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. In particular, the molecular principles of plasticity-associated evolution, such as genetic accommodation and assimilation are only partially understood. Our lab has extensively investigated the mouth-form plasticity in Pristionchus, both anatomically and molecularly. While mouth-from plasticity - i.e., the existence of wide-mouthed and narrow-mouthed morphs - manifests in the morphology of Pristionchus, it more strongly moulds the behaviour of the organism into being bacteriovorous or carnivorous.
In order to understand the evolutionary importance of such plastic traits, we utilize the plasticity of Pristionchus in an experimental evolution framework. The biology of Pristionchus makes it ideal for experimental evolution, since, on average, it takes only 3-5 days for a fertilized egg to reach adulthood at 20°C, and the worms can also be cryopreserved. Moreover, the extensive and unabated sampling of Pristionchus species and strains over the years, make it possible to subject a plethora of genetically variant natural isolates in the lab collection to experimental evolution.
Furthermore, Pristionchus species exhibit two distinct reproductive modes; while most the species in this genus are gonochoristic, i.e. outcrossing between males and females is essential for perpetuation of the population, few of the species are hermaphroditic and self-fertilizing. This diversity of reproductive modes opens up new avenues of investigation within the experimental evolutionary framework. In addition, previously identified environmental conditions - e.g. liquid vs solid culture, various bacterial regimes, different temperature values - all have been shown to affect the mouth-form plasticity.
By evolving Pristionchus species in the lab, we are actively investigating the role of phenotypic plasticity in evolution.
Yoshida, K., Rödelsperger, C., Röseler, W., Riebesell, M., Sun, S., Kikuchi, T. & Sommer, R. J. (2023): Chromosome fusions repatterned recombination rate and facilitated reproductive isolation during nematode speciation. Nature Ecology & Evolution, in press.