A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus)

T. Hatfield, N.H. Barton, J. Searle, Evolution; International Journal of Organic Evolution 46 (1992) 1129–1145.

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Abstract
The common shrew (Sorex araneus) is subdivided into several karyotypic races in Britain. Two of these races meet near Oxford to form the "Oxford-Hermitage" hybrid zone. We present a model which describes this system as a "tension zone," i.e., a set of clines maintained by a balance between dispersal and selection against chromosomal heterozygotes. The Oxford and Hermitage races differ by Robertsonian fusions with monobrachial homology (kq, no versus ko), and so F1 hybrids between them would have low fertility. However, the acrocentric karyotype is found at high frequency within the hybrid zone, so that complex Robertsonian heterozygotes (kq no/q ko n) are replaced by more fertile combinations, such as (kq no/k q n o). This suggests that the hybrid zone has been modified so as to increase hybrid fitness. Mathematical analysis and simulation show that, if selection against complex heterozygotes is sufficiently strong relative to selection against simple heterozygotes, acrocentrics increase, and displace the clines for kq and no from the cline for ko. Superimposed on this separation is a tendency for the hybrid zone to move m favor of the Oxford (kq no) race. We compare the model with estimates of linkage disequilibrium and cline shape made from field data.
Publishing Year
Date Published
1992-08-01
Journal Title
Evolution; International Journal of Organic Evolution
Volume
46
Issue
4
Page
1129 - 1145
IST-REx-ID

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Hatfield T, Barton NH, Searle J. A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus). Evolution; International Journal of Organic Evolution. 1992;46(4):1129-1145.
Hatfield, T., Barton, N. H., & Searle, J. (1992). A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus). Evolution; International Journal of Organic Evolution, 46(4), 1129–1145.
Hatfield, Todd, Nicholas H Barton, and Jeremy Searle. “A Model of a Hybrid Zone between Two Chromosomal Races of the Common Shrew (Sorex Araneus).” Evolution; International Journal of Organic Evolution 46, no. 4 (1992): 1129–45.
T. Hatfield, N. H. Barton, and J. Searle, “A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus),” Evolution; International Journal of Organic Evolution, vol. 46, no. 4, pp. 1129–1145, 1992.
Hatfield T, Barton NH, Searle J. 1992. A model of a hybrid zone between two chromosomal races of the common shrew (Sorex araneus). Evolution; International Journal of Organic Evolution. 46(4), 1129–1145.
Hatfield, Todd, et al. “A Model of a Hybrid Zone between Two Chromosomal Races of the Common Shrew (Sorex Araneus).” Evolution; International Journal of Organic Evolution, vol. 46, no. 4, Wiley-Blackwell, 1992, pp. 1129–45.

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