Patterns of floral evolution of four Asteraceae genera (Senecioneae, Blennospermatinae) and the origin of white flowers in New Zealand

Two parsimony analyses based on morphological data of the subtribe Blennospermatinae (Asteraceae, Senecioneae) were performed to generate a hypothesis for the phylogenetic relationships within the subtribe, which comprises four genera and 27 species of both radiate and disciform genera distributed around the Pacific Rim. Heterogeneity of the group is concomitant with coding problems such as absence of organs leading to inapplicable states, also termed missing entries. Morphological data were therefore coded by two differing methods: (1) using the separate state ''absent'' or (2) using the state ''inapplicable.'' Substantial support for Blennospermatinae monophyly was obtained. A well-supported sister-group relationship, based on floral characters, was established between the two genera Biennosperma and Ischnea. Their ancestor evolved a specialized type of tubeless ray florets and male disc florets. These two genera are confined to the New World and to New Guinea, respectively. Their sister taxon is the monotypic North American genus Crocidium, and its status as a separate genus was supported. Abrotanella is a genus of 19 species confined to alpine habitats in the Southern Hemisphere. Monophyly and the isolated position of Abrotanella was strengthened. One clade of the genus has evolved functionally male central florets with a progressing trend toward cypsela reduction. Different floral colors have evolved in Abrotanella, and the deep yellow color found in the other genera is lost. Among the flowering plants confined to New Zealand, there is a remarkably high ratio of white-flowered species. Results of this study indicate that the white-flowered capitulum is a derived character within Abrotanella originating in New Zealand. A purple-flowered capitulum, also restricted to Abrotanella, is a repeatedly evolved apomorphic character found in species confined to southern South America and the sub-Antarctic Campbell and Auckland islands.