Genetic Variability of the Mating Recognition Gene in Populations of Brachionus plicatilis

Abstract

The development of reproductive barriers promotes within-species divergence and is a requisite for speciation to occur. Mate recognition in the rotifer B. plicatilis is mediated through a surface glycoprotein called Mating Recognition Protein (MRP). Here we investigate the genetic variation of the mmr-b, MRP coding, gene in different natural populations of B. plicatilis from the Iberian Peninsula, that present different degree of population differentiation, with known adaptive divergence in some cases. The MRP gene consists of several nearly identical tandem repeats. We found a relatively high diversity within and among populations both in the number of repeats, as well as in the nucleotide sequence. Despite that most changes are neutral, variation that can potentially affect the protein function was found in two polymorphic sites within a repeat in some of these populations. Although being mostly subject to stabilizing selection, we have found a noticeable pattern of increasing mmr-b gene diversification correlated to increasing differences in environmental factors. The interplay between genetic differentiation, local adaptation and differentiation of the mating recognition system can lead to speciation events in nearly sympatric populations.

Insight into incipient reproductive isolation in diverging populations of Brachionus plicatilis rotifer

“…With both predictors being collinear, the correlation with geographic distance in LA is likely spurious to some extent. As another piece of evidence, genetic differentiation in the mmr-b gene, which codes for the receptor responsible for mating recognition, increases with ecological distance (Jezkova et al, 2022).…”

“…They show local adaptation affecting their sexual reproduction patterns, adjusting them to variation in environmental predictability (i.e., high propensity to sex in populations with low environmental predictability Franch-Gras et al, 2017a, b). A recent study on the diversity of the gene mmr-b, which is involved in mate recognition, has shown that despite being under stabilizing selection, a correlation is found between gene diversification and differences in environmental factors when comparing B. plicatilis populations (Jezkova et al, 2022). Brachionus plicatilis belongs to a species complex, and the divergence of mmr-b among the species of the complex has also been documented (Gribble & Welch, 2012).…”