Data from: Hybridisation in closely related Rhododendron species: half of all species differentiating markers experience serious transmission ratio distortion

An increasing number of studies of hybridization in recent years have revealed that complete reproductive isolation between species is frequently not finalized in more or less closely related organisms. Most of these species do, however, seem to retain their phenotypical characteristics despite the implication of gene flow, highlighting the remaining gap in our knowledge of how much of an organism's genome is permeable to gene flow, and which factors promote or prevent hybridization. We used AFLP markers to investigate the genetic composition of three populations involving two interfertile Rhododendron species: two sympatric populations, of which only one contained hybrids, and a further hybrid-dominated population. No fixed differences between the species were found, and only 5.8% of the markers showed some degree of species differentiation. Additionally, 45.5% of highly species-differentiating markers experienced significant transmission distortion in the hybrids, which was most pronounced in F1 hybrids, suggesting that factors conveying incompatibilities are still segregating within the species. Furthermore, the two hybrid populations showed stark contrasting composition of hybrids; one was an asymmetrically backcrossing hybrid swarm, while in the other, backcrosses were absent, thus preventing gene flow.

近年来，诸多有关杂交（hybridization）的研究均表明，亲缘关系相近的生物类群间，物种间的完全生殖隔离（reproductive isolation）往往并未最终建立。然而，即便存在基因流（gene flow）的渗透，多数此类物种仍能维持自身的表型特征，这也暴露出当前研究的空白：我们尚未明确生物体基因组中究竟有多大比例可被基因流渗透，以及哪些因素会促进或阻碍杂交过程。本研究借助AFLP标记，对涉及两个可互育杜鹃属（Rhododendron）物种的三个种群的遗传组成进行分析：两个同域分布种群（其中仅一个种群存在杂交个体），以及一个以杂交个体为优势类群的种群。研究未检测到物种间存在固定遗传差异，仅5.8%的标记表现出一定程度的物种分化特征。此外，45.5%的高物种分化标记在杂交个体中呈现出显著的传递偏倚（transmission distortion），该现象在F1杂种（F1）中最为突出，表明导致生殖不相容的相关因子仍在物种内处于分离状态。进一步而言，两个杂交种群的杂交个体组成呈现出显著差异：一个为不对称回交杂交群，另一个则完全不存在回交个体，从而阻断了基因流。