Phylogenetic and Biogeographic Aspects of Sophora Sect. Edwardsia (Papilionaceae)

Sophora comprises 45-50 species of worldwide distribution, but no general proposal as to the evolution of this group has been put forth. We used cladistic relationships of the quinolizidine alkaloids (matrine, sparteine, methylcytisine, anagyrine, and sophoranol) with morphological and palynological characters to suggest a hypothesis of evolutionary and biogeographic relationships. The mainland Chilean species of Sophora appear to have been derived from' ancestors phylogenetically near the extant Argentinean species S. linearifolia and S. rhynchocarpa and the psammophyte S. tomentosa, growing at tropical coastal sites around the world. The Boreotropic hypothesis of Lavin and Luckow is incorporated in our model as the most parsimonious explanation of the evolution of the species of Edwardsia. Sophora is a taxonomic group that meets the following criteria: a center of diversity in North America, an early Tertiary record in North America, and a pantropical distribution. Styphnolobium and Sophora (including Calia) are representatives of Sophora s.l. in the United States, suggesting a migration of the latter from the Northern Hemisphere to South America. Consistent with the Boreotropic hypothesis, a primary diversification center in South America and subsequent migration to the Indian Ocean and New Zealand, the Juan Fernandez Archipelago, Easter Island, and possibly the Hawaiian Islands is the simplest explanation for the evolution of the Edwardsia species. 1 This study was made possible by the financial support of the Fondo Nacional de Ciencia y Tecnologia (FONDECYT) Chile, Grant No. 1980967 to G.M. and NIH Grant 2 UOI TW 00316-06 to B. Timmermann. Manuscript accepted I August 1999. 2Ecology Department, Pontificia Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile. 3Faculty of Sciences, Universidad de Chile, P.O. Box 653, Santiago, Chile. The genus Sophora is a taxonomic group of pantropical distribution but with its center of diversity and an early Tertiary record in North America. Sousa and Rudd (1993) distinguished Sophora as perennials, shrubs, or trees without bracteoles and with a dehiscent legume, and Calia and Styphnolobium as trees with flowers with bracteoles and nondehiscent fruit. Styphnolobium differs from Calia in having leaves with stipels and legume with fleshy mesoand endocarp. Styphnolobium affine (Torr. and A. Gray) Walp grows well in deciduous forests and grasslands. Styphnolobium japonicum is a deciduous tree endeniic to' China. Sophora macrocarpa is a characteristic endemic shrub from Chile that grows in open places or under the forest canopy. Sophora prostrata, a divaricate suckering shrub from New Zealand, grows well in grassland and rocky places. In contrast, the majority of the species of Edwardsia prefer lowland or lower mon159 VALID SPECIES OF Sophora following revisions of Allan (1961), Yakovlev (1967), Green (1970), Godley (1979), Isely (1981), Tsoong and Ma (1981), and Heenan (1998) are listed in Table 1. Although Tsoong and Ma (1981) merged Calia and Styphnolobium, it is better to consider them as two distinctive taxa taking into account first the cytogenetic differences, chromosome number, and karyotypes, and second the distinctive germination mode of Styphnolobium and Sophora sect. Calia (Palomino et al. 1993).