Maintenance of species boundaries despite rampant hybridization between three species of reef fishes (Hexagrammidae): implications for the role of selection
Maintenance of species boundaries despite rampant hybridization between three species of reef fishes (Hexagrammidae): implications for the role of selection
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DOI：
10.1111/j.1095-8312.2007.00786.x
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发表时间：
2007-05-01
影响因子：
1.9
通讯作者：
Bernardi, Giacomo
中科院分区：
文献类型：
--
作者：
Crow, Karen D.;Munehara, Hiroyuki;Bernardi, Giacomo
杂交和渐渗对物种形成过程是拮抗的。如果杂交种能够存活并回交，遗传渗入将减缓或阻止种群间生殖隔离的进化。如果种间在二次接触时杂交，渗入将最终侵蚀种间边界。如果杂交猖獗，基因流动高，杂交比例将接近随机交配所期望的值，并且遗传渗入将克服物种边界，使种群均质化。或者，如果物种在遗传上是不同的，那么通过随机交配，杂交的比例将大大低于预期，基因流动将被对杂交的选择所中断，并且F-1杂交或回交将无法生存或不育。在这里，我们研究一个具有这两种相反情景所期望的特征的系统。杂交发生在三种礁鱼之间的属六鳃鳗在一个分布重叠的区域意想不到的高频率。检测到回交个体，表明F-1杂交种是可行的，能够繁殖。然而，这些物种在多个基因座上具有遗传差异。为了研究这个明显的悖论，我们使用一个线粒体和两个核标记来估计杂交的相对比例、对称模式、不生存和细胞核不平衡。在这个系统中，为了维持物种边界，我们在不同的生活史阶段调用了对杂交的选择。(c) 2007年伦敦林奈学会。
Hybridization and introgression are antagonistic to the process of speciation. If hybrids are viable and backcross, introgression will slow or prevent the evolution of reproductive isolation between populations. If species hybridize upon secondary contact, introgression will ultimately erode species boundaries. If hybridization is rampant and gene flow is high, the proportion of hybrids will approach values expected with random mating, and introgression will overcome species boundaries, homogenizing populations. Alternatively, if species are genetically distinct, the proportion of hybrids would be significantly less than expected with random mating, gene flow would be interrupted by selection against hybrids, and inviability or sterility of F-1 hybrids or backcrosses would be expected. Here, we investigate a system with characteristics expected by both of these opposing scenarios. Hybridization occurs between three species of reef fishes in the genus Hexagrammos at unexpected high frequencies in a zone of distributional overlap. Backcrossed individuals are detected, indicating F-1 hybrids are viable and capable of reproducing. Yet, these species are genetically distinct at multiple loci. To study this apparent paradox, we estimate the relative proportions of hybrids, patterns of symmetry, inviability, and cytonuclear disequilibria using one mitochondrial and two nuclear markers. We invoke selection against hybrids, at various life history stages, in the maintenance of species boundaries in this system. (c) 2007 The Linnean Society of London.