Rapid phenotypic evolution during incipient speciation in a continental avian radiation
Leonardo Campagna1,*, Pilar Benites1, Stephen C. Lougheed2, Darío A. Lijtmaer1, Adrián S. Di Giacomo3, Muir D. Eaton4 and Pablo L. Tubaro1
Author Affiliations
1División de Ornitología, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Avenida Ángel Gallardo 470, Ciudad de Buenos Aires C1405DJR, Buenos Aires, Argentina
2Department of Biology, Queen's University, 116 Barrie Street, Kingston, Ontario, Canada K7L 3N6
3Laboratorio de Ecología y Comportamiento Animal, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires,Intendente Güiraldes y Avenida Cantilo s/n, Pabellón II Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina
4Biology Department, Drake University, 2507 University, 208 Olin Hall, Des Moines, IA 50311, USA
*Author for correspondence (leocampagna@gmail.com).
Abstract
Adaptive radiations have helped shape how we view animal speciation, particularly classic examples such as Darwin's finches, Hawaiian fruitflies and African Great Lakes cichlids. These ‘island’ radiations are comparatively recent, making them particularly interesting because the mechanisms that caused diversification are still in motion. Here, we identify a new case of a recent bird radiation within a continentally distributed species group; the capuchino seedeaters comprise 11 Sporophila species originally described on the basis of differences in plumage colour and pattern in adult males. We use molecular data together with analyses of male plumage and vocalizations to understand species limits of the group. We find marked phenotypic variation despite lack of mitochondrial DNA monophyly and few differences in other putatively neutral nuclear markers. This finding is consistent with the group having undergone a recent radiation beginning in the Pleistocene, leaving genetic signatures of incomplete lineage sorting, introgressive hybridization and demographic expansions. We argue that this apparent uncoupling between neutral DNA homogeneity and phenotypic diversity is expected for a recent group within the framework of coalescent theory. Finally, we discuss how the ecology of open habitats in South America during the Pleistocene could have helped promote this unique and ongoing radiation.
hybridization, Neotropical birds, phenotypic divergence, recent radiation, speciation
Received October 14, 2011.
Accepted November 11, 2011.
This journal is © 2011 The Royal Society
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