Historical biogeography of the new world solitaires (Myadestes spp)

Matthew J Miller, Eldredge Bermingham, Robert E Ricklefs, BMC Evolutionary Biology 124 :868-885 (2007).
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Solitaires (Myadestes spp.) are montane-forest birds that are widely distributed throughout the New World, ranging from Alaska to northern Bolivia and including both Hawaii and the West Indies. To understand the origins of this impressive distribution, we used five mitochondrial gene sequences to reconstruct the historical biogeography of the genus. The resulting phylogeny indicates a rapid initial spread of the genus to occupy most of its contemporary continental range at least as far south as lower Mesoamerica, plus Hawaii and the Greater Antilles. The North American M. townsendi appears to be the sister taxon of the rest of Myadestes. Myadestes obscurus of Hawaii is more closely allied to Mesoamerican lineages than to M. townsendi. The strongly supported sister relationship of the two West Indian taxa, M. elisabeth and M. genibarbis, indicates a single colonization of the West Indies. A more recent node links the Andean M. ralloides to the Mesoamerican M. melanops and M. coloratus. A standard molecular clock calibration of 2% sequence divergence per million years for avian mitochondrial DNA suggests that the initial diversification of Myadestes occurred near the end of the Miocene (between 5 and 7.5 mya). Cooler temperatures and lower sea levels at that time would have increased the extent of montane forests and reduced overwater dispersal distances, possibly favoring range expansion and colonization of the West Indies. The split between South American and southern Mesoamerican lineages dates to ∼3 mya, which suggests that Myadestes expanded its range to South America soon after the Pliocene rise of the Isthmus of Panama. Despite the demonstrated capacity of Myadestes for long-distance dispersal, several species of Myadestes are highly differentiated geographically. Phylogeographic structure was greatest in the West Indian M. genibarbis, which occurs on several islands in the Greater Antilles and Lesser Antilles, and in the Andean M. ralloides. The phylogeographic differentiation within M. ralloides was not anticipated by previous taxonomic treatments and provides a further example of the importance of the Andes in the diversification of Neotropical birds. Overall, the historical biogeography of Myadestes suggests that range expansion and long-distance dispersal are transient population phases followed by persistent phases of population differentiation and limited dispersal.