López de Heredia Unai, Mora-Márquez Fernando, Goicoechea Pablo G, Guillardín-Calvo Laura, Simeone Marco C, Soto Álvaro
G.I. Genética, Fisiología e Historia Forestal, Dpto. Sistemas y Recursos Naturales, ETSI Montes, Forestal y del Medio Natural, Universidad Politécnica de Madrid, Madrid, Spain.
Department of Forestry, NEIKER-BRA, Vitoria-Gasteiz, Spain.
Front Plant Sci. 2020 Sep 4;11:564414. doi: 10.3389/fpls.2020.564414. eCollection 2020.
Hybridization and its relevance is a hot topic in ecology and evolutionary biology. Interspecific gene flow may play a key role in species adaptation to environmental change, as well as in the survival of endangered populations. Despite the fact that hybridization is quite common in plants, many hybridizing species, such as spp., maintain their integrity, while precise determination of genomic boundaries between species remains elusive. Novel high throughput sequencing techniques have opened up new perspectives in the comparative analysis of genomes and in the study of historical and current interspecific gene flow. In this work, we applied ddRADseq technique and developed an bioinformatics pipeline for the study of ongoing hybridization between two relevant Mediterranean oaks, and . We adopted a local scale approach, analyzing adult hybrids () identified in a mixed stand and their open-pollinated progenies. We have identified up to 9,435 markers across the genome and have estimated individual introgression levels in adults and seedlings. Estimated contribution of to the genome is higher, on average, in hybrid progenies than in hybrid adults, suggesting preferential backcrossing with this parental species, maybe followed by selection during juvenile stages against individuals with higher genomic contribution. Most discriminating markers seem to be scattered throughout the genome, suggesting that a large number of small genomic regions underlie boundaries between these species. A noticeable proportion of the markers (26%) showed allelic frequencies in adult hybrids very similar to one of the parental species, and very different from the other; a finding that seems relevant for understanding the hybridization process and the occurrence of adaptive introgression. Candidate marker databases developed in this study constitute a valuable resource to design large scale re-sequencing experiments in Mediterranean sclerophyllous oak species and could provide insight in species boundaries and on adaptive introgression between and
杂交及其相关性是生态学和进化生物学中的一个热门话题。种间基因流动可能在物种适应环境变化以及濒危种群的生存中发挥关键作用。尽管杂交在植物中相当普遍，但许多杂交物种，如 spp.，仍保持其完整性，而物种间基因组边界的精确确定仍然难以捉摸。新型高通量测序技术为基因组的比较分析以及历史和当前种间基因流动的研究开辟了新的视角。在这项工作中，我们应用了ddRADseq技术，并开发了一种生物信息学流程，用于研究两种相关的地中海栎树 和 之间正在进行的杂交。我们采用了局部尺度的方法，分析了在混交林中鉴定出的成年杂种（）及其自由授粉的后代。我们在全基因组中鉴定出了多达9435个标记，并估计了成年个体和幼苗中的个体渐渗水平。平均而言，在杂交后代中， 对基因组的估计贡献高于杂交成年个体，这表明与该亲本物种存在优先回交现象，随后可能在幼年期对具有较高 基因组贡献的个体进行选择。大多数具有区分性的标记似乎分散在整个基因组中，这表明这些物种之间的边界由大量小的基因组区域构成。相当比例的标记（26%）在成年杂种中的等位基因频率与亲本物种之一非常相似，而与另一个亲本物种非常不同；这一发现似乎与理解杂交过程和适应性渐渗的发生有关。本研究中开发的候选标记数据库是设计地中海硬叶栎树种大规模重测序实验的宝贵资源，并且可以为 和 之间的物种边界以及适应性渐渗提供见解。
