Identification of semiochemicals in bumblebees and their social parasites

• Applicants: Professor Dr. Manfred Ayasse; Professor Dr. Wittko Francke (†)
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2007 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 51257686

• Final Report Year: 2009

Final Report Abstract

Concerning our aim to identify chemicals involved in host nest recognition of the cuckoo bumblebee species, we could demonstrate that host-specific and non host-specific parasite females of the subgenera Psithyrus definitely distinguish between potential hosts and non-hosts by using the hosts’ olfactory nest-marking signals. Many substances of these nest marking signals have been identified, and bioassays with fractions of polar and non-polar compounds have shown that nest-searching females of the generalist parasite B. bohemicus and the specialist B. vestalis use different patterns of chemical compounds to recognize the common host, B. terrestris. We furthermore could identify semiochemicals with a function in regulation of reproduction in the host, B. terrestris, and the specialised parasite, B. vestalis. The higher relative proportions of wax type esters and aldehydes in egg-laying females indicate that they may have a function as a fertility signal in B. terrestris queens and workers as well as in the parasite B. vestalis. Furthermore, we could demonstrate that the parasite female, B. vestalis, after entering a host nest, performs chemical mimicry and produces an odour bouquet that matches that of their respective host queen B. terrestris. Several bioassays with natural extracts from glands and synthetic mixtures of GC-EAD active compounds have shown an inhibitory effect on the oogenesis of B. terrestris workers. These bioassays as well as behavioural observations revealed that the sources of the dominance signal include the Dufour´s gland and the sternal gland, which has been newly discovered and which is only possessed by social parasitic bumblebees.

Publications

• 2008. Fertility signals in the bumblebee Bombus terrestris (Hymenoptera : Apidae). Naturwissenschaften 95: 515-522
  Sramkova A, Schulz C, Twele R, Francke W and Ayasse M
  
• 2009. Chemical ecology involved in invasion success of the cuckoo bumblebee Psithyrus vestalis and in survival of workers of its host Bombus terrestris. Chemoecology 19: 55-62
  Sramkova A & Ayasse M
  
• 2009. The role of trail pheromones in host nest recognition of the social parasitic bumblebees Psithyrus bohemicus and Psithyrus rupestris (Hymenoptera: Apidae). Chemoecology
  Bunk E, Sramkova A and Ayasse M