Using high-speed video to observe mating, the researchers noted that each structure hooks, enlarged segments and spikes on the antennae appeared precisely designed to grasp females. They then looked at which genes were being expressed during development of the male antennae (just prior to maturation). Knowing the gene provides the opportunity to modify its expression, and therefore modify the male antennae. One gene looked promising so the researchers knocked down its expression during development using RNA interference.
"In this way, we were able to create males with a range of antennae from a simple female-like antennae all the way to the highly elaborate antennae with hooks and other grasping mechanisms of the males we see today," says Abouheif.
The researchers then tested a set of these males with differing antennae to determine their utility in grasping females. They found that as the antennae became more elaborate, mating success increased. "This means that the struggle over mating could account for the ever increasing elaboration of these antennae," says Rowe.
The study is unusual in bringing the tools of genetic model systems to a natural system where much is already known about the selective forces involved in shaping the traits under study. It presents one of the rare case studies (another is Darwin's finches) where a direct linkage has been described between known forces of selection, evolutionary change morphology, and the underlying genetic basis.
|Contact: Kim Luke|