Pollinators as isolation mechanisms: field observations and field experiments regarding specificity of pollinator attraction in the genus Ophrys (Orchidaceae und Insecta, Hymenoptera, Apoidea)

摘要

It is demonstrated that the biological species concept of the genus Ophrys corresponds to the general concepts of Ernst Mayr. On the example of two closely related forms of the fusca group in Andalucia, it is shown how to handle the different criteria of the biospecies concept. One is the high specifity of attraction of a male bee followed by a complex pseudocopulation behaviour which enables the correct pollen transfer within the species. The high specifity is caused by a highly remarkable imitation of the sexual pheromones of the mimicked female of the pollinator. Sexual pheromones of animals act as intraspecific signals which result in attractions of only males of the same species. Exactly this specific behaviour is triggered by the Ophrys flower, too. Thus the pollinator male is attracted only to those flowers which have the correct mixture of the pheromone molecules. To further ensure success the pollinating males also select other characters of the Ophrys flower as labellum size, colour, labellum hair characters, phenology and possibly habitat selections etc. In the sexual reproduction behaviour of the male insect acts as pregamic isolation mechanisms for the given Ophrys like for their own female.