Mediterranean regions are some of the most unique and biologically fascinating areas on the face of the Earth. Corresponding largely to the Cape region of South Africa, central Chile, southwest and southern Australia, California and the borders of the Mediterranean Sea, these five regions exhibit remarkable similarities in climate, topography and flora and fauna. How similarities in the flora and fauna arose, however, has been a question of considerable interest and debate. The discovery of the underlying phylogenetic relationships of organisms inhabiting these areas can lead to an increased understanding of their evolution and diversification. In this study, we investigate the biogeography of two groups of morphologically similar plant taxa that occupy two different mediterranean regions: western North America and mediterranean Eurasia. Taxa of the two groups were sequenced for the ITS1, 5.8S and ITS2 regions of nuclear ribosomal DNA and their phylogenetic relationships were estimated using parsimony. We are also investigating the phylogenetic utility of the trnL region of cpDNA. Evidence based on ITS, however, suggests that the largest taxon, Lotus, is not monophyletic, but is composed of separate western North American and Eurasian clades. This suggests that the morphological similarities observed between Old and New World Lotus are either the result of convergence or are symplesiomorphic. Mapping of the character "region" onto the phylogeny suggests a complex biogeographic scenario involving multiple dispersals from Eurasia to western North America, followed by back dispersal to Eurasia. This dispersal pattern suggests a series of multiple, intercontinental dispersals that involve not only Lotus, but the Eurasian taxon Coronilla as well. These results provide insight into the evolution of morphological similarities in tribe Loteae, and yield a preliminary framework for assessing the biogeography of other temperate legume taxa occupying disjunct mediterranean regions

Key words: Biogeography, ITS, Loteae, phylogeny