A phylogenetic analysis of Cunoniaceae

We present a cladistic analysis of genera of Cunoniaceae based on 44 structural characters using Wagner parsimony. A synthetic outgroup based on the attributes of Hamamelidaceae, Rosaceae and Fagaceae was used to polarize character states and root resulting cladograms. In all of the resulting cladograms, a clade consisting of Gillbeea, Brunellia, Spiraeanthemum, and Aistopetalum formed the sister group of the rest of the Cunoniaceae. The continued recognition of Brunellia in a monogeneric family separate from Cunoniaceae was not supported by our results. The hypothesis that apocarpy was secondarily derived within the Cunoniaceae in Brunellia and Spiraeanthemum was supported. The sister group of the above set of taxa shared the derived possession of interpetiolar stipules (although they originated in parallel in the Spiraeanthemum-Aistopetalum group). The group defined by interpetiolar stipules, consisting of the bulk of the Cunoniaceae, includes Eucryphia and Bauera, which have been placed often in monotypic families. Eucryphia is the sister group of a clade defined by bicarpellate gynoecia, which are derived within Cunoniaceae. Bauera is a member of a clade of subshrubs that includes Acrophyllum and Anodopetalum. The southern hemisphere family Cunoniaceae is centered largely in eastern Australia, New Guinea, and New Caledonia with a few genera in southern Africa, Madagascar, and the neotropics. Cunoniaceae have been discussed as including the most primitive members of Rosidae. As such, the family was allied traditionally with Rosaceae and Saxifragaceae s.l. (Baillon 1871; Engler 1928a; Hutchinson 1959; Schulze-Menz 1964; Wettstein 1935). Kalkman (1988), for example, considered Cunoniaceae to be the most plausible sister group of Rosaceae. Ingle and Dadswell (1956) noted the resemblance of wood features among Cunoniaceae, Dilleniaceae and Theaceae. Takhtajan (1969) linked Rosidae to Dilleniales through Cunoniaceae. Recently, similarities have been re-emphasized between Cunoniaceae and certain basal Hamamelidae, particularly Hamamelidaceae (Dickison 1989). Hence, the Cunoniaceae appear positioned at a critical transitional point in the evolution of higher dicotyledonous groups (see also Ehrendorfer 1977; Ehrendorfer et al. 1984) and, therefore, assume considerable phylogenetic importance. Despite the key position of Cunoniaceae for understanding the radiation of higher dicotyledonous groups, numerous questions remain about patterns of character evolution and relationships within the family. This cladistic analysis of the genera of Cunoniaceae addresses these questions. Nineteen to 26 genera generally are circumscribed in the family. They are woody plants with decussate leaves and most have interpetiolar stipules. The decussate leaf arrangement has been hypothesized (Dickison and Rutishauser 1990; Kalkman 1988) to support the monophyly of Cunoniaceae. The genera have diverse inflorescence, flower and fruit forms which have created problems for understanding relationships within the family. A significant problem is the relationship of two problematic genera, Bauera and Eucryphia, to Cunoniaceae. Although often allied with Cunoniaceae (Bausch 1938; Dickison 1978; Hils 1989; Huber 1963; Jay 1968; Patel 1990; Planchon 1854), each is generally placed in a monotypic family. Both Bauera and Eucryphia have a decussate leaf arrangement. Eucryphia has interpetiolar stipules. Until recently, Bauera had been considered exstipulate; however, it has been shown to have paired, free stipules with the opposite leaves at each node (Dickison and Rutishauser 1990; Hils 1989). Dickison and Rutishauser (1990) hypothesized that both Bauera and Eucryphia are nested within Cunoniaceae as