A preliminary multigene phylogeny of the diatoms (Bacillariophyta): challenges for future research
Methods – We attempted to obtain a more or less even sampling across the diatom tree. In particular, we increased sampling among the radial and polar centrics and among taxa that morphologically appear to be transitional between polar centrics and araphid pennates. Normal sequencing methods were used. Data were analyzed under maximum likelihood.
Key results – Analysis of SSU and chloroplast data returned many of the same clades and the same general structure of the tree. Combined, the data weakly reject monophyly of the radial centrics. The chloroplast data weakly support monophyly of the polar centrics but SSU and combined data weakly reject polar centric monophyly. There may be an hitherto unrecognized clade of araphid pennates sister to the remaining pennates.
Conclusion – While it is obvious that more genetic data need to be collected, perhaps the greatest obstacle to inferring an accurate, or at least global and robust, diatom phylogeny is the fact that the parts of the diatom tree that appear to be the most intractable to date (relationships among centric groups and between centrics and pennates) are also the most undersampled. This is in part due to major extinctions in the radial and polar centrics. We believe diatomists need to support more effort in both the molecular and morphological studies of these diatoms, and in the search for more information about the first half of the diatom stratigraphic record.
Document Type: Regular Paper
Publication date: 2010-11-01
Plant Ecology and Evolution (a continuation of Belgian Journal of Botany, incorporating Systematics and Geography of Plants) is an international journal devoted to ecology, phylogenetics and systematics of all 'plant' groups in the traditional sense (including algae, cyanobacteria, fungi, myxomycetes), also covering related fields such as comparative and developmental morphology, conservation biology, ecophysiology, evolution, phytogeography, pollen and spores, population biology, and vegetation studies. It is published by the Royal Botanical Society of Belgium and the Botanic Garden Meise and contains original research papers, review articles, checklists, short communications and book reviews.
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