Ahmed Hasan's new paper on using next-generation sequencing data from *Chlamydomonas reinhardtii* to examine variation in recombination rate across the genome
Recombination rate variation and infrequent sex influence genetic diversity in Chlamydomonas reinhardtii
Genome Biology and Evolution, evaa057, https://doi.org/10.1093/gbe/evaa057
When harmful and beneficial mutations are found on the same genetic background, selection is less efficient at removing the former, which can lead to reductions in genetic diversity. However, by shuffling genetic material every generation, recombination can unlink harmful and beneficial mutations, thereby facilitating selection. The picture is more complicated in species that are only periodically sexual, such as many microbial eukaryotes; since these species can reproduce sexually (i.e. with recombination) or asexually, the effective rate of recombination depends on the frequency of sex. This means that in species with high recombination rates, infrequent sex may lead to effects of selection at linked sites all the same.
In this paper, we used next-generation sequencing data from natural populations of the periodically sexual microbe *Chlamydomonas reinhardtii* to examine variation in recombination rate across the genome and estimate the rate of sexual reproduction in nature. We observed variation in recombination rate across the genome by annotation, finding that recombination rate is highest immediately flanking genes. We also found a positive relationship between genetic diversity and recombination rate across the genome, indicative of selection at linked sites. Finally, we estimated the rate of sex that occurs in natural populations, estimating a sexual cycle every ~840 generations. We argue that the relatively infrequent rate of sex and large effective population size increases the influence of selection at linked sites on genetic diversity in the *C. reinhardtii* genome.