Reconstructing the Phylogeny of Legumes (leguminosae): an Early 21st Century Perspective

Elucidating the phylogenetic relationships of the legumes is essential for understanding the evolutionary history of events that underlie the origin and diversification of this family of ecologically and economically important flowering plants. In the ten years since the Third International Legume Conference (1992), the study of legume phylogeny using molecular data has advanced from a few tentative inferences based on relatively few, small datasets into an era of large, increasingly multiple gene analyses that provide greater resolution and confidence, as well as a few surprises. Reconstructing the phylogeny of the Leguminosae and its close relatives will further advance our knowledge of legume biology and facilitate comparative studies of plant structure and development, plant-animal interactions, plant-microbial symbiosis, and genome structure and dynamics. Phylogenetic relationships of Leguminosae — what has been accomplished since ILC-3? The Leguminosae (Fabaceae), with approximately 720 genera and more than 18,000 species worldwide (Lewis et al., in press) is the third largest family of flowering plants (Mabberley, 1997). Although greater in terms of the diversity of forms and number of habitats in which they reside, the family is second only perhaps to Poaceae (the grasses) in its agricultural and economic importance, and includes species used for foods, oils, fibre, fuel, timber, medicinals, numerous chemicals, cultivated horticultural varieties, and soil enrichment. Ecologically, the family is important in a diversity of ecosystems, especially members of the subfamily Papilionoideae which are present and often dominant, in nearly every vegetation type on Earth, from tropical rain forests to deserts and alpine tundra, and play a vital role in global biogeochemistry; nearly all species root-nodulate with symbiotic bacteria to fix atmospheric nitrogen (Sprent and McKey, 1994; Sprent, 2001). Given the paramount ecological and economic importance of legumes, the evolution and systematics of the family are topics of long-standing interest to a large community of academic, agricultural and government researchers representing a broad spectrum of scientific disciplines. The years since the Third International Legume Conference (ILC-3; Kew, 1992) have been especially productive ones for all areas of legume biology, from paleobotanical, anatomical, and phylogenetic studies, to studies dealing with crop diversity and nitrogen biology. The set of volumes in the “Advances in Legume Systematics” series published since the conference attest to this ongoing and ever increasing interest 5 Wojciechowski, M.F. (2003). Reconstructing the phylogeny of legumes (Leguminosae): an early 21st century perspective In: B.B. Klitgaard and A. Bruneau (editors). Advances in Legume Systematics, part 10, Higher Level Systematics, pp. 5–35. Royal Botanic Gardens, Kew. * author for correspondence: [email protected] in legume systematics and comparative biology (Herendeen and Dilcher, 1992; Ferguson and Tucker, 1994; Sprent and McKey, 1994; Crisp and Doyle, 1995; Pickersgill and Lock, 1996; Herendeen and Bruneau, 2000). Furthermore, a cursory survey of the primary literature (Current