A high elevation ancestry for the Usambara Mountains and lowland populations of African violets (Saintpaulia, Gesneriaceae)

A cladistic analysis of 5S nuclear ribosomal DNA non-transcribed spacer (5S-NTS) sequences representing 55 Saintpaulia accessions and one Streptocarpus outgroup taxon is presented. All formally described and potential Saintpaulia taxa are included except for S. 'mafiensis' and the possibly extinct S. inconspicua. Most notably, Saintpaulia shumensis, the highest elevation species in the Usambara Mountains, is resolved, albeit with marginal parsimony jackknife support, as the sister taxon to all remaining members of the Usambaras/lowland clade, which is otherwise poorly structured. It is hypothesized that Saintpaulia shumensis may show a relictual distribution in the Usambaras, as there appears to be a phylogenetic trend from higher to lower elevation among the major clades of Saintpaulia. Further issues discussed include the implications of intra-individual nucleotide polymorphism and the narrow genetic basis for drastic differences in trichome morphology, a cardinal characteristic for Saintpaulia taxonomy.