Plant Diversity and Conservation Group, Centro de Botânica Aplicada à Agricultura (CBAA), Instituto Superior de Agronomia (ISA), Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
BMC Plant Biol. 2013 Dec 6;13:205. doi: 10.1186/1471-2229-13-205.
The genus Limonium Miller comprises annual and perennial halophytes that can produce sexual and/or asexual seeds (apomixis). Genetic and epigenetic (DNA methylation) variation patterns were investigated in populations of three phenotypically similar putative sexual diploid species (L. nydeggeri, L. ovalifolium, L. lanceolatum), one sexual tetraploid species (L. vulgare) and two apomict tetraploid species thought to be related (L. dodartii, L. multiflorum). The extent of morphological differentiation between these species was assessed using ten diagnostic morphometric characters.
A discriminant analysis using the morphometric variables reliably assigns individuals into their respective species groups. We found that only modest genetic and epigenetic differentiation was revealed between species by Methylation Sensitive Amplification Polymorphism (MSAP). However, whilst there was little separation possible between ploidy levels on the basis of genetic profiles, there was clear and pronounced interploidy discrimination on the basis of epigenetic profiles. Here we investigate the relative contribution of genetic and epigenetic factors in explaining the complex phenotypic variability seen in problematic taxonomic groups such as Limonium that operate both apomixis and sexual modes of reproduction.
Our results suggest that epigenetic variation might be one of the drivers of the phenotypic divergence between diploid and tetraploid taxa and discuss that intergenome silencing offers a plausible mechanistic explanation for the observed phenotypic divergence between these microspecies. These results also suggest that epigenetic profiling offer an additional tool to infer ploidy level in stored specimens and that stable epigenetic change may play an important role in apomict evolution and species recognition.
Limonium Miller 属包含一年生和多年生盐生植物，能够产生有性和/或无性种子（无融合生殖）。本研究调查了三个表型相似的假定有性二倍体物种（L. nydeggeri、L. ovalifolium 和 L. lanceolatum）、一个有性四倍体物种（L. vulgare）和两个被认为相关的无融合生殖四倍体物种（L. dodartii 和 L. multiflorum）的种群中的遗传和表观遗传（DNA 甲基化）变异模式。使用十个诊断形态计量特征评估这些物种之间的形态分化程度。
使用形态计量变量的判别分析可靠地将个体分配到各自的物种组中。我们发现，通过甲基化敏感扩增多态性（MSAP），物种之间仅显示出适度的遗传和表观遗传分化。然而，尽管基于遗传谱很难在倍性水平之间进行分离，但基于表观遗传谱可以清楚地进行种间区分。在这里，我们研究了遗传和表观遗传因素在解释 Limonium 等具有复杂表型变异的问题分类群中的相对贡献，这些分类群同时具有无融合生殖和有性繁殖的方式。
我们的结果表明，表观遗传变异可能是二倍体和四倍体分类群之间表型分歧的驱动因素之一，并讨论了基因组间沉默为观察到的这些微种之间的表型分歧提供了一个合理的机制解释。这些结果还表明，表观遗传分析提供了一种推断存储标本倍性水平的额外工具，并且稳定的表观遗传变化可能在无融合生殖进化和物种识别中发挥重要作用。
