Figures
Evolving past the ‘the point of no return’.
The left panel shows a colony of ants (of the species Camponotus floridanus) with a queen (the large individual in the center) surrounded by her female worker ants. Understanding how worker ants evolved to have a reduced reproductive capacity is a major challenge in biology. The right panel shows the position of a protein called Vasa (green) in oocytes from a normal queen (top) and a worker (bottom): vasa is a highly conserved developmental gene that specifies the germ cells in all animals and is necessary for fertility. In the normal queen oocyte the Vasa protein is correctly positioned at the posterior pole of the oocyte (white arrowhead). However, in many worker oocytes the Vasa protein (white star) is not in the correct position, and this leads to developmental problems, including a reduced capacity to produce viable male offspring (Khila and Abouheif, 2008). The presence of this ‘reproductive constraint’ in worker ants but not in queens allows the worker ants to use their ovaries to produce eggs that can be used to feed the colony. (Image credits: Guy L’Heureux [left]; Abderrahman Khila [right])
