Natural hybridisation is now recognised as pervasive in its occurrence across the Tree of Life. Resurgent interest in natural hybridisation fuelled by developments in genomics has led to an improved understanding of the genetic factors that promote or prevent species cross-mating. Despite this body of work overturning many widely held assumptions about the genetic barriers to hybridisation, it is still widely thought that ploidy differences between species will be an absolute barrier to hybridisation and introgression. Here, we revisit this assumption, reviewing findings from surveys of polyploidy and hybridisation in the wild. In a case study in the British flora, 203 hybrids representing 35% of hybrids with suitable data have formed via cross-ploidy matings, while a wider literature search revealed 59 studies (56 in plants and 3 in animals) in which cross-ploidy hybridisation has been confirmed with genetic data. These results show cross-ploidy hybridisation is readily overlooked, and potentially common in some groups. General findings from these studies include strong directionality of hybridisation, with introgression usually towards the higher ploidy parent, and cross-ploidy hybridisation being more likely to involve allopolyploids than autopolyploids. Evidence for adaptive introgression across a ploidy barrier and cases of cross-ploidy hybrid speciation shows the potential for important evolutionary outcomes.

中文翻译：

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跨倍性杂交和基因渗入的重要性日益显现

现在，自然杂交被认为在生命之树中普遍存在。基因组学的发展推动了人们对自然杂交的兴趣重新燃起，人们对促进或阻止物种交叉交配的遗传因素有了更深入的了解。尽管这项工作推翻了许多关于杂交遗传障碍的广泛持有的假设，但人们仍然普遍认为物种之间的倍性差异将是杂交和基因渗入的绝对障碍。在这里，我们重新审视这一假设，回顾多倍体和野生杂交的调查结果。在英国植物区系的一项案例研究中，通过跨倍性交配形成了 203 个杂交种，占具有合适数据的杂交种的 35%，而更广泛的文献检索显示了 59 项研究（56 项在植物中，3 项在动物中），其中跨倍性杂交已被基因数据证实。这些结果表明，跨倍性杂交很容易被忽视，并且在某些群体中可能很常见。这些研究的一般发现包括杂交的强烈方向性，基因渗入通常朝向更高倍性亲本，并且跨倍性杂交更有可能涉及异源多倍体而不是同源多倍体。跨越倍性屏障的适应性渐渗的证据和跨倍性杂交物种形成的案例表明了重要进化结果的潜力。