Ecol Evol. 2012 Feb;2(2):379-96. doi: 10.1002/ece3.92.
Recent multilocus studies of congeneric birds have shown a pattern of elevated interspecific divergence on the Z chromosome compared to the autosomes. In contrast, intraspecifically, birds exhibit less polymorphism on the Z chromosome relative to the autosomes. We show that the four black-and-white Ficedula flycatcher species show greater genetic divergence on the Z chromosome than on the autosomes, and that the ratios of intraspecific polymorphism at Z-linked versus autosomal markers are below the neutral expectation of 75%. In all species pairs, we found more fixed substitutions and fewer shared polymorphisms on the Z chromosome than on the autosomes. Finally, using isolation with migration (IMa) models we estimated gene flow among the four closely related flycatcher species. The results suggest that different pattern of evolution of Z chromosomes and autosomes is best explained by the faster-Z hypothesis, since the estimated long-term gene flow parameters were close to zero in all comparisons.
近期对同种鸟类的多位点研究表明，与常染色体相比，Z 染色体上的种间差异较大。相比之下，种内的 Z 染色体上的多态性相对于常染色体来说较少。我们发现四种黑白斑姬鹟的 Z 染色体上的遗传差异大于常染色体，而且 Z 连锁标记与常染色体标记之间的种内多态性比值低于中性预期的 75%。在所有物种对中，我们发现 Z 染色体上的固定替换比常染色体多，而共享多态性比常染色体少。最后，我们使用带有迁移的隔离（IMa）模型估计了这四种密切相关的姬鹟之间的基因流。结果表明，Z 染色体和常染色体不同的进化模式最好用“更快的 Z 染色体假说”来解释，因为在所有比较中，估计的长期基因流参数都接近零。
