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Abstract Detail

Systematics/Phytogeography / Taxonomie/ Section

Peery, Rhiannon [1], Wilcox, Kevin R. [2], Morton, Cynthia [3], Raubeson, Linda A. [1].

Exploring the utility of the nuclear XDH gene for gymnosperm phylogenetics.

We are examining the phylogenetic utility of the nuclear gene XDH (xanthine dehydrogenase) in gymnosperms. Currently we are in the initial stages of this assessment, amplifying and sequencing XDH in representative taxa to investigate issues of orthology, heterozygosity and phylogenetic information. We have developed primers and amplification protocols that generate a single PCR product, which, upon direct sequence, shows only very occasional signs of heterozygosity. Now we are focusing our work at two levels: generic relationships within the conifer family Podocarpaceae, and deeper relationships in the seed plants overall. For 18 Podocarpaceae and 2 Araucariaceae, we have amplified the entire XDH gene, and have partial sequence for additional taxa. Within the Podocarpaceae, the alignment includes 980 ungapped sites, 10.6% of which are parsimony informative, and supports one optimal maximum parsimony (MP) tree that is consistent with published trees. For the same representatives, XDH produces a tree with more support using 37% less sequence data than does chloroplast atpB-atpE data. Trying to resolve deeper nodes, sampling from throughout seed plants, we so far have the 5 end of XDH for 26 taxa representing the major extant seed plant lineages. Fifty-one percent of the 735 aligned, ungapped sites are parsimony informative. Two MP trees are recovered, largely consistent with recently published trees, differing only in the relative placement of two genera within one conifer family. In comparison to rbcL, XDH has two times as many parsimony informative sites in 40% less sequence, but to align required 82 gapped positions compared to six for rbcL. Trees based on XDH have an equal number of resolved nodes as rbcL trees with 17 of 18 nodes held in common, the only disagreement occurring within the four included angiosperms. Preliminary analyses of these limited data suggest that XDH may be a promising marker in the gymnosperms.

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1 - Central Washington University, Department of Biological Sciences, 400 E University Way, Ellensburg, WA, 98926-7537, USA
2 - Central Washington University, Biological Sciences, 400 E. University Way, Ellensburg, WA, 98926-7537, U.S.A.
3 - Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsylvania, 15213, USA

seed plant phylogeny
nuclear marker
xanthine dehydrogase.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM
Number: PSP056
Abstract ID:667

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