Phylogeny and biogeography of southern hemisphere high-mountain Cardamine species (Brassicaceae)

Abstract

The biogeography and phylogenetic relationships of Southern Hemisphere Cardamine L. species were analysed using nuclear rDNA ITS and cpDNA (trnL intron, trnL-F spacer) sequences. The analyses indicate that the montane species from Australia and New Zealand (C. corymbosa Hook.f., C. lilacina Hook. and C. debilis Banks ex DC.) are closely related to the South American C. glacialis (Forster) DC. Low sequence divergence between C. glacialis and the Australian and New Zealand species suggests relatively recent (less than 500 000 years ago) long-distance dispersal from South America to Australasia, or vice versa. The relationship of the New Guinean species, C. keysseri O.E.Schulz and C. africana L., to the Australian species remained unresolved. Accessions of the high-mountain, pan-continental species C. africana from Africa, South America and New Guinea differed widely in their positions on both the ITS tree and the cpDNA tree, suggesting a polyphyletic origin. The East African high-mountain species C. obliqua Hochst. grouped with European species on the cpDNA tree. The African species, C. trichocarpa Hochst., formed a sister group to all the other Cardamine species analysed.