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Systematics Section / ASPT

Borsch, Thomas [5], Müller, Kai [5], Hilu, Khidir W. [3], Soltis, Douglas E. [2], Soltis, Pamela S. [1], Quandt, Dietmar [4], Löhne, Cornelia [5], Worberg, Andreas [5], Wanke, Stefan [4].

The tree of angiosperms and microstructural changes in the matK gene.

The chloroplast gene matK provides phylogenetic signal not only for resolving relationships within and among genera of plants but also at much deeper levels. Recent studies using matK sequences yielded a highly resolved and well supported phylogeny for angiosperms as a whole, and revealed that the matK coding region contains numerous indels, generally involving multiples of three nucleotides. We analyzed patterns of microstructural changes and assessed signal inherent to indels in the matK coding region from a dataset of 400 taxa from across angiosperms. Frame shift mutations only occur close to the end of the coding region where they may have the least effect on protein structure. In rare occasions, nucleotides in multiples of three appear to be deleted out of frame without affecting the amino acid sequence beyond the deleted codons. Most microstructural changes are simple sequence repeats of one to 5 codons. Indels with overlapping positional extension are less common than in many non-coding regions. We used a simple coding strategy that makes use of unordered binary characters. For comparative purposes, we also employed a multistate character-approach, which required asymmetrical matrix characters in about one third of the cases. Indel information considerably increased resolution and support for many nodes in the angiosperm tree. Many indels of varying length proved to be synapomorphic for angiosperm orders in both basal and derived positions of the tree, such as Nymphaeales and Lamiales. On average, indels in matK were less homoplastic than substitutions. Homoplasy of indels was not correlated with their lengths but rather depends on the position within the gene, hinting at a primary role of structural constraints on length mutational events.

1 - University of Florida, Department of Natural History, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
2 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
3 - Virginia Tech, Plant Pathology, Physiology and Weed Science, 410 Price Hall, Blacksburg, Virginia, 24061-0331, USA
4 - Technische Universität Dresden, Botanisches Institut, Zellescher Weg 22, Dresden, D-01062, Germany
5 - Rheinische Friedrich-Wilhelms-Universität Bonn, Nees-Institut für Biodiversität der Pflanzen, Meckenheimer Allee 170, Bonn, D-53115, Germany

angiosperm phylogeny
microstructural changes
molecular evolution.

Presentation Type: Paper
Session: 58-4
Location: Cottonwood B (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 2:15 PM
Abstract ID:408

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