Effects of functionally asexual reproduction on quantitative genetic variation in the evening primroses

Sex is the spice of life! This is the conclusion that former M.Sc. student Ryan Godfrey (Johnson Lab) came to in his paper “Effects of functionally asexual reproduction on quantitative genetic variation in the evening primroses”, published in American Journal of Botany. Why organisms have sex at all is a conundrum that has puzzled biologist for over a century. An early hypothesis was that sex maintains genetic variation within populations, increasing the probability of survival for individuals born to sexual mothers compared to asexual mothers. Surprisingly, this hypothesis has been tested only in a small number of animal systems and with variable results, and it has never been examined in plants. Ryan conducted a large-scale experiment in which he compared genetic variation for multiple plant traits within four independently evolved asexual evening primrose species and their closely related sexual relatives. Ryan found that consistent with the hypothesis, sexual populations tend to maintain greater genetic variation within populations for multiple plant traits. He also found evidence to suggest that asexual populations exhibit greater differentiation between populations, which might help to explain why asexual evening primrose lineages exhibit greater speciation rates than asexual lineages. Overall, these results provide some of the first evidence that sexual reproduction maintains genetic variation within populations and limits differentiation between populations.