Origin of the Grampians Shining Peppermint ̵1 a New Subspecies of Eucalyptus willisii Ladiges, Humphries & Brooker

Abstract

Adult morphology, seedling morphology and leaf volatile oil composition are described for a peppermint eucalypt (Eucalyptus aff. willisin restricted to the Grampians, Victoria. Populations were compared with E. willisii collected from Mt Richmond and Wilson's Promontory and the ash, E. pauciflora, collected from the Grampians. Three data sets were independently analysed by using multivariate classification and ordination techniques in order to test the hypothesis that introgression has occurred between E. willisii and E. pauciflora in the Grampians.

The hypothesis of introgression was not supported. The Grampians peppermint is a uniform and distinct entity which is not overall intermediate between E. willisii and E. pauciflora. It is typified by large obconical fruit; adult leaves with low oil gland density and a distinctive leaf volatile oil composition; and seedlings which display early intranode development, petiole formation and twisting, and leaves with tapering bases.

The Grampians peppermint has probably evolved from a small founder population of E. willisii (or a common ancestor) that has diverged in isolation. The presence of a few 'ash' characters in the Grampians peppermint is here considered to be due to convergent evolution, in the direction of E. pauciflora. The Grampians peppermint is described as a new subspecies.