Globally grown, but poorly known: species limits and biogeography of Gazania Gaertn. (Asteraceae) inferred from chloroplast and nuclear DNAsequence data
Gazania is a popular horticultural subject worldwide and comprises 16 species, all from southern Africa.However, species delimitation is difficult as many species are morphologically variable. Here we present a phylogenetic analysis of 15 species of Gazania, , based on DNA sequence data from four non-coding chloro- plast regions (trnL-intron, trnL - trnF spacer, psbA - trnH spacer, rps16 intron) and two nuclear spacers (InternalTranscribed Spacer, ITS; partial External Transcribed Spacer, ETS). The phylogenies derived from the plastidand nuclear datasets were not entirely congruent, but data combination was undertaken. Of the 15 speciessampled, only 7 are supported as monophyletic. Most of the remaining taxa form a large, poorly resolved cladecorresponding to a large, morphologically variable species complex. Using a range of ITS mutation rates, thediversification of the genus is estimated to have begun approximately 6.6 mya. The phylogeny, in conjunc-tion with the distribution patterns, suggests that this genus arose in the semi-arid to arid Richtersveld/Namibregions of South Africa and Namibia. Keywords: Asteraceae, Gazania, molecular dating, phylogeny, southern Africa, species delimitation.
Taxon
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Species limits and biogeography of Gazania.pdf | 1.56 MB |