Male fertility and social polymorphism in ants

ULB main applicant

Prof. Serge Aron, Faculty of Science

UNIL main applicant

Prof. Michel Chapuisat, Faculty of Biology and Medicine




  • Joint research project


Animal societies vary greatly in their organization, from simple family groups to more complex societies. The causes underlying this variation are still largely unknown. The Alpine silver ant Formica selysi is an ideal system to study variation in social organization, because single-queen and multiple-queen colonies co-exist within populations. Furthermore, individuals from these two social forms differ in multiple morphological, behavioural and life-history traits.

Recently, it has been shown that the social organization of colonies in the Alpine silver ant is controlled by a supergene, i.e. a large group of linked gene. There is ongoing gene flow between both social morphs, as there is no sign of genetic differentiation between them in the rest of the genome. The mechanisms allowing for the maintenance of this genetically-based social polymorphism remain enigmatic.

This collaborative research project aims at studying whether male fertility differs between the monogynous and polygynous social forms, with the hypothesis that males originating from monogynous colonies produce more sperm than males originating from polygynous colonies, and that this difference in male reproductive potential plays a role in the maintenance of the genetic polymorphism in nature.

In order to test this hypothesis, a rapid, efficient and reliable method will be used for assessing sperm number and viability from males emerging from each social form: flow cytometry. Furthermore, how male fitness affects the maintenance of the social polymorphism will be studied, using behavioural experiments and genetic analyses. Ultimately, this research will reveal if differences in male fertility are associated with social organization, and if they contribute to maintaining polymorphisms in animal populations.

This proposal strongly capitalizes on the common research interests of both groups, and on the complementarity of the methods developped in Lausanne and Brussels respectively.


  • Summer 2017: Collection of males in the field
  • Autumn 2017: Research internship at ULB
  • Autumn 2017 to autumn 2018: Processing of samples in Brussels and Lausanne
  • Academic year 2018-2019: Meetings in Lausanne and Brussels for data processing and analysis.
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