Cover Illustration: The classic schematic plant of J. von Sachs (Physiology of Plants. 1887. Clarendon Press, Oxford, UK) is superimposed onto repeats of the phytochrome DNA sequence to represent the plant body as an “emergent property” of the underlying genome, circumscribed by its sequence data. Just as the plant body is built as repeats of a leaf-internode unit, DNA sequence data has morphological structure. For any sequence that encodes mRNA, the basic unit is the triplet codon-in 61 different amino-acid specifications. In a morphological approach to the DNA data sets used in phylogenetic reconstructions, Christianson found that the preferred use of certain triplets was found to lead to coincidence of triplets within taxa, to exaggerated divergence in sequence between taxa, and, consequently, to problems for algorithms that treat each base as an independent character. See: Codon usage patterns distort phylogenies from or of DNA sequences, pp. 1221-1233 in this issue. Cover credit: Steve Marstall, after an idea by Michael L. Christianson.
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Copyright © 2005 by the Botanical Society of America, Inc.
