Carson Evan W, Dowling Thomas E
School of Life Sciences, Arizona State University, Tempe, 85287-4501, USA.
Mol Ecol. 2006 Mar;15(3):667-79. doi: 10.1111/j.1365-294X.2005.02763.x.
The evolutionary importance of hybridization in animals has been subject of much debate. In this study, we examined the influence of hydrogeographic history and hybridization on the present distribution of nuclear and mitochondrial DNA variation in two pupfish species, Cyprinodon atrorus and Cyprinodon bifasciatus. Results presented here indicate that there has been limited introgression of nuclear genes; however, mtDNA introgression has been substantial, with complete replacement of the C. bifasciatus mitochondrial genome by that of C. atrorus. Subsequent to this replacement, there has been diversification of mitochondrial haplotypes along major geographic regions in the basin. Evidence was also found that mitochondrial replacement follows a predictable, cyclical pattern in this system, with isolation and diversification followed by re-contact and replacement of C. bifasciatus mitochondrial haplotypes by those of C. atrorus. This pattern is best explained by a combination of a numeric bias towards C. atrorus and mating site selection rather than selection for C. atrorus mitochondrial genome. These results demonstrate the important role hybridization can play in evolution.
杂交在动物进化中的重要性一直是诸多争论的主题。在本研究中，我们考察了水文地理历史和杂交对两种鳉鱼（暗鳉和双带鳉）目前核DNA和线粒体DNA变异分布的影响。此处呈现的结果表明，核基因的渐渗有限；然而，线粒体DNA的渐渗却很显著，暗鳉的线粒体基因组完全取代了双带鳉的线粒体基因组。在这种取代之后，流域内主要地理区域的线粒体单倍型出现了多样化。我们还发现，在这个系统中，线粒体取代遵循一种可预测的循环模式，先是隔离和多样化，随后是重新接触，暗鳉的线粒体单倍型取代双带鳉的线粒体单倍型。这种模式的最佳解释是对暗鳉的数量偏差和交配位点选择的结合，而非对暗鳉线粒体基因组的选择。这些结果证明了杂交在进化中可以发挥的重要作用。
