Abstract
Selection against chromosomal heterozygotes causing a limitation of gene flow between parental forms could promote genetic changes leading to speciation. Hence, the analysis of the fertility of hybrids and the pure form individuals from chromosomal hybrid zones offers a possibility to study the role of chromosomes in the speciation process. In this study, meiosis and spermatogenesis of homozygotes, simple Rb heterozygotes and complex heterozygotes of the male common shrews from the Dn/Bi hybrid zone were analyzed. It was found out that the Dn/Bi hybrids were not sterile, but they suffered from substantial germ cell death and were characterized by high level of chromosome non-disjunction at anaphase I. However, we suppose that speciation is not possible in the studied area, because effects of selection acting against hybrids are obliterated by inflow of pure race individuals and genetic drift.
Zusammenfassung
Selektion gegen chromosomale Heterozygote, die eine Einschränkung des Genflusses zwischen den Elternformen bewirkt, kann genetische Veränderungen fördern, die schließlich Artbildung zur Folge haben. Fruchtbarkeitsanalysen bei derartigen Hybriden und den jeweiligen reinen Formen aus chromosomalen Hybridzonen ermöglichen es, die Rolle der Chromosomen im Artbildungsprozeß zu untersuchen. In der vorliegenden Arbeit wurden die Meiose und die Spermatogenese von Homozygoten, einfachen Rb-Heterozygoten und komplexen Heterozygoten aus einer Dn/Bi-Hybridzone männlicher Waldspitzmäuse analysiert. Die Dn/Bi-Hybriden waren nicht steril, wiesen aber einen beträchtlichen Anteil an toten Keimzellen sowie einen hohen Grad an chromosomaler Non-Disjunktion in der Anaphase I auf. Wir nehmen jedoch an, dass im Untersuchungsgebiet keine Artbildung möglich ist, da die Effekte der Selektion gegen Hybride durch das Einströmen von Individuen aus den reinen Rassen und durch genetische Drift herabgesetzt sind.
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Jadwiszczak, K.A., Banaszek, A. Fertility in the male common shrews, Sorex araneus, from the extremely narrow hybrid zone between chromosome races. Mamm Biol 71, 257–267 (2006). https://doi.org/10.1016/j.mambio.2006.02.004
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DOI: https://doi.org/10.1016/j.mambio.2006.02.004