the quality and quantity of their teeth (Bento et al., 2010). St animals are strict bacterial feeders, whereas Eu animals are also predators of other nematodes.   Using genetic approaches, we have been able to elucidate the molecular mechanisms of plasticity for the first time. We identified, the molecular nature of developmental switch genes that regulate mouth-form plasticity (Ragsdale et al., 2013; Kieninger et al., 2016). More recently, we identified that one of the developmental switch genes, eud-1, is regulated by various epigenetic mechanisms (Serobyan et al., 2016).
Our ongoing research, investigates the genetic and epigenetic control of mouth-form plasticity and how various environmental factors (culture condition, temperature, diet) interact with the core genetic machinery and we just begun to look into potential trans-generational effects based on the previous experience of animals.

Selected Reading

1) Bumbarger DJ, Riebesell M, Rödelsperger C, Sommer, RJ (2013): System-wide rewiring underlies behavioral differences in predatory and bacterial-feeding nematodes. Cell, 152, 109-119.

2) Wang X,  Sommer, RJ (2011): Antagonism of LIN-17/Frizzled and LIN-18/Ryk in nematode vulva induction reveals evolutionary alterations in core developmental pathways. PLoS Biology, 9, e1001110.

3) Bento G, Ogawa A, Sommer, RJ (2010): Co-option of the hormone-signalling module dafachronic acid–DAF-12 in nematode evolution. Nature, 466, 494-497.



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Scanning electron micrograph of Pristionchus pacificus. 

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Predatory feeding of P. pacificus on another nematode.