Identifying tertiary radiations of Fabaceae in the Greater Antilles: Alternatives to cladistic vicariance analysis

The fossil record shows that the legume family was abundant and taxonomical ly diverse in Early Tertiary tropical deciduous forests of North America. T oday, woody members of this family are almost nonexistent in temperate deci duous forests. This former North American legume diversity now lies in the Tropics, including the Greater Antilles. To show the Antillean refugia, we detail a phylogenetic and biogeographic analysis of two legume groups, the Ormocarpum and Robinia clades, which have either a Tertiary fossil record i n North America or a sister clade with such a fossil record. A combined ana lysis of molecular and nonmolecular data is used for the cladistic vicarian ce approaches, while an exhaustively sampled data set of nrDNA ITS/5.8S seq uences is used for the molecular biogeographic analysis. Results from compo nent, three-area-statements, and Brooks parsimony analysis are equivocal in suggesting an influence of Tertiary history on the distribution of the woo dy genera Pictetia (Ormocarpum clade) and Poitea (Robinia clade), two of th e most speciose endemic legume radiations in the Greater Antilles. Alternat ively, nucleotide diversity, evolutionary rates, and coalescent analyses of molecular phylogenies all suggest a Tertiary diversification of Pictetia a nd Poitea. The results are corroborated by a regression analysis that impli cates both age of island biota and island area in accurately predicting num bers of endemic legume taxa. These findings, combined with the legume fossi l record, suggest that both Pictetia and Poitea stem from Tertiary North Am erican boreotropical groups. J.A. Wolfe's hypothesis that the Greater Antil les harbor boreotropical relicts is supported.