Error, Bias, and Long-Branch Attraction in Data for Two Chloroplast Photosystem Genes in Seed Plants
Sanderson, M.J., Wojciechowski, M.F., Hu, J.M., Sher Khan, T., & Brady, S.G. (2000) Error, Bias, and Long-Branch Attraction in Data for Two Chloroplast Photosystem Genes in Seed Plants. Molecular Biology and Evolution, 17(5), pp. 782-797.
Sequences of two chloroplast photosystem genes, psaA and psbB, together comprising about 3,500 bp, were obtained
for all five major groups of extant seed plants and several outgroups among other vascular plants. Strongly supported,
but significantly conflicting, phylogenetic signals were obtained in parsimony analyses from partitions of the data
into first and second codon positions versus third positions. In the former, both genes agreed on a monophyletic
gymnosperms, with Gnetales closely related to certain conifers. In the latter, Gnetales are inferred to be the sister
group of all other seed plants, with gymnosperms paraphyletic. None of the data supported the modern ‘‘anthophyte
hypothesis,’’ which places Gnetales as the sister group of flowering plants. A series of simulation studies were
undertaken to examine the error rate for parsimony inference. Three kinds of errors were examined: random error,
systematic bias (both properties of finite data sets), and statistical inconsistency owing to long-branch attraction (an
asymptotic property). Parsimony reconstructions were extremely biased for third-position data for psbB. Regardless
of the true underlying tree, a tree in which Gnetales are sister to all other seed plants was likely to be reconstructed
for these data. None of the combinations of genes or partitions permits the anthophyte tree to be reconstructed with
high probability. Simulations of progressively larger data sets indicate the existence of long-branch attraction (statistical
inconsistency) for third-position psbB data if either the anthophyte tree or the gymnosperm tree is correct.
This is also true for the anthophyte tree using either psaA third positions or psbB first and second positions. A
factor contributing to bias and inconsistency is extremely short branches at the base of the seed plant radiation,
coupled with extremely high rates in Gnetales and nonseed plant outgroups.
M. J. Sanderson,* M. F. Wojciechowski,*† J.-M. Hu,* T. Sher Khan,* and S. G. Brady
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|Item Type:||Journal Article|
|Additional Information:||Fulltext is freely accessible on Publisher's website. See Official URL.|
|Keywords:||statistical consistency, maximum likelihood, parsimony.|
|Subjects:||Australian and New Zealand Standard Research Classification > BIOLOGICAL SCIENCES (060000) > EVOLUTIONARY BIOLOGY (060300)|
|Divisions:||Past > Schools > Biogeoscience|
Past > QUT Faculties & Divisions > Faculty of Science and Technology
|Copyright Owner:||Society for Molecular Biology and Evolution|
|Deposited On:||06 Jul 2009 13:04|
|Last Modified:||11 Aug 2011 04:22|
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