Researcher Jun Abe the Institute of Center for Liberal Arts has solved the puzzle of wasps that rarely produce males

Along with Ryosuke Iritani (Researcher, RIKEN Interdisciplinary Theoretical and Mathematical Science Program), Koji Tsuchida (Professor, Faculty of Applied Biological Sciences, Gifu University), Yoshitaka Kamimura (Associate Professor, Faculty of Business and Commerce, Keio University), and Stuart West (Professor, Department of Zoology, Oxford University), Jun Abe (Researcher, Institute of Center for Liberal Arts, Meiji Gakuin University) has unraveled the mystery of wasps that produce very low ratios of males.

Key points:

• • It was previously unknown why Melittobia wasps produce extremely female-biased offspring sex ratio (about 2% sons), but it has now been revealed as a kind of cooperative behavior by which mothers laying eggs together can efficiently leave behind each other’s descendants.
• • In Melittobia, offspring sex ratios are adjusted according to kinship between mothers, with extremely few males being laid when related mothers lay eggs together.
• • DNA analyses and theoretical calculations show that Melittobia can increase the number of each other’s descendants by producing more females and fewer males, thereby avoiding unnecessary competition for mates among related sons.
• • It was indicated that mothers are unable to directly recognize mutual kinship, and so indirectly estimate kinship from their own experience, based on whether they dispersed nearby (making it likely to encounter relatives) or far away (making it unlikely to encounter relatives).

This is a world-first confirmation of sex ratio regulation according to numbers of and kinship between mothers in any organisms. The authors also showed that such regulation is determined by differences in dispersal methods of mothers, rather than their direct recognition of kinship with other individuals. This discovery is expected to be applied not only to understanding of wasp behavior and sex ratio regulation, but also to understanding of social behavior in general, particularly when organisms behave selfishly and when they behave cooperatively.

The results of this research were posted online in the Proceedings of the National Academy of Sciences of the United States (PNAS) on 10 May 2021, 15:00 EST (11 May 2021, 04:00 JST):
https://www.pnas.org/content/118/20/e2024656118