Variation in the Eucalyptus globulus complex revisited

Abstract

Patterns of variation in the Eucalyptus globulus Labill. complex are reassessed by combining capsule measurements from an earlier study with recent collections, mainly of subspecies globulus. Four groups of populations are apparent and can be ascribed to the four subspecies maidenii, pseudoglobulus, bicostata and globulus. Intergrade populations between the latter three subspecies are widespread and mainly occur in the Otway Ranges and west Gippsland. There is a continuum in capsule morphology between the three-fruited subspecies, pseudoglobulus and bicostata. Subspecies globulus intergrades with these three-fruited intermediates. Three-fruited intergrade populations occuning north and south of the range of core pseudoglobulus can be differentiated and probably represent intergrades between pseudoglobulus and bicostata and between pseudoglobulus and globulus respectively. Reports of bicostata in the Furneaux Group and southern Victoria are thus probably erroneous and result from convergence in capsule morphology. The previously described taxon E. stjohnii (R. T. Bak.) R. T. Bak. is part of the continuum between subspecies pseudoglobulus and bicostata, but closer to pseudoglobulus. Populations phenotypically intermediate between and significantly different from globulus and the three-fruited intergrades are highly variable and occur in western Tasmania, on the northern end of Flinders Island, in the Otway Ranges and in west Gippsland. An isolated population on Rodondo Island is highly variable and has closest affinities to pseudoglobulus despite being within the geographical range of core globulus. The population from King Island is intermediate between the Otway phenotype and core globulus. The climatic regimes of the subspecies are markedly different and most three-fruited and globulus intergrade populations have closer climatic affinities to pseudoglobulus and globulus respectively. Hypotheses relating to the origin of the pattern of variation in E. globulus are discussed.