A Phylogenetic Study of Cymopterus and Related Genera (Apiaceae)

Abstract

287 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2003.Considerable confusion exists with regard to the delimitation of Cymopterus and its relationship to other perennial genera of Apiaceae subfamily Apioideae endemic to western North America (north of Mexico). Cladistic analyses of nuclear (rDNA internal transcribed spacer) and chloroplast ( rps16 intron and trnF-trnL- trnT) DNA sequences were carried out for 129 accessions (22 genera) of North American Apioideae to evaluate the monophyly of Cymopterus , and to ascertain its phylogenetic placement among these other genera. To elucidate evolutionary patterns of fruit and other characters and to evaluate their utility in circumscribing genera and major clades, 54 morphological characters were analyzed phylogenetically. Additionally, multivariate analyses were undertaken to examine patterns of morphological variation in three taxonomically controversial species complexes, Cymopterus acaulis, Pseudocymopterus montanus, and Pteryxia terebinthina. Results of the phylogenetic analyses reveal that the perennial endemic apioid genera of North America constitute a weakly supported monophyletic group. Cymopterus is highly polyphyletic, with its species inextricably linked with those of Aletes, Lomatium, Musineon, Oreoxis, Podistera, Pseudocymopterus, Pteryxia, and Tauschia. Oreonana, Orogenia , and Polytaenia, in addition to eastern North American Thaspium and Zizia, are each strongly supported as monophyletic. Low molecular sequence divergence suggests that this group of North American umbellifers underwent rapid radiation, thus resolution of relationships among these taxa remains poor. Optimization of morphological characters onto the molecular-derived trees indicates very few uniquely occurring morphological synapomorphies supporting genera or major clades. Fruit morphological characters, used traditionally to circumscribe genera within the group, are highly homoplastic, and the emphasis placed on them previously has led to highly artificial assemblages of species. The results of multivariate analyses do not support the segregation of infraspecific taxa in Cymopterus acaulis and Pseudocymopterus montanus. The morphological characters used to distinguish these infraspecific taxa are highly variable within the taxa and of little taxonomic value. Based on molecular study, both species are monophyletic. In contrast, Pteryxia terebinthina is not monophyletic, yet the results of the multivariate analyses suggest that its infraspecific taxa are morphologically indistinguishable. A complete reassessment of the generic limits of all western North American Apioideae, and further study of the Pteryxia terebinthina complex, is clearly required.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD