Morphological variation and phylogenetic relationships within Eucalyptus series Subulatae (Myrtaceae) of southern Australia

Abstract

Morphological variation within Eucalyptus series Subulatae, a group of mallee and woodland tree taxa distributed across southern Australia, was assessed by adult and seedling characteristics. A phenetic study included a total of 51 adult morphological characters and 37 seedling characters, which were assessed for 564 individuals representing 163 populations, covering the broad geographical distribution of the series. All taxa included in the series by either Johnson and Hill (1999) or Brooker (2000) were included together with E. angustissima, E. cooperiana, E. falcata and E. salmonophloia, all of which have been at times included in, or considered closely related to, E. ser. Subulatae. The phenetic analyses indicate that the four subseries of Brooker (2000) are morphologically distinct, although their distinctiveness is only evident from seedling characters. The two subseries that Johnson and Hill (1999) recognise (subser. Flocktonianosae and Transcontinentalosae) corresponding to Brooker’s (2000) subser. Decurrentes, are more weakly defined. Southern populations of E. dolichocera are not considered here to belong to this species but rather to belong to a different subseries based on seedling morphology. A phylogenetic analysis of 44 morphological characters and 23 species of E. ser. Subulatae and 24 species from variously related taxa suggest that E. ser. Subulatae may not be monophyletic. Eucalyptus brockwayi and E. salmonophloia are basal to E. ser. Subulatae and all of the other taxa included in the analysis. Within E. ser. Subulatae, subsers Oleaginae and Spirales are both monophyletic. Both the phylogenetic and phenetic analyses strongly suggest that E. brockwayi is unique in several characters, including some not previously recognised, and is best placed in a monotypic series. The position of E. aspersa remains unresolved, but is probably best retained in E. subser. Decussatae. A key to the subseries of E. ser. Subulatae is presented and putative intersubserial, interserial and intersectional hybrids involving the series are cited.