Abstract
Considerable controversy exists with regard to the proper delimitation of Cymopterus (Apiaceae subfamily Apioideae) and its relationship to the other perennial endemic umbellifers of western North America. Previous molecular systematic studies using nuclear (rDNA ITS) and, for subsets of taxa, plastid (rps16 intron and trnF-trnL-trnT) DNA sequences have revealed that the genus Cymopterus is polyphyletic, with its species inextricably linked with those of Aletes, Lomatium, Musineon, Oreoxis, Pseudocymopterus, Pteryxia, Tauschia, and several other genera of the region. Herein, in an effort to increase resolution of relationships, we procured rps16 intron sequence data from 74 accessions of Cymopterus and its allies so that ITS and intron matrices are available for the same set of 129 taxa. These data matrices were analysed, separately and in combination, using maximum parsimony and (or) maximum likelihood methods. For those trees exhibiting the greatest resolution, the results revealed that the perennial, endemic apioid genera of North America (north of Mexico) comprise a weakly supported monophyletic group, with Angelica constituting its sister lineage. Cymopterus is confirmed as highly polyphyletic. The rps16 intron yielded substantially fewer parsimony informative characters than those of the ITS region and when analysed, separately or in combination, with ITS data, resulted in trees of poor resolution. Only one previously identified species group of Cymopterus is supported as monophyletic; this group coincides with section Phellopterus, and is recognised by its showy, basally connate bractlets. Many other genera endemic to western North America appear to be highly artificial assemblages of species that will likely be abandoned in any revised system of umbellifer classification.
Highlights
The genus Cymopterus Raf., the spring-parsleys, comprises some 40 herbaceous perennial taxa restricted primarily to xeric habitats in western North America (Kartesz 1994, Hartman 2000)
The dorsal ribs may be wingless and, in such cases, the fruits resemble those of Lomatium (Cronquist 1997, Downie et al 2002)
Much confusion exists with regard to the proper delimitation of Cymopterus and its relationship to the other indigenous umbellifers of western North America (Jones 1908, Mathias 1930, Theobald et al 1963, Evert and Constance 1982, Weber 1984, Gilmartin and Simmons 1987, Cronquist 1997)
Summary
The genus Cymopterus Raf., the spring-parsleys, comprises some 40 herbaceous perennial taxa restricted primarily to xeric habitats in western North America (Kartesz 1994, Hartman 2000). Much confusion exists with regard to the proper delimitation of Cymopterus and its relationship to the other indigenous umbellifers of western North America (Jones 1908, Mathias 1930, Theobald et al 1963, Evert and Constance 1982, Weber 1984, Gilmartin and Simmons 1987, Cronquist 1997). Previous studies have demonstrated the utility of the rps intron for phylogeny estimation in Apiaceae (Downie and Katz-Downie 1999, Lee and Downie 2000, Downie et al 2000, 2002), and it was hoped that this region could supply the information required to increase resolution and branch support of the resulting phylogenetic estimate
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