Evolution of parthenogenesis in the ant Cataglyphis cursor
C. cursor is a very peculiar ant as the workers are able to produce both males and females by thelytokous parthenogenesis. This species is monogynous and we found that the queen is also able to reproduce by parthenogenesis but use it only for producing the new queens. The queen mates with several males and use sexual reproduction for producing workers. By using selectively asexual reproduction for the caste that is transmitting its genes and sexual reproduction for workers, the queen exploits the advantageous aspects of both modes of reproduction (Pearcy et al. 2004). She avoids the two-fold cost of sex in term of gene dilution during gene transmission (production of new queens) while maintaining the benefits of a genetically diverse workforce. However, we recently found some variation in the rate of parthenogenesis among population and colonies (Doums et al. 2013 JEB). One of the factors that could affect maintenance of sex is inbreeding depression and the genetic load associated to diploid male production linked to inbreeding (Doums et al. 2013 BES). We plan to investigate the importance of inbreeding depression and the variation in the rate of thelytoky among the range of species distribution.
In social hymenoptera (ants, wasp and bees), sexual selection is not considered as a strong selective force compared to kin selection that play a major role for understanding the evolution of social life. However, mating strategies can be of considerable importance when the queen mate with several males as male competition can also take place within the spermatheca between sperms but also between workers of different fathers within the colony. The PhD project that is currently undertaken by Florence Helft aim at investigating the potential for sexual selection in an peculiar ant species known for having both males and females mating many times close to the nest entrance. We showed that by aggressing males, workers affect the probability success of males in gaining access to the gynes. We are currently investigating the importance of this process under natural conditions.
Collaborators : T. Monnin
At a first glance, social life could favor the infection and transmission of pathogens thanks to the physical and genetic proximity of individuals within the colonies. Social insects have evolved various defences mechanisms based on social behaviors (dependent of others individuals in the colony) and individual immunity. During her PhD, Claudia Westhus (in co-supervision with Sylvia Cremer) investigates the importance of individual experience of workers in their hygienic behavior efficiency, in particular to remove entomopathogenic fungal on larva and dead individuals. We are also testing whether individual immune system is linked to division of labour.
Collaborators : S. Cremer
Studying the mechanisms that allow for the production, survival and selection of novel phenotypes is crucial to understand biodiversity and evolution. Phenotypic plasticity has recently been considered as a factor favouring the production of novel phenotypes after environmental changes. In polyphenic organisms, i.e. exhibiting phenotypic plasticity with discrete alternative forms (e.g. butterfly seasonal morphs), novel phenotypes can be generated by combining traits expressed in alternative phenotypes. The occurrence of such new phenotypes is often observed at very low frequency and their production can be increased after environmental changes. We are currently investigating whether environmental changes (temperature) and hormonal treatments affect the rate of production of intermediate morph between queens and workers (intercastes) and the morphology of workers and sexuals in order to assess the level of phenotypic plasticity in different populations in the ant Temnothorax nylanderi. We are also investigating the level of intercaste production and morphological variation among natural populations as well as the amount of genetic differentiation among populations.
Collaborators : M. Molet