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SnowbirdIntegrative Biology and Evolutionary Diversity in the Junco$
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Ellen D. "Ketterson and Jonathan W. Atwell

Print publication date: 2016

Print ISBN-13: 9780226330778

Published to Chicago Scholarship Online: September 2016

DOI: 10.7208/chicago/9780226330808.001.0001

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The Potential Role of Parapatric and Alloparapatric Divergence in Junco Speciation

The Potential Role of Parapatric and Alloparapatric Divergence in Junco Speciation

(p.199) Chapter Nine The Potential Role of Parapatric and Alloparapatric Divergence in Junco Speciation

Trevor D. Price

Daniel M. Hooper

University of Chicago Press

Speciation may occur as a result of complete divergence in allopatry, or proceed in the face of ongoing migration between populations (parapatric speciation). Gene exchange may also occur intermittently during divergence if populations contract and expand their ranges, occasionally coming in contact (allo-parapatric speciation). We consider these modes of divergence in the establishment of color differences between geographically separated taxa of North American juncos. First, we describe a modern-day junco example of the early stages of differentiation despite gene flow, the result of a resident population becoming established from an over-wintering one in UC San Diego. That population appears to continue to receive immigrants as result of over-wintering birds remaining to breed. Second, climate reconstructions imply multiple range shifts through the Pleistocene, but an important refuge in Alaska. We suggest a novel hypothesis that integrates these observations to explain the low genetic diversity in neutral markers but strong color differences among taxa: individuals from populations of seasonal migrants occasionally interbreed with residents to the south, resulting in directional gene flow from north to south, and an effective population size estimated from neutral markers that is close to that of the northern most populations. Chromosomal inversions, known to be present, may aid differentiation at certain genomic regions.

Keywords:   allo-parapatric, speciation, chromosomal inversions, parapatric speciation, Pleistocene climate

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