Revision and probable evolution of the Myiarchus flycatchers of the West Indies. Bulletin of the AMNH ; v. 136, article 6
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Abstract
"The extent of morphological and vocal divergence among West Indian populations of Myiarchus is documented, and a key to the identification of these flycatchers is included. Of the 12 recognizable taxa, seven species (all endemic) are admitted. No new forms are recognized, but substantial changes in specific limits are recommended, based principally on the response of territorial males to the playback of vocal repertoires: four monotypic species, including two on Jamaica (M. validus and M. barbirostris), one on Puerto Rico (M. antillarum), and one in the southern Lesser Antilles (M. nugator); three polytypic species, including one on Cuba, Grand Cayman, and the Bahamas (M. sagrae), one on Jamaica and Hispaniola (M. stolidus), and one in the northern Lesser Antilles (M. oberi). An attempt is made to reconstruct the evolution of these species as newly constituted, and to determine their relative ages, origins, and paths of entry into the West Indian region. It is postulated that Myiarchus entered the West Indies by four primary invasions: three by way of Jamaica, from the Honduran-Nicaraguan bulge, and one via Grenada from Venezuela. The oldest invasion, perhaps by an obscure species in the late Tertiary avifauna of Middle America, led to the development of M. stolidus on Jamaica and Hispaniola. Subsequent range expansions from Hispaniola led to the evolution of M. sagrae and M. antillarum in the Greater Antilles and, more recently, to the polytypic M. oberi in the Lesser Antilles. In order not to obscure the relationships between these species, which are thought to have been derived from stolidus of Jamaica, it is recommended that they be considered a superspecies. After the submergence of the Greater Antillean land masses in the early Pleistocene, a second invasion of Jamaica by a Middle American Myiarchus, now obscure, resulted in the endemic M. validus. A third invasion of Jamaica, probably in the mid or late Pleistocene, by a representative of M. tuberculifer of Middle America, produced another endemic, M. barbirostris. The fourth invasion, no earlier than late Pleistocene, involved the range extension of M. tyrannulus from Venezuela into Grenada. With subsequent isolation this population evolved into M. nugator. Its expansion north of St. Vincent was blocked by a water barrier and competition with a congener already established on St. Lucia. This study of insular populations supports evidence, gained previously from continental species of this genus, that suggests a relative plasticity of morphology in contrast to the conservativeness of certain vocal characters. It has also demonstrated the efficacy of using the behavioral responses of territorial males to experimental playback of vocal repertoires for determining the specific limits of allopatric populations of Myiarchus"--P. 368.
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Includes bibliographical references (p. 368-370).