Co-option and adaptation of novel gene duplications for pheromone activity in a dusky salamander

CO-OPTION AND ADAPTATION OF NOVEL GENE DUPLICATIONS FOR PHEROMONE ACTIVITY IN A DUSKY SALAMANDER. Kari A. Leichty April 18,2012 For more than a hundred million years, male plethodontid salamanders have utilized non-volatile, proteinaceous courtship pheromones to regulate female mating receptivity and promote mating success. These pheromones which are delivered after courtship has commenced and do not act as chemical attractants are delivered from a male's submandibular (mental) gland to the female salamander either by an olfactory mode or transdermally. For approximately 20 years, research on plethodontid courtship pheromones has focused on those involved in olfaction, using the red-legged salamander (Plethodon shermani) as a model. However, the olfactory system is a relatively recent adaptation (~20 million years ago) employed only by a single clade of large eastern Plethodon species. In contrast, for the majority ofplethodontids (~350/380 species) the male scratches the back of the female with hypertrophied premaxillary teeth and rubs his gland over the abraded site to transdermally deliver pheromones. Desmognathus ocoee has served as the model for transdermal delivery, however less is known about this species. The purpose of this study was to evaluate the hypothesis that sexual selection has favored unique pheromone composition and structural motifs in different modes of