Big thistle eats the little thistle: does unidirectional introgressive hybridization endanger the conservation of Onopordum hinojense?
Big thistle eats the little thistle: does unidirectional introgressive hybridization endanger the conservation of Onopordum hinojense?
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DOI：
10.1111/nph.13156
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发表时间：
2015-04-01
期刊：
影响因子：
9.4
通讯作者：
Talavera, Salvador
中科院分区：
文献类型：
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作者：
Balao, Francisco;Casimiro-Soriguer, Ramon;Talavera, Salvador
杂交在植物进化中具有创造性作用，这是众所周知的。然而，它也可能对亲本物种产生负面影响。蓝刺头属（Onopordum）是一个大属，其物种经常杂交。在伊比利亚半岛西南部，稀有的伊诺琼蓝刺头（O. hinojense）与广泛分布的显脉蓝刺头（O. nervosum）共同存在，这两个类群之间的杂交种被描述为奥努本蓝刺头（O. xonubense）。在这项研究中，我们利用形态学和细胞遗传学特征分析以及遗传标记和种群动态模型，确定了杂交区中杂交种和亲本的灭绝风险。为了研究基因渗入过程，我们使用了扩增片段长度多态性（AFLP）标记、贝叶斯分析和基因组扫描方法。形态学、基因组大小和分子标记证实了同倍体杂交，并且还表明F - 1杂交种与显脉蓝刺头的单向回交，这可能会使花粉粒较小且结实率极低（8%）的伊诺琼蓝刺头亲本被淹没。基因组扫描方法揭示了几个显著偏离中性的基因座。最后，我们的种群动态模型表明，显脉蓝刺头较高的适合度通过种群淹没威胁到伊诺琼蓝刺头的生存。我们的研究为单向基因渗入和种群淹没导致快速灭绝的情景提供了有力的新证据。这里所使用的多层面方法为基因渗入在植物灭绝中的作用提供了新的见解。
Hybridization is known to have a creative role in plant evolution. However, it can also have negative effects on parental species. Onopordum is a large genus whose species frequently hybridize. In the Southwest Iberian Peninsula, the rare O.hinojense co-occurs with the widely distributed O.nervosum, and hybrids between these two taxa have been described as O.xonubense. In this study we determine the extinction risk in a hybrid zone, both for hybrids and parentals, using analyses of morphological and cytogenetic traits as well as genetic markers and demographic models. To investigate the introgression process we used amplified fragment length polymorphism (AFLP) markers, Bayesian analyses and genome scan methods. Morphology, genome size and molecular markers confirmed homoploid hybridization and also indicated unidirectional backcrossing of F-1 hybrids with O.nervosum, which is likely to swamp O.hinojense, the parental with lower pollen size and a very low fruit set (8%). Genome scan methods revealed several loci significantly deviating from neutrality. Finally, our demographic modeling indicated that the higher fitness of O.nervosum threats the survival of O.hinojense by demographic swamping. Our study provides strong new evidence for a scenario of rapid extinction by unidirectional introgression and demographic swamping. The multifaceted approach used here sheds new light on the role of introgression in plant extinctions.