A biogeographic genetic approach for testing the role of reinforcement:: The case of Drosophila pseudoobscura and D-persimilis
A biogeographic genetic approach for testing the role of reinforcement:: The case of Drosophila pseudoobscura and D-persimilis
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DOI：
10.1111/j.0014-3820.2000.tb00021.x
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发表时间：
2000-02-01
期刊：
影响因子：
3.3
通讯作者：
Singh, RS
中科院分区：
文献类型：
--
作者：
Kulathinal, RJ;Singh, RS
强化在物种形成中的作用可以用两种不同的模型来解释。在模型I中，两个分歧的群体杂交并产生成功回交的可育杂交种（具有基因流的杂交）。在LT模型中，两个群体杂交，但随后的回交是非生产性的（没有基因流的杂交）。利用Drosophila persimilis和D. pseudobscura，我们已经测试了模型I通过比较异源基因渗入同域与异域种群的程度。我们表明，这种特定的模型的强化，这是基于杂交和基因如何不同的人群之间的二次接触后，在这两个物种中没有实现的某些期望。这些证据包括同域和异域异种种群之间的遗传距离以及独特/稀有等位基因比例的相似性以及异种种群之间的遗传距离和地理距离之间的负相关性，这表明生态分化。这种量化差异基因流的方法对利用遗传距离比较同域隔离和异域隔离的研究具有重要意义。根据模型I，人们可以预期，与具有相同遗传距离的异域物种相比，同域物种的前合子隔离模式更高，这仅仅是由于同域种群之间的基因渗入而低估了遗传距离的结果。我们建议更简约的解释，如强化没有遗传交换（模型II）和生态分化，这需要高水平的预先存在的种群之间的生殖隔离。
The role of reinforcement in speciation can be explained by two distinct models. In model I, two diverged populations hybridize and produce fertile hybrids that successfully backcross (hybridization with gene flow). In model LT, two populations hybridize but succeeding backcrosses are unproductive (hybridization without gene flow). Using Drosophila persimilis and D. pseudoobscura, we have tested model I by comparing the extent of heterospecific introgression in sympatric versus allopatric populations. We show that certain expectations of this particular model of reinforcement, which is based on hybridization and gene how between divergent populations after secondary contact, are not realized in these two species. The evidence consists of the similarity of genetic distances as well as proportions of unique/rare alleles between sympatric and allopatric heterospecific populations and a negative correlation between genetic distance and geographical distance between heterospecific populations, which suggests ecological differentiation. This approach in quantifying differential gene flow has important consequences to studies that compare sympatric and allopatric isolation using genetic distance. Following model I, one would expect a pattern of higher prezygotic isolation in sympatric species compared to allopatric species of the same genetic distance simply as a result of an underestimation of genetic distance due to introgression between sympatric populations. We suggest more parsimonious explanations such as reinforcement without genetic exchange (model II) and ecological differentiation, which require high levels of preexisting reproductive isolation between populations.