Beewolf Pheromone

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Evolution of the sex pheromone of male European beewolves (Philanthus triangulum, Hymenoptera, Crabronidae)

Male European beewolves establish small territories in the vicinity of the females' nests and defend these territories against intruding males. They mark the vegetation with a cephalic gland secretion. Territories of several different males are often found close together, thereby costituting a lek situation in which females have an ideal opportunity to choose among potential mates. Females usually approach territories from the downwind side. Copulations with males often take place within the males' territories, and they are not preceeded by any kind of visual courtship behaviour. The sex pheromone consists of a number of compounds with Z-11-eicosenol making up the major component. Surprisingly, honeybees – the prey of the beewolf females – possess the same compound in their alarm pheromone. According to the sensory exploitation hypothesis we hypothesised a three step scenario for the evolution of the composition of the sex pheromone. First, honeybees smell of eicosenol. Second, female beewolves use eicosenol either to locate or identify their prey and have therefore evolved a high sensory sensitivity for this substance. Third, males have integrated this compound in their pheromone to attract the attention of receptive females. With a combination of behavioural assays and chemical analyses, we found evidence for all these steps. We are currently investigating whether females choose mates on the basis of this pheromone. We are particularly interested in whether the composition and/or amount of the male pheromone vary with size, age, relatedness, and geographical origin. Femals could then use such information on many different aspects of mate quality to choose the best mate. Using microsatellites, we are currently testing whether females choose adaptively among potential mates.

Fotos ? Martin Kaltenpoth

Publications

Kaltenpoth M, Kroiss J, Strohm E (2007) The odor of origin: kinship and geographical distance are reflected in the marking pheromone of male beewolves (Philanthus triangulum F., Hymenoptera, Crabronidae). BMC Ecology 7:11.

Schmitt T, Herzner G, Weckerle B, Schreier P, Strohm E (2007). Volatiles of foraging honeybees