The Relationships of the Southern African Proteaceae as Elucidated by Internal Transcribed Spacer (ITS) DNA Sequence Data

Abstract

The Proteaceae of southern Africa are a major and defining component of the Cape Floral Kingdom. An accurate and predictive classification of these plants will contribute towards our knowledge of their biogeography, ecology, conservation and horticultural value. This study utilises DNA sequence data of the internal transcribed spacer (ITS) region to elucidate relationships of the genera and species of Cape Proteaceae. Three different phylogenetic analyses were conducted using maximum parsimony on three different data sets, and a neighbor joining (NJ) analysis was also carried out on one of these data sets. Alignment of the sequences proved to be problematic in some regions, and thus one analysis excluded these problematic characters. All analyses resolve Protea and Faurea as sister genera, but the relationships of this group to the remainder of the subfamily Proteoideae are not clear. The remaining genera form a well-supported clade, the "Cape Clade", which is sister to two Australian genera, Isopogon and Adenanthos. All analyses resolve Leucadendron as sister to the rest of this clade. Most analyses resolve Mimetes, Orothamnus, Leucospermum and Diastella as a clade (the MOLD clade), and indicate that the latter three genera are artificial, as Diastella and Orothamnus are embedded within Mimetes. A second clade comprising Sorocephalus, Spatalla, Paranomus and Vexatorella is also retrieved by the analyses presented here (the SSPV clade), and results indicate that the present generic delimitation between Sorocephalus and Spatalla is spurious, and that Vexatorella is a specialised lineage within Paranomus. The precise relationships of Serruria are not resolved with any confidence.