Evolution Of C-Values Across Land Plants (Embryophyta)

IJ Leitch1, D Soltis3, P Soltis2, and MD Bennett1

1Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK
2Department of Botany and the Genetics Institute, University of Florida, Gainesville, FL 32611, USA
3Florida Museum of Natural History and the Genetics Institute, University of Florida, Gainesville, FL 32611, USA

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Abstract


    In land plants (embryophytes), DNA C-values range over 1000-fold from c. 0.1 pg to 127.4 pg. To understand the evolutionary significance of this huge variation, it is essential to evaluate these data in a phylogenetic context. Recent increases in C-value data, e.g. the Plant DNA C-values Database (release 2.0, Jan. 2003; http://www.rbgkew.org.uk/cval/homepage.html), together with improved consensus of the phylogeny of land plants make such an analysis timely. Consequently, we reconstructed the evolution of genome size using data for 4538 species representing 4119 angiosperms, 181 gymnosperms, 67 lycophytes and ferns and 171 mosses, liverworts and hornworts and a well-supported phylogenetic tree. Using the definitions of very small (<1.4 pg), small (<3.5 pg), large (>14 pg) and very large (>35 pg) to characterise C-values (as originally outlined in Leitch et al.1), our analyses revealed that the ancestral C-value of all land plants was very small. These analyses further provided evidence for several independent increases and decreases in genome size2. Thus in agreement with several focused studies within angiosperm families and genera showing that C-values may both increase and decrease, it is apparent that this dynamic pattern of genome size evolution is repeated on a broad scale across land plants.

    1. Leitch IJ, Chase M, Bennett MD. (1998) Annals of Botany 82: 85-94
    2. Soltis D, Soltis P, Bennett MD, Leitch IJ. American Journal of Botany (in press)