Integrative Evolutionary Biology - Ralf J. Sommer

Integrative Evolutionary Biology - Ralf J. Sommer

We take an integrative approach and try to link evo-devo with population genetics and evolutionary ecology by studying the nematode Pristionchus pacifius, which lives in a defined scarab beetle ecosystem.

How do developmental processes change during evolution? We take an integrative approach and try to link evo-devo with population genetics and evolutionary ecology by studying the nematode Pristionchus pacifius, which lives in a defined scarab beetle ecosystem.

We link development, ecology, and population genetics in a highly integrative approach to study how novel and complex traits evolve as a result of historical processes. We focus on developmental (phenotypic) plasticity as a facilitator for the evolution of novelty, complex traits, and phenotypic divergence. Despite the modern synthesis neglect of developmental plasticity and lack of sufficient insight into the evolution of novel structures, a theoretical framework has been built in the last two decades that highlights plasticity as a key concept in evolutionary biology (West-Eberhard 2003, Sommer 2020).

The Role of Plasticity in Evolution

However, a complete appreciation of plasticity and its role in evolution requires the identification of associated molecular mechanisms; in the last decade, my laboratory has arguably provided the most detailed molecular understanding of any plastic trait. First, we identified developmental switches that can sense the environment and reprogram development, thereby confirming long-standing theoretical predictions. Second, we have determined the downstream gene regulatory network (GRN) that guides phenotypic execution of alternative phenotypes. These findings, for the first time, demonstrate that plasticity is indeed consistent with the modern synthesis. More importantly, they provide a molecular framework to elucidate the mechanisms of plasticity-associated evolution from the i) origin of plasticity, through ii) genetic accommodation, to iii) final assimilation (canalization). These three steps will be the foundation of our research in the coming decade. 

The Model System Pristionchus pacificus

Using the free-living nematode Pristionchus pacificus as a model system, we combine laboratory studies of plasticity (forward and reverse genetics, genomics, transgenesis, experimental evolution) with field work (ecology and natural variation). In addition, we couple our model system approach with macro-evolutionary comparisons, utilizing more than 1,500 strains of P. pacificus and around 50 culturable Pristionchus species that have been collected globally ( Our established field station on La Réunion, an island in the Indian Ocean that harbors the complete worldwide genetic diversity of P. pacificus, serves as a microcosm to investigate developmental plasticity and its role in the environment and the nematode ecosystem.

Departmental Research Areas

Developmental Plasticity: A Facilitator of Novelty
Environmental responsiveness and phenotypic plasticity are found everywhere in nature. All organisms are exposed to an environment and most of these environments are changing constantly, often in an unpredictable manner. Not surprisingly therefore, plasticity is found in all domains of life and at all levels of biological organization. more
Experimental Evolution in Pristionchus
The emergence of phenotypic diversity from an identical stock of genetic information – i.e., polyphenism – remains one of the most fascinating phenomena in the living world. Despite a wealth of literature on the essence of plasticity and its prevalence in nature, the role it plays in adaptive evolution is yet to be fully elucidated. more
Pristionchus – Population Genetics and Ecology
One of the central aims of the Department is to work towards a better integration of studies on macroevolution, microevolution and ecology with developmental genetics and evo-devo. more
Microbial Interactions – Pathogenicity
Nematodes and bacteria are major components of the soil ecosystem. Many nematodes use bacteria for food, whereas others evolved specialized bacterial interactions ranging from mutualism to parasitism. Little is known about the biological mechanisms by which nematode-bacterial interactions are achieved. more
Pristionchus – Biology, Taxonomy and Phylogeny
Our work since 2004 revealed that nematodes of the genus Pristionchus live in close association with certain beetles. We carried out numerous field trips to locations in Western Europe, the Eastern United States, South-Africa and Japan. From 25,000 beetles, we established more than 8,000 Pristionchus isolates, which fall into 39 species, most of which are cryptic.  more
Pristionchus – Molecular Toolkit
Pristionchus pacificus is an attractive model organism for laboratory studies based on several technical features. A number of tools have been established over the years that allow mechanistic studies in this nematode. more
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