Pleistocene glacial cycles have often been hypothesized to provide vicariant mechanisms leading to allopatric speciation in a wide range of southern South American (Fuegian and Patagonian) avian taxa. Few of those biogeographic hypotheses, however, have been rigorously tested using phylogenetic analysis. We examined sequence variation in three mitochondrial gene fragments (cytochrome b, ND2, and ND3) to construct a molecular phylogeny for the South American genus Geositta (Furnariidae) and to test the interrelated hypotheses that Geositta cunicularia and G. antarctica are sister species that originated from a common ancestor while isolated in glacial refugia during Pleistocene glacial events in Fuego-Patagonia. Sequence data were obtained for all 10 currently recognized species of Geositta as well as Geobates poecilopterus and two outgroup taxa (Upucerthia ruficauda and Aphrastura spinicauda). We found levels of sequence divergence among Geositta species to be high, ranging from 7.4% to 16.3%. Our phylogenetic reconstructions clearly indicate relationships among Geositta species that differ considerably from those of traditional Geositta phylogeny. These data also strongly suggest that Geositta, as currently defined, is paraphyletic, with Geobates being embedded within Geositta. Our data do not support the hypothesized sister relationship between G. antarctica and G. cunicularia. Instead, they suggest that Geositta consists of two distinct clades, with antarctica and cunicularia falling into different clades. The high levels of sequence divergence among Geositta species, lack of a sister relationship between cunicularia and antarctica, and placement of Fuego-Patagonian antarctica into a clade consisting of two high-Andean (saxicolina and isabellina) and one coastal-west-slope (maritima) species demonstrate that the evolutionary history of Geositta is much older and far more complex than a simple model of allopatric speciation in glacial refugia would suggest.
Filogenia Molecular del Género Geositta (Furnariidae) e Implicaciones Biogeográficas para la Especiación de la Aves en Tierra del Fuego y Patagonia