Karim Ghali

For the last decades, evolution and maintenance of sex have been some of the major unsolved questions in evolutionary biology. Indeed, most eukaryotes are sexual, and fully asexual organisms are rare, despite many theoretical advantages of asexual reproduction.  The fact that sex is associated with considerable costs but maintained in the vast majority of organisms (the paradox of sex) can be explained by many different theories, focusing on direct short terms benefits of sex (e.g. Red queen dynamics, migration and spatial changes in selection, Hill-Robertson effect) or indirect long term advantages of sexual reproduction (e.g. Muller’s ratchet). Despite an increasing number of organisms used to address those questions, there is still a lack of example in natural populations.

During my Phd, I will use new model species to test different factors permitting to explain why some lineages remain sexual, as other displays a transition toward asexual reproduction.  Indeed, the genus of grass thrips Aptinothrips comprises four species, out of which two are obligate asexual (A. Karnyi, A.stylifer), one is sexual (A. elegans), and one where asexual and sexual lineages co-occurs in south Europe (A. rufus), and in which multiple transitions to asexuality have been observed.  This system is thus perfect to test the maintenance of sex, as it comprises multiple transitions to asexuality at the genus or species level, allowing us to make replicated comparisons between the two different reproductive modes.