A cladistic and biogeographic analysis of Philotheca (Rutaceae) and allied genera

© 2001 Dr. Michael J. BaylyThis thesis considers the relationships, classification and historical biogeography of the related Australian endemic flowering plant genera Philotheca, Eriostemon and Crowea (family Rutaceae, tribe Boronieae). It focuses mostly on relationships within and between these genera, but also considers the relationships of these groups to other members of the tribe Boronieae, particularly the small genera Geleznowia and Drummondita. It includes a brief appraisal of the species-level taxonomy of Philotheca, Eriostemon and Crowea, a survey of morphological characters, a survey of leaf phenolic compounds, and a series of cladistic and biogeographic analyses. The appraisal of species-level taxonomy identified terminal taxa suitable for use in cladistic analyses, and has resulted in the recognition of one new species (Philotheca sporadica) and three new subspecies (P. myoporoides subsp. brevipedunculata, subsp. euroensis, and subsp. obovatifolia, as well as a recommendation to reinstate one species (Eriostemon banksii, which was previously reduced to subspecific status under E. australasius). The survey of morphological variation identified 108 morphological characters, 99 of which are potentially useful in the assessment of relationships, and nine that are unique to single terminal taxa. The survey of leaf phenolics was based on two-dimensional paper chromatography, and the chromatographic properties and distributions of 26 compounds are reported. Twenty-three of these compounds are potentially useful in the assessment of relationships, and three are unique to single terminal taxa. Assessment of the higher-level relationships of Philotheca, Eriostemon and Crowea (to each other and to other taxa of Boronieae) was based on reappraisal, and re-analysis, of a previous phylogenetic analysis (Armstrong 1991). This reappraisal was based on a limited set of morphological characters, and used genera, sections within genera, and some species as terminal taxa. In general higher-level relationships of the three genera were either poorly resolved or poorly supported. A close relationship of Drummondita to Philotheca sect. Philotheca was supported, but a close relationship of Geleznowia to this group (as has recently been proposed) was not. A series of subsequent analyses of relationships within Philotheca, Drummondita, Eriostemon and Crowea employed a larger set of morphological and phenolic characters (in various combinations), and used species, subspecies and varieties as terminal taxa. Character state transformations were polarised using Crowea as an outgroup to Philotheca, Drummondita and Eriostemon, and vice versa. This assignment of ingroup/outgroup relationships was based on an a posteriori decision, given the lack of a well-supported higher-level phylogeny for the group. These subsequent analyses provided good support for the monophyly of each of Crowea, Philotheca sect. Erionema, P. sect. Corynonema, P. sect. Cyanochlamys, Eriostemon, Drummondita, and a group comprising both Drummondita and P. sect. Philotheca. Philotheca sect. Philotheca was only supported as monophyletic in some analyses. Relationships among these groups were not unequivocally resolved, but the monophyly of Philotheca, as currently circumscribed, was not supported. The biogeographic analyses used the method of subtree analysis and considered the historical relationships of areas in south-western and eastern Australia. The pattern or area relationships was not unequivocally resolved, with some areas showing multiple relationships. The results of these analyses are compared with those from other studies on Australian biogeography. A general historical scenario for the differentiation of taxa and areas is discussed