Patterns of variation and relationships in the Eucalyptus Alpina–E. baxteri complex (Myrtaceae) based on leaf volatile oils

Abstract

In the stringybark eucalypts, the baxteri clade consists of E. arenacea, from South Australia and northwestern Victoria, E. baxteri, mainly from the Great Dividing Range of Victoria, and E. alpina, an endemic taxon from the Grampian Ranges of Victoria. Populations of these taxa were sampled from across their geographic and morphological ranges. Phenetic and phylogenetic analyses were undertaken of the leaf volatile oil composition of the sampled plants. On the basis of these analyses, E. arenacea emerges as a cohesive, monophyletic species, while E. baxteri is a variable and probably paraphyletic species. Populations on Kangaroo Island, South Australia, are variable and intermediate, and may represent recent intergradation between the two species. Populations of E. baxteri from the Grampians are distinctive chemically, but not morphologically, within the species. Recent hybridisation between this form of E. baxteri and E. alpina was shown to be occuning within the Grampians. E. alpina is a highly variable taxon, and probably polyphyletic as currently recognised. Three distinct forms were recognised within E. alpina. The first, and most distinctive, is from the southern Serra Range; the second is from the northern Serra Range and Wonderland Range; the third, and most similar to E. baxteri, is from the Victoria Range.