Venom alkaloid chemistry of Australian species of the Monomorium rothsteini complex, with particular reference to taxonomic implications.

A comparison of the morphology and of the venom alkaloids of the Australian Monomorium rothsteini complex was undertaken. These ants were collected in Australia from western New South Wales, northern Queensland, and northern Northern Territory. Additionally, samples from the M. sordidum complex and M. carinatum complex were examined. Thirteen previously described trans-2,5-dialkylpyrrolidines were detected in these ants, along with the novel trans-2-ethyl-5-[(Z)-tridec-4-enyl]pyrrolidine (6), whose structure was confirmed by synthesis. The extent of variation and the correlation observed in the morphology and venom chemistry in M. rothsteini samples is very strongly indicative of multiple species in this complex. The presence and location of the C==C bond in 6 reinforces the remarkable structural similarity of the 2-ethylpyrrolidines in these Monomorium species to the 2-methylpiperidines in the venoms of many Solenopsis species, and may represent convergent evolution of biosynthetic processes in different genera of solenopsidine ants.