A phylogenetic study of some representatives of the genus Pentaschistis

[摘要] English: The genus Pentaschistis (Nees) Spach consists of 68 species and is endemic toAfrica, with 57 species being indigenous to South Africa and 40 species endemic (GibbsRusseIl et al. 1990).To date, the chromosome number of 30 species have been reported, as well as thesequences of the rpoC2 gene of two species and the ITS region of one species.In this study, seventeen specimens were cytogenetically examined. The polyploidlevels ranged from diploid (n = x = 7) to 14-ploid (n = 7x = 49). Two species wereexamined for the first time, namely: P. capensis (diploid) and P. veneta (tetraploid). Newpolyploid levels were also observed for P. viscidula (tetraploidy), P. densifolia(octaploidy), P. rupestris (decaploidy & 14-ploidy) and P. tortuosa (octaploidy).Due to the fact that no, or very few, multivalents were observed, we concludedthat the species are alloploids or segmental alloploids tending towards alloploidy. Themorphological groupings (Linder & Ellis 1990a) could unfortunately neither be supportednor rejected by cytogenetic evidence alone, therefore cytogenetics was used inconjunction with molecular data to determine the phylogeny.The fragment patterns obtained from RAPDs were used to calculate the geneticdistances. A high degree of variation was observed within and between the morphologicalgroups. Cladograms were obtained with the computer programs PAUP and Hennig86,and PAUP gave the most parsimonious cladogram. The resolutions of these cladogramswere, however, not good, therefore DAFs was performed.Again PAUP and Hennig86 were used and again PAUP proved to give the mostparsimonious clado gram. These cladograms gave a clearer indication of the phylogeny ofPentaschistis, but the genetic distances within and between the species again proved to behigh.The ITS} region was sequenced and aligned separately with Clustal W and Malign.These cladograms indicated a close alliance between P. eriostoma and P. curvifolia.The three data sets were combined and a cladogram with much better resolutionwas obtained. The morphological data was included and had a minor influence on thephylogeny. This cladogram also indicated a sister relationship between P. eriostoma andP. curvifolia.Current data suggest that P. eriostoma could well have developed through thehybridisation of P. curvifolia and that both P. eriostoma are correctly grouped withPentaschistis. The combined analysis also indicate that the morphological groupings ofLinder & Ellis (1990a) is somewhat supported by phylogeny.

[发布机构] University of the Free State