Poster Presentation Society for Molecular Biology and Evolution Conference 2016

The Mechanistic, Genetic, and Evolutionary Basis of Worker Sterility in the Social Hymenoptera (#587)

Isobel Ronai 1 , Vanina Vergoz 1 , Benjamin P Oldroyd 1
  1. The University of Sydney, Sydney, NSW, Australia

Extreme reproductive skew towards particular females is a defining feature of the social insects and workers are completely sterile in at least thirteen genera. The evolution of worker sterility is problematic because an individual that has decreased fertility has reduced direct fitness. In order to understand how worker sterility evolved it is essential to identify the mechanistic basis of worker sterility. We show that the developmental mechanisms that underlie worker sterility are ‘reproductive control points’ that reduce reproductive capacity in workers. We propose that environmental cues (nutritional and social) interact with particular signalling pathways in the worker and regulate worker fertility through reproductive control points both pre- and post-eclosion. We have identified eight gene signalling pathways that are likely to be involved in regulating worker fertility in honey bees: IIS; juvenile hormone; ecdysteroid; mTOR; dopamine; MAPK; Egfr and Wnt. We suggest that the common mechanism underlying all the reproductive control points is programmed cell death, an active process that causes the worker’s reproductive organs to degenerate. An example of a reproductive control point is the abortion of oocytes during mid-oogenesis in the honey bee. The presence of the queen affects the expression of Anarchy in the ovaries of honey bee workers and during mid-oogenesis Anarchy transcripts localise to these degenerating oocytes. These reproductive control points are likely to have been involved in the ancestral emergence of worker sterility from a solitary insect.