The geological association of the Greater Antilles with North and South America in the late Cretaceous led to the hypothesis that the present Antillean biota reflects those ancient land connections. Molecular data from diverse West Indian amphibians and reptiles and their mainland relatives support a more recent derivation of the Antillean vertebrate fauna by overwater dispersal. The catastrophic bolide impact in the Caribbean region at the close of the Cretaceous provides a proximate cause for the absence of an ancient West Indian biota.

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Antisera to serum albumins from five West Indian species of the frog genus Eleutheroductylus were prepared, and the reciprocal immunological distances (IDs) obtained were used to provide a time frame for the evolution of this group in the West Indies. One‐way IDS were obtained to 25 additional species within the genus, with emphasis on those from the West Indies. These immunological data support both a recent classification of Eleutheroductylus based on an analysis of slow‐evolving allozyme loci, and the monophyly of the 17 native Jamaican species as indicated by a more comprehensive electrophoretic study. This is in contrast to the results of morphological studies supporting multiple invasions of Jamaica by Eleutherodactylus. Within the subgenus Euhyas, IDS ranged from6–27 between Jamaican species, whereas between species on different islands the range was29–67. The subgenus Syrrhophus in southern North America was found to be the sister group to the subgenus Euhyus, a western Caribbean clade. Pelorius, a subgenus restricted to Hispaniola, was found to be the sister group of the subgenus Eleutheroductylus in the West Indies. The largest IDs obtained for West Indian species were those between the two major groups, the subgenera Eleutheroductylus and Euhyas. The albumin immunological clock for Eleutheroductylus was calibrated with three events in the geologic history of the Caribbean: the breakup of the proto‐Antilles (65‐75 million years before present [mybp]), the emergence of Jamaica (20‐30 mybp), and the uplift of the Blue Mountains in Jamaica (5‐10 mybp). Immunological distances corresponding to those events yield a calibration of 1 ID=0.60 million years (my), the same as that previously obtained for other groups of amphibians and thus supports the use of albumin immunological distance as a molecular chronometer in the genus Eleutherodactylus

Abstract-The realization that the present day positions of continents and island arcs are a result of continental drift led to the proposal that the extant West Indian fauna reflect an ancient (Cretaceous) land connection between the proto-Antilles and North and South America. Movements of the Antillean islands throughout the Cenozoic are hypothesized to have further fragmented the fauna present on the protoAntilles when it separated from the mainland 70-80 million years ago. This proposed vicariant origin of the West Indian fauna challenged the previous theory that some or most of the fauna arrived in the Antilles by overwater dispersal from mainland sources. The virtual absence of appropriate fossils in the West Indies has hampered testing these alternative hypotheses for the origin of the present day West Indian fauna.We present evidence from two types of molecular data, one providing indirect estimates of amino acid sequence divergence for the protein serum albumin, and the other direct DNA sequence information from a mitochondrial ribosomal RNA gene. Our new data provide insights into the origin and relationships of two enigmatic lizard genera, Chamae/eo/is and Chamae/inorops, and suggest they are recent derivatives within' the genus Ana/is. These data, along with molecular data presented elsewhere, strongly implicate an origin by overwater dispersal for most of the Antillean vertebrate fauna.