Abstract
BackgroundThe Neotropics are exceptionally diverse, containing roughly one third of all extant bird species on Earth. This remarkable species richness is thought to be a consequence of processes associated with both Andean orogenesis throughout the Tertiary, and climatic fluctuations during the Quaternary. Phylogeographic studies allow insights into how such events might have influenced evolutionary trajectories of species and ultimately contribute to a better understanding of speciation. Studies on continentally distributed species are of particular interest because different populations of such taxa may show genetic signatures of events that impacted the continent-wide biota. Here we evaluate the genealogical history of one of the world’s most broadly-distributed and polytypic passerines, the rufous-collared sparrow (Zonotrichia capensis).ResultsWe obtained control region DNA sequences from 92 Zonotrichia capensis individuals sampled across the species’ range (Central and South America). Six additional molecular markers, both nuclear and mitochondrial, were sequenced for a subset of individuals with divergent control region haplotypes. Median-joining network analysis, and Bayesian and maximum parsimony phylogenetic analyses all recovered three lineages: one spanning Middle America, the Dominican Republic, and north-western South America; one encompassing the Dominican Republic, Roraima (Venezuela) and La Paz (Bolivia) south to Tierra del Fuego, Argentina; and a third, including eastern Argentina and Brazil. Phylogenetic analyses suggest that the Middle American/north-western South American clade is sister to the remaining two. Bayesian and maximum likelihood coalescent simulations used to study lineage demographic history, diversification times, migration rates and population expansion together suggested that diversification of the three lineages occurred rapidly during the Pleistocene, with negligible gene flow, leaving genetic signatures of population expansions.ConclusionsThe Pleistocene history of the rufous-collared sparrow involved extensive range expansion from a probable Central American origin. Its remarkable morphological and behavioral diversity probably represents recent responses to local conditions overlying deeper patterns of lineage diversity, which are themselves produced by isolation and the history of colonization of South America.
Highlights
The Neotropics are exceptionally diverse, containing roughly one third of all extant bird species on Earth
Our analyses revealed three main lineages within Z. capensis that diversified without gene flow during the Pleistocene, expanding to colonize South America from a probable Central American origin
Note that two localities show admixture of two lineages: haplotypes from A and B were found in the Dominican Republic and haplotypes from B and C were found in Corrientes, Argentina
Summary
The Neotropics are exceptionally diverse, containing roughly one third of all extant bird species on Earth. While most of South America’s continental biota has not been as deeply influenced by glaciations (e.g., [4,5]; but see [6,7]), over the last several million years, the continent has experienced marked topographic, climatic and vegetational changes, even at low and mid latitudes (e.g., [8,9,10]), much of this associated with orogenesis at the continent’s western margins (e.g., [11,12,13]) The interaction of these factors has been proposed to underlie much of the hyperdiversity evident in the Neotropics (e.g., [14,15,16,17]). The rufous-collared sparrow, Zonotrichia capensis, is an excellent species for examining the influence of a dynamic continental history on intraspecific evolutionary patterns It is one of the most wide-ranging New World birds, distributed from Chiapas, Mexico (10°N) to Tierra del Fuego, Argentina (55°S). Contrary to Chapman’s scenario [18], such a Central or South American origin would imply an expansion and diversification towards the North, generating the clade found currently in North America, and the expansion of the Z. capensis lineage within Central and South America
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