Systematics/Phytogeography / Taxonomie/ Section
Sytsma, Kenneth J. , Williams, Cody , Hahn, William James .
Phylogenetics and character evolution within Clarkia (Onagraceae).
Phylogenetic relationships were estimated for 39 of the 42 species of Clarkia (Onagraceae) representing all recognized sections and subsections in the genus using nuclear rDNA ITS and cpDNA rpS16, rpL16, trnD-T and trnL-F sequences. The topologies of trees obtained through MP, ML and Bayesian analyses were very similar. Although partition homogeneity tests performed on the complete data set resulted in a significant differences between nuclear and cpDNA partitions, these differences disappeared with removal of some polyploidy taxa. Polyploid taxa are resolved as closely related to one or both of the putative parental taxa. Although these trees are largely similar to the latest phylogenetic tree of Clarkia based on duplicated genes of nuclear pgi, there exists some strong discordance of species relationships between both nuclear ITS and cpDNA with nuclear pgi. Recovered phylogenies were used to analyze chromosome number and genome size evolution under ML and Bayesian frameworks. Best-supported estimates of relationships indicate that the diploid n=8,9 sections and their polyploid derivatives form a monophyletic group while the n=7 sections and their derivatives form a paraphyletic grade. In all but one species examined, genome sizes of polyploid taxa are less than the sum of the two postulated parental species suggesting genome size loss following allopolyploidy. Three groups are recognized with relatively stable diploid genome sizes: 1) a clade of sections Eucharidium + Clarkia, with diploid genomes ca. 2-3 times larger than those of the outgroup Oenothera, 2) sections Rhodanthos and Myxocarpa with all species but two (C. arcuata and C. virgata) possessing genomes ca. one and a half to two times the size of the outgroup, and 3) a clade including all remaining taxa with all but two species (C. bottae and C. modesta) with genome sizes comparable to those found in the outgroup.
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1 - University of Wisconsin Madison, Department of Botany, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
2 - University of Wisconsin, Madison, Department of Botany, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
3 - Georgetown University, Georgetown College, 108 White-Gravenor, Po Box 571003, Washington, DC, 20057-1003, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Room 1/Woodward
Date: Monday, July 28th, 2008
Time: 11:15 AM