Ancient allopolyploidy in the everlasting daisies (Asteraceae: Gnaphalieae): Complex relationships among extant clades

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Abstract:

Phylogenetic analyses have suggested that the everlasting daisy tribe Gnaphalieae colonized the globe repeatedly and rapidly from southern Africa. However, both the circumscription of monophyletic groups of “out of Africa” Gnaphalieae genera and the identification of their sister groups in southern Africa has proved difficult. We have analysed sequences of nrDNA spacers (ITS, ETS), cpDNA (ndhF, trnL intron, trnL-trnF intergenic spacer, trnK intron), and low-copy nuclear markers to examine selected relationships within the crown radiation of the tribe. We focused on relationships among two putative clades suggested by previous studies and a representative sampling of genera endemic to Australasia. Incongruities between nrDNA and cpDNA trees are frequent and some involve robustly supported clades. However, trees generated for two low-copy nuclear markers are largely congruent with each other but imply that allopolyploidy preceded the radiations of at least four separate extant lineages within the tribe, one largely or entirely restricted to Australasia, one almost global, and two still poorly sampled. Collectively, these four putative allopolyploid lineages may account for more than half of the described species diversity of the tribe.

Keywords: HYBRID SPECIATION; HYBRIDIZATION; LOW-COPY NUCLEAR GENES; PALEOPOLYPLOIDY; PGIC; PHYLOGENY

Document Type: Research Article

Publication date: June 1, 2011

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