Patterns of Variation in the Seedling Leaf Oils of Eucalyptus urophylla, E. pellita and E. scias

The volatile leaf oils of glasshouse-grown plants representing natural populations of E. urophylla S.T.Blake, E. pellita F.Muell. and E. scias L.Johnson from the Lesser Sunda Islands, Australia, Papua New Guinea and Irian Jaya were examined for patterns of variation and relationships. The steam distilled oils of the three species were found to be largely monoterpenoid in character and similar qualitatively but variable quantitatively. The relative proportions of α-terpinyl acetate, 1,8-cineole, β-pinene, caryophyllene, α-phellandrene and p-cymene provided good discrimination between species and provenances. The mix of compounds and relatively low yields were such that the oils have no commercial potential. Principal component analysis of oil compositional data revealed groupings of populations consistent with contemporary thinking on the systematics of this complex. The four populations of E. urophylla from Wetar Island included in this study emerged as a group distinct from the main cluster of populations of that species. There was some support in the data for the distinction of high-elevation populations of E. urophylla from eastern Timor from other populations of the species and for the separation of E. scias from E. pellita, although the data, based on limited sampling, was inconclusive. Patterns in the oils of Cape York, Papua New Guinea and Irian Jaya provenances of E.pellita were variable. Evidence from other characters (e.g. adult morphology) will be needed to support the hypothesis that the Cape York and New Guinea populations of E. pellita constitute a new taxon.