Genomic patterns of adaptive divergence between chromosomally differentiated sunflower species.
Genomic patterns of adaptive divergence between chromosomally differentiated sunflower species.
复制标题
染色体分化的向日葵物种之间适应性分歧的基因组模式。
DOI：
10.1093/molbev/msp043
复制
发表时间：
2009
影响因子：
10.7
通讯作者：
Rieseberg,LorenH
中科院分区：
文献类型：
--
作者：
Strasburg,JaredL;Scotti-Saintagne,Caroline;Scotti,Ivan;Lai,Zhao;Rieseberg,LorenH
了解物种形成的遗传机制和物种差异的基础是进化生物学中最重要的挑战之一。特别感兴趣的两个问题是什么样的角色分歧选择和染色体分化在这些过程中发挥作用。最近提出的一些理论认为，染色体重排可以通过抑制重排区域内的重组来促进生殖隔离和物种差异的发展和维持。减少重组允许等位基因的积累，有助于隔离和适应性分化，并保护现有的差异，从渐渗的影响，早期物种之间。在这里，我们使用分布在这两个物种基因组中的77个基因座的序列数据，研究了两个广泛分布、广泛杂交的向日葵物种向日葵和向日葵叶柄向日葵的重排与共线区域的遗传多样性和分歧模式。我们发现弱的证据增加染色体断裂点附近的遗传分化，但不是在重排区域的整体。我们没有发现证据表明重排染色体上的适应性分歧率增加;事实上，共线染色体显示出两个物种之间固定氨基酸差异的更大过剩。与第三种向日葵的比较表明，H。annuusandH.小叶柄可能发生在其形成期间或之后不久。我们的研究结果表明，染色体重排在遗传分化中的作用有限，但它们确实记录了大量的适应性分化，并提供了进一步的证据，证明了在广泛的杂交和基因流动中，物种的完整性和遗传特性如何在许多位点得以保持。
Understanding the genetic mechanisms of speciation and basis of species differences is among the most important challenges in evolutionary biology. Two questions of particular interest are what roles divergent selection and chromosomal differentiation play in these processes. A number of recently proposed theories argue that chromosomal rearrangements can facilitate the development and maintenance of reproductive isolation and species differences by suppressing recombination within rearranged regions. Reduced recombination permits the accumulation of alleles contributing to isolation and adaptive differentiation and protects existing differences from the homogenizing effects of introgression between incipient species. Here, we examine patterns of genetic diversity and divergence in rearranged versus collinear regions in two widespread, extensively hybridizing sunflower species,Helianthus annuusandHelianthus petiolaris, using sequence data from 77 loci distributed throughout the genomes of the two species. We find weak evidence for increased genetic divergence near chromosomal break points but not within rearranged regions overall. We find no evidence for increased rates of adaptive divergence on rearranged chromosomes; in fact, collinear chromosomes show a far greater excess of fixed amino acid differences between the two species. A comparison with a third sunflower species indicates that much of the nonsynonymous divergence betweenH. annuusandH. petiolarisprobably occurred during or soon after their formation. Our results suggest a limited role for chromosomal rearrangements in genetic divergence, but they do document substantial adaptive divergence and provide further evidence of how species integrity and genetic identity can be maintained at many loci in the face of extensive hybridization and gene flow.