Data from: Introgressive hybridization as a promoter of genome reshuffling in natural homoploid fish hybrids (Cyprinidae, Leuciscinae)

Understanding the mechanisms underlying diversification and speciation by introgressive hybridization is currently one of the major challenges in evolutionary biology. Here, the analysis of hybridization between two pairs of Iberian Leuciscinae provided new data on independent hybrid zones involving Achondrostoma oligolepis (AOL) and Pseudochondrostoma duriense (PDU), and confirmed the occurrence of hybrids between AOL and Pseudochondrostoma polylepis (PPO). A multilevel survey combining morphological, genetic and cytogenomic markers on a vast population screening successfully sorted the selected fishes as admixed. Results were similar in both AOL × PDU and AOL × PPO systems. Overall, hybrid morphotypes, cytogenomic data and genetic profiling indicated preferential backcrossing and suggested AOL as a major genomic contributor. Moreover, results implied AOL as more permissive to introgression than PDU or PPO. Although PDU- and PPO-like individuals appeared more resilient to genome modifications, AOL appeared to be more involved and affected by the ongoing hybridization events, as chromosomal translocations were only found in AOL-like individuals. All hybrids analysed evidenced extensive ribosomal DNA (rDNA) polymorphism that was not found in parental species, but usually seen falling within the range of possible parental combinations. Yet, transgressive phenotypes that cannot be explained by normal recombination, including more rDNA clusters than expected or the occurrence of syntenic rDNAs, were also detected. Present results proved rapid genomic evolution providing the genetic novelty for species to persist. In addition, although the ultimate consequences of such apparently extensive and recurrent events remain unknown, modern genome-wide methodologies are of great promise towards answering questions concerning the causes, dynamics and impacts of hybridization.解析渐渗杂交（introgressive hybridization）驱动的物种多样化与物种形成背后的机制，是当前进化生物学领域的核心挑战之一。本研究对两群伊比利亚雅罗鱼亚科（Iberian Leuciscinae）鱼类的杂交事件展开分析，为涉及寡鳞无鳍鱼（Achondrostoma oligolepis, AOL）与杜氏假无鳍鱼（Pseudochondrostoma duriense, PDU）的独立杂交带提供了全新数据，并证实了AOL与多鳞假无鳍鱼（Pseudochondrostoma polylepis, PPO）之间存在杂交个体。研究通过大规模种群筛查，结合形态学、遗传学与细胞基因组学标记开展多维度分析，成功将筛选出的鱼类个体鉴定为杂交后代。AOL×PDU与AOL×PPO两个杂交体系的分析结果高度一致。整体而言，杂交形态型、细胞基因组学数据与遗传分型均显示出偏向回交的杂交模式，并提示AOL为主要的基因组贡献者。此外，研究结果还表明，相较于PDU或PPO，AOL更易发生基因组渐渗。尽管PDU样与PPO样个体对基因组改造的抗性更强，但AOL更深度参与并受当前杂交事件的影响——仅在AOL样个体中发现了染色体易位。所有被分析的杂交个体均表现出丰富的核糖体DNA（ribosomal DNA, rDNA）多态性，这一特征在亲本物种中并未出现，但通常符合亲本基因组组合的理论范围。同时，研究还检测到无法通过正常重组解释的超亲表型，包括超出预期数量的rDNA簇，以及共线性核糖体DNA（syntenic rDNAs）的出现。本研究结果证实了快速基因组演化可为物种存续提供遗传创新。此外，尽管这类广泛且反复发生的杂交事件的最终演化后果仍不明确，但现代全基因组研究方法为解答杂交的成因、动态过程与影响等核心问题提供了极具前景的研究路径。