Evidence for directional selection acting on pheromone-binding proteins inthe genus Choristoneura

Patterns of nucleotide variation consistent with the action of natural sele ction have been discovered at a number of different gene loci. Here, pherom one-binding proteins (PBPs) are examined to determine if selection has acte d to fix amino acid changes in PBPs in lineages in which pheromone changes have occurred. PBPs from five different species of moths in the genus Chori stoneura were sequenced, along with the PBP of Argyrotaenia velutinana, whi ch serves as an outgroup. Three independent major pheromone changes are rep resented within this group of five Choristoneura species. Two different lin eages show evidence for selection based on polymorphism and divergence comp arisons and comparisons of rates of replacement evolution to silent and non coding evolution. Along one of these lineages, leading to Choristoneura fum iferana, there has been a change to an aldehyde pheromone from an acetate p heromone. The second branch does not appear to be associated with a major p heromone change. Other branches in the tree show a trend toward greater rep lacement fixation than expected under neutrality. This trend could reflect undetected selective events within this group of PBPs. Selection appears to have acted to fix amino acid changes in the PBP of moths from the genus Ch oristoneura, but it is not clear that this selection is due to pheromone ch anges between species.