Natural Hybridization and Morphometric Relationships Between Three Mallee Eucalypts in the Fitzgerald River National Park, W.A

Abstract

The suspected occurrence of natural hybridization between Eucalyptus preissiana Schau, and E. Buprestium F. Muell, near West Mount Barren was investigated through a study of morphometric and reproductive parameters in allopatric and sympatric populations of these species. While E. Preissiana and E. buprestium were morphometrically distinct in allopatry, a small number of intermediate individuals occurred in one of the two sympatric populations examined. These intermediates set less fruit per plant than the parental species on average, a fact consistent with the hypothesis that they were hybrids showing partial F2 breakdown. The demonstration that New Holland honeyeaters (Phylidonyris novae-hollandiae) carried pollen of both parental species in a sympatric population was interpreted as further evidence in support of the occurrence of hybridization. The possible hybrid status of E. chrysantha Blakely & Steedman was investigated through determining its morphometric relationships in a multivariate analysis of E. sepulcralis F. Muell., E. Preissiana and E. buprestium. E. chrysantha was intermediate between E. sepulcralis and E. preissiana, and distinguishable from E. preissiana-E. buprestium hybrids in this analysis. The taxonomic and evolutionary implications of the study are discussed.