How asexual reproduction affects the evolution of genomes

In the course of evolution, animals have repeatedly shifted from sexual to asexual reproduction. The first evidence of the consequences of parthenogenesis – a type of asexual reproduction – on genome evolution is reported in an international study co-led by scientists at the University of Lausanne and the SIB Swiss Institute of Bioinformatics. The findings help to explain why species reproducing in this way are generally more vulnerable in the wild, where environments change continuously. The study is published today in Science Advances.

The consequences of asexual reproduction

The study, led by Kamil Jaron and Darren Parker and co-supervised by Tanja Schwander and Marc Robinson-Rechavi from the Department of Ecology and Evolution (DEE) at UNIL and Nicolas Galtier at the Institute of Evolutionary Science of Montpellier (France), has demonstrated for the first time the consequences of parthenogenesis on the evolution of the genomes of certain animals. Three major effects have been reported: loss of efficiency in selecting mutations conferring greater reproductive success, reduction in genetic diversity and drastic reduction in heterozygosity.

Stick insects as study species

The results were achieved using stick insects, specifically the genus Timema, as study species. The scientists discovered that sexual reproduction favours rapid adaptation and genetic diversity in natural populations of stick insects. They were thus able to empirically validate predictions initially made using theoretical approaches, such as why species reproducing asexually were generally more vulnerable in the wild, where environments change continuously. The experts analyzed the genomes of five asexual Timema species and of closely related sexual species, and compared their transposable element contents (DNA sequences that can change their position within a genome), genes evolving under positive selection and heterozygosity. Analysis included the use of OrthoDB, part of the SIB Resource SwissOrthology, to identify corresponding genes across all species considered, in order to compare their evolution.