Phylogeny of the Proteaceae based on atpB and atpB-rbcL intergenic spacer region sequences

Abstract

Parsimony analyses were conducted for 46 genera representing all subfamilies and tribes within Proteaceae using two chloroplast sequences: the gene atpB and the noncoding spacer region between atpB and rbcL. The spacer region was more variable than atpB and provided insertion and deletion data as well as nucleotide substitutions. The atpB and spacer region data sets were highly congruent (as indicated by the partition homogeneity test) and were analysed separately and combined. Both unweighted and weighted character states (3 : 1 correction for transition bias) for the atpB data resulted in very similar strict consensus trees. In addition, the large subfamilies Proteoideae and Grevilleoideae were analysed separately, using appropriate outgroups determined by the analyses with complete sampling. The results from the combination of data were better resolved and supported than the results from each separate data set, although the Grevilleoideae were highly unresolved in all analyses. Most subfamilies in the Proteaceae were essentially monophyletic, but most tribes and subtribes were not. Bellendena is weakly supported as the sister group to all remaining members of the Proteaceae. Monotypic Eidotheoideae is well supported as a member of Proteoideae. Carnarvonioideae and Sphalmioideae are strongly supported as closely allied to the Grevilleoideae, but their positions in relation to this subfamily are unresolved. Other unusual alliances supported by our molecular data are: Isopogon–Adenanthos–Leucadendron–Protea, Petrophile–Aulax, Cardwellia–Euplassa–Gevuina, and Opisthiolepis–Buckinghamia–Grevillea. The tree resulting from the combined data showed limited congruence with morphological characters (flower pairs, stylar pollen presentation, and ovule number). Congruence with chromosome number was minimal, but our tree does support previous hypotheses of multiple aneuploidy and chromosome doubling events. The African and South American genera included in our analysis are dispersed among various clades with taxa from Australia and Asia, suggesting a former Gondwanian distribution for Proteaceae.