Independent allopatric polyploidizations shaped the geographical structure and initial stage of reproductive isolation in an allotetraploid fern, Lepisorus nigripes (Polypodiaceae)
Independent allopatric polyploidizations shaped the geographical structure and initial stage of reproductive isolation in an allotetraploid fern, Lepisorus nigripes (Polypodiaceae)
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DOI：
10.1371/journal.pone.0233095
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发表时间：
2020-05
期刊：
影响因子：
3.7
通讯作者：
Tao Fujiwara;Yasuyuki Watano
中科院分区：
文献类型：
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作者：
Tao Fujiwara;Yasuyuki Watano
虽然多倍体是普遍存在的，其进化意义已经被认识到，但尚不清楚新形成的多倍体物种是如何形成的。特别是，多个起源对多倍体物种种群间遗传分化的影响以及独立起源的谱系是否具有不同的进化潜力仍然是悬而未决的问题。我们使用种群遗传学和系统发育的方法来鉴定异源四倍体蕨类植物Lepisorus nigripe中具有独立起源的谱系之间的遗传分化。在整个分布范围内，共收集到51个种群的352只个体。为了检验遗传结构，利用单拷贝核基因进行了多位点基因分型、贝叶斯群体结构分析和邻域网络分析。构建了系统发育树以检测重复的多倍体起源。分析败育孢子的比例作为合子后生殖隔离的指标。东型和西型两种不同的遗传谱系主要分布在日本群岛的东部和西部。系统发育分析表明，这些类型的起源是独立的，并在每种类型中发现了额外的独立起源。我们还揭示了两种类型之间有限的基因重组，甚至在它们的共域区域也是如此。东方型和西方型的F1杂种表现出育性下降。东西方类型很可能分别在日本东部和西部独立形成。杂交种的有限遗传重组和育性降低表明，这两种类型正处于物种形成的早期阶段。两个地理来源独立的多倍体家系可形成生殖隔离障碍(S)。
Although polyploidy is pervasive and its evolutionary significance has been recognized, it remains unclear how newly formed polyploid species become established. In particular, the impact of multiple origins on genetic differentiation among populations of a polyploid species and whether lineages of independent origins have different evolutionary potentials remain open questions. We used population genetic and phylogenetic approaches to identify genetic differentiation between lineages with independent origins within an allotetraploid fern, Lepisorus nigripes. A total of 352 individuals from 51 populations were collected throughout the distribution range. To examine the genetic structure, multilocus genotyping, Bayesian population structure analysis, and neighbor-net analysis were carried out using single-copy nuclear genes. Phylogenetic trees were constructed to detect recurrent polyploid origins. Proportions of abortive spores were analysed as the measure of postzygotic reproductive isolation. Two genetically distinct lineages, the East-type and the West-type, were distributed mainly in the eastern and western parts, respectively, of the Japanese archipelago. Phylogenetic analyses indicated independent origins of these types and detected additional independent origins within each type. We also revealed limited genetic recombination between both types, even in their sympatric regions. F1 hybrids between the East- and West-types showed a reduction in fertility. It is likely that the East- and West-types formed independently in the eastern and western parts of Japan, respectively. The limited genetic recombination and reduced fertility of hybrids suggest that the two types are at an incipient stage of speciation. Two polyploid lineages with independent geographic origins could develop reproductive isolation barrier(s).