Press release: No sex, no problem!
Nr. 200/2017 - 12.10.2017
Biologists from Goettingen analyse how loss of sex affects the genetic makeup of oribatid mites
(pug) Sexual reproduction is linked to various benefits for the survival of a species. Amongst others, sex counters the accumulation of accidentally occurring deleterious mutations by allowing for exchange of genetic material. According to the scientific consensus, loss of sex in favour of clonal reproduction leads to a stepwise accumulation of deleterious mutations, which eventually causes extinction of a species. Now scientists of the Universities of Göttingen and Lausanne found out, that ancient asexual oribatid mites are more effective in purging deleterious mutations as compared to their sexual relatives. The results are reported in the current issue of Nature Communications.
“Up to now, experimental evidence is scarce and restricted to species that lost sex in recent times”, says Alexander Brandt, first author of the study, who works in the animal ecology group at the Johann-Friedrich-Blumenbach Institute of Zoology and Anthropology of Göttingen University. To unravel the consequences of loss of sex in the long term, the scientists have sequenced and analysed the genetic makeup of various sexual and ancient asexual oribatid mites. The findings are surprising: ancient asexual oribatid mites are more effective in purging deleterious mutations as compared to their sexual relatives.
“Oribatid mites are well suited for analysing the long-term consequences of asexual reproduction, as within this animal group, sex was lost millions of years ago several times independently”, explains Dr. Jens Bast, research fellow at the University of Lausanne and senior author of the study. “The discovery of asexual oribatid mites purging deleterious mutations more effectively as compared to their sexual relatives indicates the existence of a certain peculiarity in oribatid mites which enables them to survive without sex in evolu-tionary time scales”, adds Brandt.
So far, scientists can only speculate about the nature of the peculiarity: the population sizes of oribatid mites may play a role. The number of animals that make a population has, just like mixing up the genomic makeup, a strong influence on how effective natural selection counters the accumulation of deleterious mutations. The fact that populations of asexual oribatid mites are on average substantially larger as compared to sexual species indicates that the observed effective natural selection might indeed be due to their espe-cially large populations. This allowed at least some species of oribatid mites to survive without sex for millions of years.
Original Publication: Brandt et al., Effective purifying selection in ancient asexual oribatid mites, Nature Communications 2017
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