Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, August Thienemannstrasse 2, 24306 Ploen, Germany.
Evolution. 2012 Feb;66(2):443-58. doi: 10.1111/j.1558-5646.2011.01445.x. Epub 2011 Sep 29.
Barriers to gene flow between naturally hybridizing taxa reveal the initial stages of speciation. Reduced hybrid fertility is a common feature of reproductive barriers separating recently diverged species. In house mice (Mus musculus), hybrid male sterility has been studied extensively using experimental crosses between subspecies. Here, we present the first detailed picture of hybrid male fertility in the European M. m. domesticus-M. m. musculus hybrid zone. Complete sterility appears rare or absent in natural hybrids but a large proportion of males (~30%) have sperm count or relative testis weight below the range in pure subspecies, and likely suffer reduced fertility. Comparison of a suite of traits related to fertility among subfertile males indicates reduced hybrid fertility in the contact zone is highly variable among individuals and ancestry groups in the type, number, and severity of spermatogenesis defects present. Taken together, these results suggest multiple underlying genetic incompatibilities are segregating in the hybrid zone, which likely contribute to reproductive isolation between subspecies.
自然杂交类群之间基因流动的障碍揭示了物种形成的初始阶段。杂种生育力降低是分离最近分化物种的生殖障碍的常见特征。在小家鼠（Mus musculus）中，亚种间的实验杂交已经广泛研究了杂种雄性不育。在这里，我们首次详细描述了欧洲 M. m. domesticus-M. m. musculus 杂种带的杂种雄性生育力。在自然杂种中，完全不育似乎很少见或不存在，但很大一部分雄性（约 30%）的精子数或相对睾丸重量低于纯亚种的范围，可能生育力降低。对一系列与生育力相关的特征进行比较表明，在接触区，杂种生育力在个体间和祖先群体间存在高度的可变性，表现在精子发生缺陷的类型、数量和严重程度上。总之，这些结果表明，杂种带中存在多种潜在的遗传不相容性，这可能有助于亚种间的生殖隔离。
