MOLECULAR SYSTEMATICS AND BIOGEOGRAPHY OF ANTILLEAN THRASHERS, TREMBLERS, AND MOCKINGBIRDS (AVES: MIMIDAE)

Abstract

We constructed phylogenetic hypotheses for Greater and Lesser Antillean Mimidae, including five endemic species of tremblers and thrashers that represent the best plausible example of an avian radiation within the Lesser Antilles. Phylogenetic relationships were inferred from analysis of 3,491 base pairs (bp) of mitochondrial DNA (mtDNA) and roughly 780 bp of the nuclear-encoded myoglobin gene. We used a subset of mtDNA gene sequences and pcrRFLP analysis to evaluate the phylogeographic relationships among individuals representing island populations of the Brown and Gray tremblers (Cinclocerthia ruficauda and C. gutturalis), Pearly-eyed Thrasher (Margarops fuscatus), Scaly-breasted Thrasher (Margarops fuscus), and Antillean and continental populations of the Tropical (Mimus gilvus) and Northern mockingbirds (Mimus polyglottos). Phylogeographic analysis distinguished three strongly differentiated mtDNA clades among tremblers, as well as distinct southern (St. Lucia and Martinique) and northern (Dominica to Montserrat) mtDNA lineages of the Scaly-breasted Thrasher. Minor geographic subdivision was also observed between continental and Antillean populations of the Tropical Mockingbird. Phylogenetic analyses of species-level Mimidae relationships that are based on mtDNA and nuclear sequences provide strong support for the monophyly and Antillean origin of a clade that consists of the tremblers, Pearly-eyed Thrasher, and Scaly-breasted Thrasher, but reject the monophyly of the genus Margarops. Phylogenetic analysis cannot confirm the monophyly of all endemic Antillean mimids because of the apparently contemporaneous diversification of the Antillean White-breasted Thrasher (Ramphocinclus brachyurus) with the continental Gray Catbird (Dumetella carolinensis) and Black Catbird (Melanoptila glabrirostris). However, an insertion and a deletion in the myoglobin intron 2 sequence support grouping the West Indian thrashers and tremblers, from which we infer that the endemic Lesser Antillean mimids are an indigenous radiation. Assuming a constant mtDNA clock for the Mimidae, the splitting of the Northern and Tropical mockingbird lineages is roughly contemporaneous with the separation of the three trembler clades, as well as the two Scaly-breasted Thrasher clades. Application of a mitochondrial DNA clock ticking at 2% sequence divergence per million years (Ma), suggests that the history of the endemic thrasher and trembler lineage in the West Indies extends back about 4 Ma, and the three distinct clades of tremblers split about 2 Ma ago.