Systematics Section / ASPT
Les, Donald H. , Crawford, Daniel J. , Tippery, Nicholas P. , Kimball, Rebecca T. , Landolt, Elias .
Duckweeds go nuclear: successful sequencing of nrDNA lends support to the phylogeny of Lemnaceae.
Lemnaceae, an aquatic family of highly reduced monocotyledons, present a formidable challenge to phylogenetic research. Their minute size and negligible phenotypic variation have inspired the analysis of various molecular data sets as a means of elucidating interspecific relationships within the family. Already we have used a combination of anatomical, morphological, biochemical (allozymes, flavonoids) and plastid DNA sequence data (matK, rbcL, rpl16 intron, trnk5’ intron, trnK 3’ intron) to construct a cladogram depicting relationships among all known extant duckweed species that is fully resolved and well-supported (>84% bootstrap support at 89% of nodes). However, all of our data representing nuclear-encoded genes (non-molecular data; allozymes, flavonoids) have been relatively uninformative in comparison to the plastid sequence data. Initially, we attempted to include in our analyses, data from the nuclear-encoded ribosomal repeat (e.g., nrITS), but were unable to amplify and/or sequence data from that region despite numerous attempts and methodological approaches. Here we report on: 1) our successful sequencing of duckweed nuclear DNA (5.8s, 18s, 26s ribosomal genes; ETS, ITS-1, ITS-2 spacers); 2) explanations for failed past sequencing endeavors; and 3) the evaluation of these new sequence data for phylogenetic reconstruction in Lemnaceae. Generally, phylogenetic analysis of the nrDNA sequences corroborates the major clades recovered by our previous combined analysis. However, extensive secondary structure and high levels of divergence in some regions (e.g., ITS) continue to complicate some sequencing efforts and lead to difficulties with sequence alignment.
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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - University of Kansas, Department of Ecology & Evolutionary Biology, Natural History Museum and Biodiversity Research Center, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045-7534, USA
3 - University of Florida, Department of Zoology, P.O. Box 118525, 223 Bartram Hall, Gainesville, Florida, 32611, USA
4 - Geobotanisches Institut ETH, Zürichbergstrasse 38, CH-8044, Zürich, Switzerland
Presentation Type: Oral Paper:Papers for Sections
Location: Stevens 3/Hilton
Date: Monday, July 9th, 2007
Time: 1:30 PM