Phylogenetic relationships among the perennial, endemic Apiaceae subfamily Apioideae of western North America: additional data from the cpDNA trnF-trnL-trnT region continue to support a highly polyphyletic Cymopterus

摘要

Considerable confusion exists with regard to the delimitation of Cymopterus and its relationship to theother herbaceous, perennial genera of Apiaceae subfamily Apioideae endemic to western North Amer-ica north of Mexico. Previous molecular systematic studies using nrDNA ITS and cpDNA rps16 in-tron sequences have shown that the genus Cymopterus is highly polyphyletic, with its species inextri-cably linked with those of Aletes, Lomatium, Oreoxis, Pseudocymopterus, Pteryxia, and several othergenera of the region. The general lack of resolution of these trees and their overall low branch supportvalues, however, suggested that additional data might be useful to establish monophyly of genera oridentify major clades for further phylogenetic and revisionary studies. In this study, we analyze cpD-NA trnF-trnL-trnT sequence data from 129 accessions of North American Apioideae (representing111 species and 21 genera) using maximum parsimony, maximum likelihood and Bayesian inferencemethods individually and in combination with ITS and rps16 intron sequence data available throughprevious phylogenetic studies for the same set of accessions. While analyses of the trnF-trnL-trnTregion result in maximally parsimonious trees of greater branch support and less homoplasy thanthose generated using either ITS or rps16 intron data sets, greatest resolution of relationships andhighest branch support values are achieved when all DNA regions (representing over 3.5 kb of aligneddata) are considered simultaneously. Three or four new major clades are revealed, yet none of thesecoincide with pre-established groups or traditionally recognized genera. The results obtained continueto suggest that Cymopterus is highly polyphyletic, as are most other genera endemic to western NorthAmerica.