Sharing of Pyrazine Semiochemicals between Genera of Sexually Deceptive Orchids

Abstract

It has recently been discovered that novel di-, tri- and tetra- substituted pyrazines are semiochemicals in Drakaea, an orchid genus that secures pollination by the sexual deception of male thynnine wasps. We examined if similar pyrazines were also present in the distantly related Caladenia barbarossa, a sexually deceptive orchid that is also pollinated by a thynnine wasp. Here we report for the first time the occurrence of two pyrazines, (3,5,6-trimethylpyrazin-2-yl)methyl 3-methylbutanoate (1) and 3-(3-methylbutyl)-2,5-dimethylpyrazine (2) in the orchid genus Caladenia. The former is known as a semiochemical involved in pollinator attraction in Drakaea livida. This convergence of floral odour between distantly related plants provides an exciting opportunity to understand the evolution and molecular basis of this sophisticated chemical mimicry.