Saintpaulia 5S-NTS nrDNA

 

Data: 24 aligned 5S-NTS sequences; 23 sequences of Saintpaulia and one sequence of Streptocarpus (outgroup). GENBANK accession numbers are indicated after each taxon name in the matrix. Gaps are indicated with "-"; "?" indicates missing data.

Matrix type: Parsimony jackknife format, text-only.

Reference: Lindqvist, C. & V. A. Albert (in press). Phylogeny and conservation of African violets (Saintpaulia: Gesneriaceae): new findings based on nuclear ribosomal 5S non-transcribed spacer sequences. Kew Bulletin.

Summary of results: The species of the genus Saintpaulia, also known as African violets, are restricted to the Eastern Arc Mountains and the coastal lowlands of East Africa. The 20 described species of Saintpaulia are all narrowly distributed, rare and habitat specific. Loss of natural habitat is a major threat to their survival. Species delimitation within the genus has proven difficult and previous studies have been based on cultivated clones only. Therefore, problems arise when efforts are made to determine conservation priorities. Previous phylogenetic analysis of Saintpaulia based on nrDNA internal transcribed spacer (ITS) showed species within Saintpaulia to be poorly distinguished at the molecular level. For this study the phylogeny, biogeography, and conservation prioritization of Saintpaulia was investigated based on new field collections and cladistic analyses of nucleotide sequences from the 5S nuclear ribosomal DNA non-transcribed spacer (5S-NTS). The results provided a single most parsimonious tree separating Saintpaulia into four well-supported major clades: 1) the basal most clade represented by taxa from the Ulugurus Mts., S. pusilla and two S. goetzeana populations; 2) S. teitensis from the Taita Hills; 3) S. brevipilosa and S. cf. velutina from the Nguru Mts.; and 4) a large group of taxa from the Usambara Mts. and lowland regions. Although in overall agreement with the previous phylogenetic study based on ITS sequences, the present study provided significantly better topological resolution. High sequence divergence was found among taxa in the basal clades compared to the short branch lengths within the unresolved Usambara/lowland clade. Not included in this study are reported populations of S. goetzeana from the Nguru Mts. and of S. pusilla occurring in the Ukaguru and Nguru Mts. Since these taxa and S. teitensis from Teita Hills occupy the most basal positions of the Saintpaulia tree, the involved areas could all have been part of a larger ancestral and previously continuous area of distribution. Indeed, the Nguru Mts. hold the highest genetic and taxic diversity of Saintpaulia. Two to three of the four major clades are found in these mountains representing both basal and derived taxa. It is therefore suggested that the Nguru Mts. be afforded highest priority in the conservation of Saintpaulia genetic and morphological diversity. Furthermore, it is suggested that conservation priority should be directed at Kenyan lowland taxa, which are genetically distinct and could be segregant outposts of a larger Usambara/lowland metapopulation of Saintpaulia. Despite the high species diversity in the Usambara Mts, no conclusions on conservation prioritization could be made because of very little phylogenetic structure in this region.

Contact person: Charlotte Lindqvist

Date posted on WWW: 06/22/99

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