Beyond protist generalizations: different evolutionary trajectories in closely related microbial species

Résumé fourni par la source

Abstract The processes underlying microbial diversity are inherently complex, so it is highly challenging to establish universal explanations and theoretical models of speciation. Using a population genetic approach, our study reveals that even closely related protist taxa with similar distributions, inhabiting overlapping ecological niches and comparable abundances, employ distinct speciation strategies. We investigated the population structure of two related species, Synura petersenii and Synura glabra (Chrysophyceae, Stramenopiles), across Europe. Using single-digest restriction-site-associated sequencing, we analyzed genomes of both species from a total of 43 distinct water bodies. A population pattern was present in both algal species, demonstrating their recent divergence and ongoing speciation. Nevertheless, the underlying drivers of genetic differentiation varied substantially. Synura petersenii exhibited a population pattern primarily associated with environmental factors, with conductivity emerging as the strongest habitat predictor of genetic structuring. In contrast, S. glabra demonstrated strict geographical boundaries and formed populations primarily according to geographical distance. We propose that divergences in population patterns between the two studied species arise due to differing mechanisms of distribution. By employing a balanced sampling design with comparable geographic coverage for both species, our study enables a robust comparison of their divergence and provides new insights into the complexity of speciation.

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