title: Pyrazines Attract Catocheilus Thynnine Wasps.
abstract: Five previously identified semiochemicals from the sexually deceptive Western Australian hammer orchid Drakaea livida, all showing electrophysiological activity in gas chromatography-electroantennogram detection (EAD) studies, were tested in field bioassays as attractants for a Catocheilus thynnine wasp. Two of these compounds, (3,5,6-trimethylpyrazin-2-yl)methyl 3-methylbutanoate and 2-(3-methylbutyl)-3,5,6-trimethylpyrazine, were attractive to male wasps. Additionally, the semiochemical 3-(3-methylbutyl)-2,5-dimethylpyrazine, a close analogue to 2-(3-methylbutyl)-3,5,6-trimethylpyrazine, identified in five other species of thynnine wasps, was equally active. The three remaining compounds from D. livida, which were EAD-active against Catocheilus, did not attract the insects in field trials. It is interesting that two structurally similar compounds induce similar behaviours in field experiments, yet only one of these compounds is present in the orchid flower. Our findings suggest the possibility that despite the high specificity normally characterising sex pheromone systems, the evolution of sexual deception may not be entirely constrained by the need to precisely match the sex pheromone constituents and blends. Such evolutionary flexibility may be particularly important during the early stages of speciation.
authors.affiliation: Research School of Chemistry, The Australian National University, Canberra ACT 0200, Australia. bjorn.bohman@anu.edu.au.|Research School of Biology, The Australian National University, Canberra ACT 0200, Australia. bjorn.bohman@anu.edu.au.|School of Chemistry and Biochemistry, The University of Western Australia, Crawley WA 6009, Australia. bjorn.bohman@anu.edu.au.
authors.forename: Bjorn
authors.initials: B
authors.lastname: Bohman
authors.affiliation: Research School of Biology, The Australian National University, Canberra ACT 0200, Australia. rod.peakall@anu.edu.au.|School of Chemistry and Biochemistry, The University of Western Australia, Crawley WA 6009, Australia. rod.peakall@anu.edu.au.
authors.forename: Rod
authors.initials: R
authors.lastname: Peakall
keywords: Catocheilus; Drakaea; attractant; semiochemical; sexual deception