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Phylogeny of Stephanomeria and related genera (compositae–lactuceae) based on analysis of 18S–26S nuclear rDNA ITS and ETS sequences
Author(s) -
Lee Joongku,
Baldwin Bruce G.,
Gottlieb L. D.
Publication year - 2002
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.89.1.160
Subject(s) - biology , monophyly , taxon , clade , botany , exigua , internal transcribed spacer , perennial plant , phylogenetic tree , zoology , spodoptera , gene , recombinant dna , biochemistry
A phylogenetic analysis of DNA sequences from the internal transcribed spacer (ITS), the external transcribed spacer (ETS), and the 5.8S regions of 18S–26S nuclear rDNA from all diploid species of Stephanomeria and related genera shows that Stephanomeria does not include either Munzothamnus blairii (previously S. blairii ) or Pleiacanthus spinosus (previously S. spinosa ). Without these two taxa, Stephanomeria is a well‐supported (100% bootstrap), monophyletic group of ten perennial and six annual species. Munzothamnus blairii and Pleiacanthus spinosus , both now considered members of monotypic genera, had been placed in Stephanomeria primarily because they have the same chromosome number as Stephanomeria and similar pollen surface features, but many disparities were ignored in previous classifications. Within Stephanomeria , an unsuspected sister relationship was detected between the montane S. lactucina and coastal S. cichoriacea . A second clade contained all the annual taxa and five of the perennial species. Among the annuals, strong bootstrap support was obtained for the previously recognized relationships between S. diegensis and S. exigua (98%) and between S. malheurensis and its progenitor, S. exigua subsp. coronaria (96%). Among the five perennial species that constitute a clade with the annuals, the recently described S. fluminea was shown to be sister to S. runcinata , and both of them were closely allied to S. tenuifolia and S. thurberi . The clade including the annuals (and five of the perennial species) was subtended by perennial lineages and pairwise divergence values among the annual taxa were much lower than among the perennial taxa as a group (though not too different than among the perennials in the same clade). The annuals probably originated recently within the genus.