1. School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236, USA
2. Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK

Correspondence to: Pamela S. Soltis¹ Correspondence and requests for material should be addressed to P.S.S. (e-mail: Email: psoltis@wsu.edu).

Comparative biology requires a firm phylogenetic foundation to uncover and understand patterns of diversification and evaluate hypotheses of the processes responsible for these patterns. In the angiosperms, studies of diversification in floral form^{1, 2}, stamen organization³, reproductive biology⁴, photosynthetic pathway⁵, nitrogen-fixing symbioses⁶ and life histories⁷ have relied on either explicit or implied phylogenetic trees. Furthermore, to understand the evolution of specific genes and gene families, evaluate the extent of conservation of plant genomes and make proper sense of the huge volume of molecular genetic data available for model organisms⁸ such as Arabidopsis, Antirrhinum, maize, rice and wheat, a phylogenetic perspective is necessary. Here we report the results of parsimony analyses of DNA sequences of the plastid genes rbcL and atpB and the nuclear 18S rDNA for 560 species of angiosperms and seven non-flowering seed plants and show a well-resolved and well-supported phylogenetic tree for the angiosperms for use in comparative biology.