Genetic diversity defines the evolutionary potential of a species, yet mounting evidence suggests that epigenetic diversity could also contribute to adaptation. Elucidating the complex interplay between genetic and epigenetic variation in wild populations remains a challenge for evolutionary biologists, and the intriguing possibility that epigenetic diversity could compensate for the loss of genetic diversity is one aspect that remains basically unexplored in wild plants. This hypothesis is addressed in this paper by comparing the extent and patterns of genetic and epigenetic diversity of phylogenetically closely related but ecologically disparate species. Seven pairs of congeneric species from Cazorla mountains in south-eastern Spain were studied, each pair consisting of one endemic, restricted-range species associated to stressful environments, and one widespread species occupying more favourable habitats. The prediction was tested that endemic species should have lower genetic diversity due to population fragmentation, and higher epigenetic diversity induced by environmental stress, than their widespread congeners. Genetic (DNA sequence variants) and epigenetic (DNA cytosine methylation variants) diversities and their possible co-variation were assessed in three populations of each focal species using amplified fragment length polymorphism (AFLP) and methylation-sensitive AFLP (MSAP). All species and populations exhibited moderate to high levels of genetic polymorphism irrespective of their ecological characteristics. Epigenetic diversity was greater than genetic diversity in all cases. Only in endemic species were the two variables positively related, but the difference between epigenetic and genetic diversity was greater at populations with low genetic polymorphism. Results revealed that the relationship between genetic and epigenetic diversity can be more complex than envisaged by the simple hypothesis addressed in this study, and highlight the need of additional research on the actual role of epigenetic variation as a source of phenotypic diversity before a realistic understanding of the evolutionary relevance of epigenetic phenomena in plant adaptation can be achieved.

中文翻译：

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伊比利亚山脉东南部分布范围不同的同域、密切相关的植物对的遗传和表观遗传多样性比较。

遗传多样性决定了一个物种的进化潜力，但越来越多的证据表明表观遗传多样性也可能有助于适应。阐明野生种群遗传和表观遗传变异之间复杂的相互作用仍然是进化生物学家面临的一个挑战，而表观遗传多样性可以补偿遗传多样性丧失的有趣可能性是野生植物中基本上尚未探索的一个方面。本文通过比较系统发育密切相关但生态上不同的物种的遗传和表观遗传多样性的程度和模式来解决这一假设。研究人员对来自西班牙东南部卡索拉山脉的七对同属物种进行了研究，每对由一种与压力环境相关的特有、限制范围物种和一种占据更有利栖息地的广泛物种组成。该预测经过检验，与广泛分布的同类相比，特有物种由于种群破碎而具有较低的遗传多样性，而环境压力引起的表观遗传多样性较高。使用扩增片段长度多态性 (AFLP) 和甲基化敏感 AFLP (MSAP) 评估每个焦点物种的三个种群的遗传（DNA 序列变异）和表观遗传（DNA 胞嘧啶甲基化变异）多样性及其可能的共变异。所有物种和种群均表现出中等到高水平的遗传多态性，无论其生态特征如何。在所有情况下，表观遗传多样性都大于遗传多样性。仅在特有物种中，这两个变量呈正相关，但在遗传多态性较低的种群中，表观遗传和遗传多样性之间的差异更大。结果表明，遗传和表观遗传多样性之间的关系可能比本研究中提出的简单假设所设想的更为复杂，并强调在现实理解表观遗传变异作为表型多样性来源之前，需要对表观遗传变异作为表型多样性来源的实际作用进行额外的研究。可以实现植物适应中表观遗传现象的进化相关性。