Genetic divergence with ongoing gene flow is maintained by the use of different hosts in phytophagous ladybird beetles genus Henosepilachna
Genetic divergence with ongoing gene flow is maintained by the use of different hosts in phytophagous ladybird beetles genus Henosepilachna
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DOI：
10.1111/jeb.13071
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发表时间：
2017-06-01
影响因子：
2.1
通讯作者：
Katakura, H.
中科院分区：
文献类型：
--
作者：
Matsubayashi, K. W.;Kohyama, T. I.;Katakura, H.
即使在基因流动存在的情况下，对不同环境的适应也会通过自然选择促进种群分化——这种现象通常发生在生态物种形成过程中。为了阐明自然选择在物种形成过程中如何促进和维持种群差异，我们研究了亲缘关系较近的三种日本食植物瓢虫：Henosepilachna pustulosa、H. niponica和H. yasutomii的种群遗传结构、基因流动程度和异质性基因组差异。这些物种作为一个通才，一个野蓟（Cirsium spp.）专家和一个蓝升麻（Caulophyllum robustum）专家分别，他们的范围不同。这两种特殊物种广泛共存，但由于它们对特定寄主植物的高度专门化，因此在生殖上完全隔离。全基因组扩增片段长度多态性（AFLP）标记和线粒体细胞色素c氧化酶亚基I （COI）基因序列显示出与地理距离和生态差异相关的明显的全基因组差异。然而，对AFLP位点和线粒体序列的杂交评估显示，这两个同域特有种之间存在一定程度的单向基因流动。基于所有可变AFLP位点的主坐标分析（PCoA）表明，无论物种（即宿主范围）如何，相邻地点的群体之间存在遗传相似性。然而，进一步的比较基因组扫描发现了一小部分基因座，约占所有基因座的1%，是不同宿主相关的异常值。这些结果表明，这三个物种具有复杂的起源，可能被当前的基因流所掩盖，并且即使在同域物种对之间存在一定程度的基因流时，只有一小部分基因组与不同的宿主使用有关，也可以维持生态分化。
Adaptation to different environments can promote population divergence via natural selection even in the presence of gene flow-a phenomenon that typically occurs during ecological speciation. To elucidate how natural selection promotes and maintains population divergence during speciation, we investigated the population genetic structure, degree of gene flow and heterogeneous genomic divergence in three closely related Japanese phytophagous ladybird beetles: Henosepilachna pustulosa, H. niponica and H. yasutomii. These species act as a generalist, a wild thistle (Cirsium spp.) specialist and a blue cohosh (Caulophyllum robustum) specialist, respectively, and their ranges differ accordingly. The two specialist species widely co-occur but are reproductively isolated solely due to their high specialization to a particular host plant. Genomewide amplified fragment-length polymorphism (AFLP) markers and mitochondrial cytochrome c oxidase subunit I (COI) gene sequences demonstrated obvious genomewide divergence associated with both geographic distance and ecological divergence. However, a hybridization assessment for both AFLP loci and the mitochondrial sequences revealed a certain degree of unidirectional gene flow between the two sympatric specialist species. Principal coordinates analysis (PCoA) based on all of the variable AFLP loci demonstrated that there are genetic similarities between populations from adjacent localities irrespective of the species (i.e. host range). However, a further comparative genome scan identified a few fractions of loci representing approximately 1% of all loci as different host-associated outliers. These results suggest that these three species had a complex origin, which could be obscured by current gene flow, and that ecological divergence can be maintained with only a small fraction of the genome is related to different host use even when there is a certain degree of gene flow between sympatric species pairs.