The genetics of male genital evolution unraveled: the tartan gene underlies differences in the size of genitalia between species

Tuesday, 17 September 2019

Fruitfly News

Scientists at Oxford Brookes University have discovered a gene that contributes to differences in the size of male genitalia between different species of flies.

The size and shape of male genitalia is strikingly diverse amongst animals. Biologists have been searching for the genes responsible for the evolution of these structures for decades. In research published in the journal Proceedings of the National Academy of Sciences (PNAS), Oxford Brookes researchers report the identification of a gene that contributes to differences in the size of male genitalia, between different species of fruit flies.

Lead researcher, Dr Daniela Santos Nunes commented on the findings: “Identifying the genes underlying differences in morphology (the form and structure of organisms) between species, and in particular, differences in genital structures that are involved in mating and reproduction, is important for us to be able to understand how biodiversity is generated and maintained”.

The article in the journal describes the quantitative mapping and functional work that led to the identification of tartan, as one of the genes responsible for the differences in clasper size between the species of fruit flies used in the study.

Dr Nunes explains: “The claspers are secondary genital structures present in many species of flies. Drosophila mauritiana has much larger and hairier claspers than Drosophila simulans and at least in these species, these structures appear to be important for successful copulation. This is because they lead to the opening of the oviscapt (the copulatory structure in females), either through stimulation or mechanical force.” 

The researchers were able to show that flies with the Drosophila mauritiana version of tartan, had larger claspers than flies with the Drosophila simulans version of tartan. 

Professor Alistair McGregor, the other senior author of the article,described the next steps: “Now we need to understand how this gene evolved to lead to the changes we see in the morphology of the claspers, without disrupting the development of these important structures. This will give us important insights into how evolution has modified development.”

Dr Nunes added: “ We can also go back to the ultimate causes of male genital evolution. Now we can test if males that only differ in the size and bristle number of their claspers have different reproductive success. Are males with larger claspers more or less likely to mate? And do they have more or less progeny than males with smaller claspers?”.  Basically we can finally answer the age old question: does size really matter?”

Find out more about the fascinating work underway in the Oxford Brookes University Department of Biological and Medical Sciences