The role of sex differentiation in social insect caste differentiation
Evolution, Anthropology
Final Report Abstract
In contrast to common belief, ant caste is determined in the embryo and not the larva. In worker-destined embryos of the ant Cardiocondyla obscurior, the default female developmental trajectory is interrupted even before the gonadal precursor cells acquire a sexual identity in queens. miRNA and mRNA expression in embryos reveal three distinct phenotypic entities: males, females, and "neuters", as Darwin coined the sterile worker caste in "On the Origin of Species". Based on these results we propose that haplodiploidy, in conjunction with insect sex determination, allows for the expression of a third dimension on the sex continuum, thus facilitating the evolution of individuals which develop traits their parents do not have. To conclude: Ants align along a range of so-called developmental constraints, the degree to which species exhibit worker sterility. Cardiocondyla is one of only 11 genera (out of ~300) with completely sterile workers, i.e. workers without any traces of reproductive organs. C. obscurior is thus a model to study processes at one extreme end of social complexity. With regard to caste polyphenism it is one of the best studied species.
Publications
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Darwin’s “neuters” and the evolution of the sex continuum in a superorganism. Cold Spring Harbor Laboratory.
Oettler, J.; Wallner, T.; Dofka, B.; Heinze, J.; Eichner, N.; Meister, G.; Errbii, M.; Rehli, M.; Gebhard, C. & Schultner, E.
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Queens control caste allocation in the ant Cardiocondyla obscurior. Proceedings of the Royal Society B: Biological Sciences, 290(1992).
Schultner, Eva; Wallner, Tobias; Dofka, Benjamin; Brülhart, Jeanne; Heinze, Jürgen; Freitak, Dalial; Pokorny, Tamara & Oettler, Jan
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Sex- and caste-specific developmental responses to juvenile hormone in an ant with maternal caste determination. Cold Spring Harbor Laboratory.
Brülhart, J.; Süß, A.; Oettler, J.; Heinze, J. & Schultner, E.
