Sex pheromones and reproductive isolation in four european small ermine moths

Abstract

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 ofY. evonymellus,Y. cagnagellus,Y. padelius, andY. 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 theE isomer as primary sex pheromone components.Y. cagnagellus differs from the rest of the species by having only a small amount (1.5%) ofE isomer relative toZ isomer in its pheromone. The closely relatedY. padelius has a three-component pheromone including large amounts (ca. 400%) of (Z)-11-hexadecenyl acetate (Z11-16:OAc) in addition toZ11-14: OAc (100%) andE11-14: OAc (34%).Z11-16: OAc appears to reduce trap catches ofY. evonymellus andY. 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'sYponomeuta species.

Evolution of multicomponent pheromone signals in small ermine moths involves a single fatty-acyl reductase gene

“…In Yponomeuta spp. pheromone production is typically acquired 2 to 4 d after eclosion (21) and the diel rhythmicity in pheromone production and periods of calling behavior are synchronized to be maximal at dawn (28). Quantitative PCR was used to examine the changes in transcript level of the pheromone biosynthetic candidate Yev-pgFAR in adult Y. evonymellus females at different ages and over a 24-h period.…”

“…In six sympatric species, including Y. evonymellus and Y. padellus, the two primary components are Z11-14:OAc and E11-14:OAc, and complete reproductive isolation is ensured by the use of additional pheromone components ( Fig. 1) (21). Y. rorellus is peculiar in that it uses only saturated (14:OAc) but no unsaturated components as pheromone (22).…”

Small Ermine Moths (Yponomeuta): Their Host Relations And Evolution

“…The majority of Yponomeuta pheromones conform to the pattern observed in many other Lepidoptera in that pheromones have unsaturated components with double bonds in particular positions and a dominance of Z-geometry desaturation (5) (55) does not logically follow from the pheromone composition (93,94). evonymellus and Y. vigintipunctatus, although genetically far apart (Figure 1) (100), share the same pheromone system, which may indicate the primitive state in Yponomeuta (93,94).…”

“…Further refinement and extension to all nine West European representatives of Yponomeuta confirmed these earlier findings and suggested that Zll-14:OAc and EII-14:OAc are important components of the pheromones of most species (146). COMPOSITION Many of the actual pheromone components of Yponomeuta species have been predicted using electrophysiological screening (146), although the predictive value of this technique is hampered by our poor understanding of the perception of multicomponent pheromones (93,94). The pheromonal composition of all Yponomeuta species has been elucidated successively, and in subsequent tests, synthetic blends competed with those emitted by virgin females.…”

“…evonymellus and Y. vigintipunctatus, although genetically far apart (Figure 1) (100), share the same pheromone system, which may indicate the primitive state in Yponomeuta (93,94). In nature, interspecific matings between evonymellus and Y. vigintipunctatus are simply impossible because of asynchronous occurrence, as well as several other differences in life history characteristics (68).…”