Molecular systematics of the Western Cape genus Serruria Salisb. (Proteaceae L.) based on DNA sequence data

[摘要] ENGLISH ABSTRACT:The Cape Floristic Region (CFR) is situated at the southern tip of Africa and possesses a flora thatis unique amongst the floras of the rest of the world, both in terms of its incredibly high speciesrichness, and its high levels of endemism. Proteaceae, the family to which Serruria belongs, iswidely distributed amongst the landmasses of the southern hemisphere, with its centres of diversityoccurring in Australia and southern Africa.Previous molecular and morphological analyses performed on the South African subfamilyProteoideae have shown Serruria, a CFR endemic, to form a well-supported monophyletic group.Based upon the strong monophyly of Serruria, DNA sequence data were collected for 53 of the 55species from the plastid (rps16 intron, atpB-rbcL intergenic spacer, trnL-F region and psbA-trnHintergenic spacer) and nuclear (internal transcribed spacer region or ITS) genomes in order toinvestigate evolutionary relationships within the genus. Spatalla taxa were used as the outgroup.Both parsimony and Bayesian analyses were carried out on each of these data sets. The resultingtrees were reasonably well resolved. All the Serruria taxa grouped together in a well-supportedclade, except for S. f1ava, which emerged well within the Serruria clade in the analyses of thenuclear genome, but outside the clade in the plastid analyses. It was therefore proposed that thistaxon represents a hybrid. Apart from this case, there was widespread agreement between thetrees reconstructed using data from the two genomes. The plastid and nuclear data were thereforecombined in order to analyse the data sets together.The molecular data does not support most of the groupings proposed by previous authors basedon morphological data. Additionally, in some cases, multiple representatives of species do notgroup together. These specimens probably do not represent monophyletic taxa. Current ideasabout relationships within Serruria are based predominantly on floral characters, and it issuggested that pollinator pressures have led to plasticity in the floral characters.Consequently, it is evident from this study that relationships within Serruria need to be re-examinedin order to determine the patterns of evolution within the genus.

[发布机构] Stellenbosch University