Molecular probes of phylogeny and biogeography in toads of the widespread genus Bufo

Genetic relationships among 25 species of Central and South American Bufoand among representative North, Central, and South American, Asian, andAfrican Bufo were probed, using the quantitative immunological technique ofmicrocomplement fixation (MC'F) which indicated a clear separation ofNorth, Central, and South American lineages of Bufo. The South Americanlineage likely diverged from the Central and North American lineages in theEocene; the latter two lineages diverged later, probably in themid-Oligocene. Some species groups of South American toads, defined on thebasis of traditional morphological studies, are genetically quite similarwithin groups, whereas others are genetically divergent. The amount ofalbumin evolution does not appear to parallel the amount of karyotypic,morphological, ecological, or behavioral evolution documented. Comparisonssuggest that the African lineages separated from the American and Asianlineages in the late Cretaceous, corresponding to the time of the finalseparation of Gondwanaland, the southern supercontinent including themodern continents of South America, Africa, Australia, Antarctica, andIndia. The Asian lineages diverged from the lineage giving rise to all ofthe American species in the early Paleocene.