A cladistic analysis of the new world species of Lotus L. (Fabaceae, Loteae)

The genus Lotus L. is a monophyletic group diagnosed by the possession of a standard claw with thickened infolded margin, stamens diadelphous, and the style hardened from the base. It comprises approximately 200 species distr ibuted throughout the world. A cladistic analysis of the New World species was performed using 39 morphological and anatomical characters (29 from see d morphology and anatomy, 1 from plant habit, 1 from leaf morphology, 6 fro m flower morphology, and 2 from fruit morphology). Dorycnium, Edentolotus, Krokeria, and Pedrosia, of the Old World, and 28 species of the New World w ere considered terminal taxa. Tetragonolobus Scop. was chosen to root the c ladograms and Dorycnium Mill. to reroot them. With Tetragonolobus the analy sis yielded 15 equally parsimonious trees, each with a length of 74 steps, a consistency index of 0.62, and a retention index of 0.89. The 15 initial trees and the strict consensus tree defined 12 monophyletic groups. All ter minal taxa form a monophyletic group diagnosed by the presence of a radicul ar lobe discernible to conspicuous (character 10); rim aril thick (characte r 13); stipules absent (character 31); and style simple and nondilated (cha racter 36). The New World species form a monophyletic group on the basis of the seed relationship of length to width in hilar view 1.5:1 to 2:1 (chara cter 5); micropyle linear-deltoid to bifurcate (character 19); and keel ero strate (character 33). Identical monophyletic groups were obtained when Dor ycnium was used as root. These results are discussed in the context of data on cytology and morphology. (C) 2000 The Willi Hennig Society.