Phylogeny of South American Bufo (Anura: Bufonidae) inferred from combined evidence

Despite the considerable research that has focused on the evolutionary relationships and biogeography of the genus Bufo, an evolutionary synthesis of the entire group has not yet emerged. In the present study, almost 4 kb of DNA sequence data from mitochondrial (12S, tRNA(Val), and 16S) and nuclear (POMC; Rag-1) genes, and 83 characters from morphology were analysed to infer a phylogeny of South American toads. Phylogenies were reconstructed with parsimony and maximum likelihood and Bayesian model-based methods. The results of the analysis of morphological data support the hypothesis that within Bufo, some skull characters (e.g. frontoparietal width), correlated with the amount of cranial ossification, are prone to homoplasy. Unique and unreversed morphological synapomorphies are presented that can be used to diagnose recognized species groups of South American toads. The results of all phylogenetic analyses support the monophyly of most species groups of South American Bufo. In most DNA-only and combined analyses, the South American (minus the B. guttatus and part of the 'B. spinulosus' groups), North American, Central American, and African lineages form generally well-supported clades: ((((((((South America) (North America + Central America)) Eurasia) Africa) Eurasia) South America) West Indies) South America). This result confirms and extends prior studies recovering South American Bufo as polyphyletic. The biogeographical results indicate that: (1) The origin of Bufo predates the fragmentation of Gondwana; (2) Central and North American species compose the sister group to a large, 'derived' clade of South American Bufo; and (3) Eurasian species form the sister group to the New World clade. (c) 2006 The Linnean Society of London.