Systematics Section / ASPT
Winkworth, Richard C. , Donoghue, Michael J. .
Localized incongruence between molecular data sets highlights
complex evolutionary patterns in Viburnum.
We investigated the phylogeny of Viburnum (Adoxaceae, Dipsacales) using separate and combined analyses of DNA sequence data from two chloroplast (trnK intron and psbA-trnH intergenic spacer) and three nuclear (nrITS and two copies of GBSSI) loci. These analyses confirm (i) the monophyly of some and the non-monophyly of other traditionally recognized taxonomic sections, (ii) the presence of three major supra-sectional lineages within Viburnum, and (iii) the resolution of many species relationships within the major clades. Basal relationships within Viburnum remain uncertain; in particular, the position of the root, relationships among the supra-sectional clades, and the exact placement of several smaller groups. While there is much similarity between gene trees from our various analyses several apparent conflicts provide insights into complex patterns of diversification within Viburnum. In most viburnums the nuclear low-copy number locus GBSSI is represented by two paralogues, however in two clades each of these forms is represented by two distinct sequences. The presence of additional copies appears to be correlated with polyploidy in these lineages; the placement of the homoeologues within gene trees suggesting possible hybrid origins. Analyses of separate nuclear and chloroplast matrices highlighted several areas of localized incongruence. Specifically, (i) the position of Pseudotinus, (ii) species relationships within Pseudotinus, and (iii) relationships among core members of the Lentago clade. At least in the case of Lentago this conflict may reflect homoploid hybrid speciation. Possible explanations for incongruence associated with Pseudotinus are more enigmatic.
1 - Yale University, Department of Ecology and Evolutionary Biology, P.O. Box 208105, New Haven, Connecticut, 06520-8105, USA
nuclear DNA sequence
chloroplast DNA sequence.
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 3:00 PM