Sex pheromones and reproductive isolation in four european small ermine moths

Reproductive isolation among four sympatric small ermine moths (Yponomeuta) is analyzed in terms of niches in the sexual communication channel. Potential pheromone components were identified from pheromone gland secretions of Y. evonymellus, Y. cagnagellus, Y. padelius, and Y. vigintipunctatus by gas chromatography with flame ionization and electroantennographic detection and tested for behavioral activity in the field. The species were found to share (Z)-11-tetradecenyl acetate (Z11-14: OAc) in combination with varying proportions of the E isomer as primary sex pheromone components. Y. cagnagellus differs from the rest of the species by having only a small amount (1.5%) of E isomer relative to Z isomer in its pheromone. The closely related Y. padelius has a three-component pheromone including large amounts (ca. 400%) of (Z)-11-hexadecenyl acetate (Z11-16:OAc) in addition to Z11-14: OAc (100%) and E11-14: OAc (34%). Z11-16: OAc appears to reduce trap catches of Y. evonymellus and Y. vigintipunctatus when added to the pheromone. Although these species are the two most distantly related European small ermine moths, they seem to share the same sex pheromone, i.e., Z11-14:OAc (+20%E) and (Z)-11-tetradecenol. Our interpretation is that this might have been the sex pheromone of the ancestor of today's Yponomeuta species