Variation in Australian populations of Halfordia kendack s.l. (Rutaceae): evidence from leaf essential oils

Abstract

The leaf oils of Halfordia kendack (Montrouz.) Guillaumin s.l. from locations throughout its range in Australia were investigated to ascertain if the disjunct nature of the species' distribution affected their composition and whether any variation detected supported the recognition of a second species (H. scleroxyla F.Muell.). While three groups of populations could be classified on the basis of leaf oil composition, these groups were not associated with geographic locality or altitudinal range and habitat. It was found that plants from low altitude sites in north Queensland all produced leaf oils that contained the aromatic ethers methyl eugenol and elemicin in variable amounts, included in an otherwise terpenoid oil. Plants from the other three areas examined; north Queensland montane sites, south-east Queensland low altitude and south-east Queensland montane sites, all produced leaf oils which were terpenoid in nature and contained no aromatic ethers. This lack of correlation in leaf oil composition with locality or habitat would lend support to the proposition that Halfordia exists in only one variable species in Australia.