种间杂交可以导致基因或基因组在种间渗透以及分类上的混乱。张亚平院士，云南大学于黎研究员和博士生刘江通过分析124个中国兔鼠物种个体的线粒体基因和核基因序列，第一次发现在6个中国兔属物种间存在着通过种间杂交而导致的基因渗透。令人惊奇的是，东北兔的线粒体完全被来自雪兔和华南兔的线粒体所替代。此外，核基因分析发现在中国兔属物种间存在高比例的杂合子，在多个物种间有共享单倍型，提示中国兔属物种间的核基因的渗透是一个正在发生的过程。因此，推测由频繁的杂交事件所导致的形态上的过渡类型以及非典型的线粒体基因组世系的存在可能是导致中国兔属物种分类混乱的真正原因。
该研究结果近期发表在BMC Evolutionary Biology刊物上。(生物谷 Bioon.com)
doi:BMC Evolutionary Biology 2011, 11:223
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Reticulate evolution: frequent introgressive hybridization among Chinese hares (genus Lepus) revealed by analyses of multiple mitochondrial and nuclear DNA loci
Jiang LiuLi YuMichael ArnoldChun-Hua WuShi-Fang WuXin LuYa-Ping Zhang
Interspecific hybridization may lead to the introgression of genes and genomes across species barriers and contribute to a reticulate evolutionary pattern and thus taxonomic uncertainties. Since several previous studies have demonstrated that introgressive hybridization has occurred among some species within Lepus, therefore it is possible that introgressive hybridization events also occur among Chinese Lepus species and contribute to the current taxonomic confusion. Results: Data from four mtDNA genes, from 116 individuals, and one nuclear gene, from 119 individuals, provides the first evidence of frequent introgression events via historical and recent interspecific hybridizations among six Chinese Lepus species. Remarkably, the mtDNA of L. mandshuricus was completely replaced by mtDNA from L. timidus and L. sinensis. Analysis of the nuclear DNA sequence revealed a high proportion of heterozygous genotypes containing alleles from two divergent clades and that several haplotypes were shared among species, suggesting repeated and recent introgression. Furthermore, results from the present analyses suggest that Chinese hares belong to eight species. Conclusion: This study provides a framework for understanding the patterns of speciation and the taxonomy of this clade. The existence of morphological intermediates and atypical mitochondrial gene genealogies resulting from frequent hybridization events likely contribute to the current taxonomic confusion of Chinese hares. The present study also demonstrated that nuclear gene sequence could offer a powerful complementary data set with mtDNA in tracing a complete evolutionary history of recently diverged species.
