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A Cytogenetic Study of the White-Throated Sparrow, Zonotrichia albicollis (Gmelin)

H. Bruce Throneycroft
Evolution
Vol. 29, No. 4 (Dec., 1975), pp. 611-621
DOI: 10.2307/2407072
Stable URL: http://www.jstor.org/stable/2407072
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
A Cytogenetic Study of the White-Throated Sparrow, Zonotrichia albicollis (Gmelin)
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Abstract

In a study of nearly 400 white-throated sparrows seven different karyotypes were observed. It is hypothesized that chromosomes 2 and 3 are ancestral and gave rise to chromosomes 2m and 3a by two separate pericentric inversions. In alternate plumage, all birds having chromosome 2m are brightly colored (white-striped); birds lacking this autosome are dull (tanstriped). The presence of chromosome 2m can be predicted in white-striped birds in alternate plumage. White-striped birds of either sex mate with tan-striped birds of the opposite sex. This selective breeding system appears to be based only on the phenotypes determined by the presence or absence of chromosome 2m. Plumage and behavioral polymorphisms based on chromosomal polymorphism promote selective breeding and maintain heterozygosity.

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