Then they inserted tiny electrodes into cells of the moths' antennae and measured how neurons in the antennae responded to the pheromones of the two species. They found that in each male the antennae neurons' response was largely controlled by which of the species' receptor genes it had inherited.
"In the end, the finding that big changes in the moths' responses to pheromones are controlled by such a small genetic change is a first step toward understanding how the thousands of moth species evolved," Gould says.
The puzzle, or evolutionary paradox, has been that within each moth species "natural selection constantly acts against any female that makes a novel pheromone blend that isn't recognized by males of its species," Gould says. "And males that have a mutated receptor gene that recognizes an as-yet-unevolved pheromone will have a hard time finding a mate."
This has led some to assume that a new moth species could evolve only if genetic changes occurred in the male and female at the same instant in evolutionary time which is highly unlikely.
"In the narrow sense, the research is about the evolution of sexual communication and speciation," Gould says. "But in a broader sense, it is about the evolution of what are sometimes called characteristics with irreducible complexity. Irreducible complexity is the idea that some traits are so complicated that there's no way for them to have evolved by natural selection.
"Moths seem to possess an irreducibly complex mating system," he says, "but perhaps the puzzle of how this system evolved has simply been difficult to solve."
Gould and his colleagues hope that, armed with a new understanding of the male sexual communication genes plus knowledge of the female genes from previous studies, they may now be in a position to recreate the evolutionary events involved in moth specia
|Contact: Dee Shore|
North Carolina State University