RT Journal Article SR Electronic T1 Origin and cross-century dynamics of an avian hybrid zone JF bioRxiv FD Cold Spring Harbor Laboratory SP 012856 DO 10.1101/012856 A1 Andrea Morales-Rozo A1 Elkin A. Tenorio A1 Matthew D. Carling A1 Carlos Daniel Cadena YR 2014 UL http://biorxiv.org/content/early/2014/12/16/012856.abstract AB Background Characterizations of the dynamics of hybrid zones in space and time can give insights about traits and processes important in population divergence and speciation. We characterized a hybrid zone between tanagers in the genus Ramphocelus (Aves, Thraupidae) located in southwestern Colombia. We tested whether this hybrid zone originated as a result of secondary contact or of primary differentiation, and described its dynamics across time using spatial analyses of molecular, morphological, and coloration data in combination with paleodistribution modeling.Results Models of potential historical distributions based on climatic data and genetic signatures of demographic expansion suggested that the hybrid zone originated following secondary contact between populations that expanded their ranges out of isolated areas in the Quaternary. Concordant patterns of variation in phenotypic characters across the hybrid zone and its narrow extent are suggestive of a tension zone, maintained by a balance between dispersal and selection against hybrids. Estimates of phenotypic cline parameters obtained using specimens collected over nearly a century revealed that, in recent decades, the zone has moved to the east and to higher elevations, and has become narrower. Genetic variation was not clearly structured along the hybrid zone, but comparisons between historical and contemporary specimens suggested that temporal changes in its genetic makeup may also have occurred.Conclusions Our data suggest that the hybrid zone resulted from secondary contact between populations. The observed changes in the hybrid zone may be a result of sexual selection, asymmetric gene flow, or environmental change.