Molecular phylogenetics and morphological evolution in Cunonieae (Cunoniaceae)

The Cunonieae are the largest tribe in the flowering plant family Cunoniaceae and include the widespread genus Weinmannia. This study aims to understand phylogenetic relationships within Cunonieae by using DNA sequences in a parsimony-cladistic analysis. Sequenced loci included the internal transcribed spacers (ITS-1 and ITS-2) of,nuclear ribosomal DNA, and the trnL intron and trnL-F spacer of chloroplast DNA. Primer and taxon-specific amplification of non-orthologous ITS-2 copies made it necessary to exclude the ITS-2 data, but otherwise the nuclear and chloroplast data sets were congruent. The results place Vesselowskya as the sister genus to other Cunonieae and support the monophyly of Pancheria, Cunonia, and all five sections of Weinmannia, but do not indicate how these groups are related. The monophyly of Weinmannia sect. Weinmannia is upheld, with W trichosperma from temperate forests of South America and W tinctoria from the Mascarene Islands placed basal to a large clade of tropical American species. Although morphological data maintain the monophyly of Weinmannia, this is neither verified nor statistically refuted by the molecular data. Likewise, Cunonia, with one isolated South African species, has only weak molecular support but clear morphological synapomorphies. Lack of support for relationships among major clades within Cunonieae makes it difficult to suggest patterns of morphological evolution. However, a well-supported phylogenetic hypothesis within Weinmannia sect. Leiospermum is used to discuss heterotopy in inflorescence architecture. Uniquely derived features of the inflorescence are found in the New Caledonian species Weinmannia dichotoma and in the New Zealand species W silvicola and W racemosa. These heterotopic changes involve alternate patterns in the fate of terminal meristems and the arrangement of metamers bearing racemes. In an appendix the correct orthographies and original publications of all five sections of Weinmannia are provided; types are also designated for Weinmannia sections Inspersae and Spicatae in order to validate them.