Data from: Interspecific crossing and genetic mapping reveal intrinsic genomic incompatibility between two Senecio species that form a hybrid zone on Mount Etna, Sicily

Studies of hybridizing species can reveal much about the genetic basis and maintenance of species divergence in the face of gene flow. Here we report a genetic segregation and linkage analysis conducted on F2 progeny of a reciprocal cross between Senecio aethnensis and S. chrysanthemifolius that form a hybrid zone on Mount Etna, Sicily, aimed at determining the genetic basis of intrinsic hybrid barriers between them. Significant transmission ratio distortion (TRD) was detected at 34 (~27%) of 127 marker loci located in nine distinct clusters across seven of the ten linkage groups detected, indicating genomic incompatibility between the species. TRD at these loci could not be attributed entirely to post-zygotic selective loss of F2 individuals that failed to germinate or flower (16.7 %). At four loci tests indicated that pre-zygotic events, such as meiotic drive in F1 parents or gametophytic selection, contributed to TRD. Additional tests revealed that cytonuclear incompatibility contributed to TRD at five loci, Bateson- Dobzhansky-Muller (BDM) incompatibilities involving epistatic interactions between loci contributed to TRD at four loci, and underdominance (heterozygote disadvantage) was a possible cause of TRD at one locus. Major chromosomal rearrangements were probably not a cause of interspecific incompatibility at the scale that could be examined with current map marker density. Intrinsic genomic incompatibility between S. aethnensis and S. chrysanthemifolius revealed by TRD across multiple genomic regions in early generation hybrids is likely to impact the genetic structure of the natural hybrid zone on Mount Etna by limiting introgression and promoting divergence across the genome.

针对杂交物种的研究可深入揭示基因流背景下物种分化的遗传基础及其维持机制。本研究针对西西里岛埃特纳火山上形成天然杂交带的埃特纳千里光（*Senecio aethnensis*）与菊叶千里光（*Senecio chrysanthemifolius*）的互交F₂后代开展遗传分离与连锁分析，旨在阐明二者间内在生殖隔离的遗传基础。在本次检测到的10个连锁群中的7个上，共9个独立基因座簇内的127个标记基因座中，有34个（约27%）呈现显著的传递比率偏倚（transmission ratio distortion, TRD），表明两物种间存在基因组不相容性。此类基因座的TRD并非完全由合子后选择淘汰未萌发或未开花的F₂个体所致，该类淘汰个体占比达16.7%。对4个基因座的分析显示，合子前事件（如F₁亲本的减数分裂驱动或配子体选择）是TRD的诱因之一。进一步分析表明，5个基因座的TRD由核质不相容性介导；4个基因座的TRD涉及基因座间上位互作的贝特森-多布赞斯基-穆勒（Bateson-Dobzhansky-Muller, BDM）不相容性；另有1个基因座的TRD可能由下位显性（underdominance，杂合子劣势）引发。基于当前图谱标记密度的检测范围，大规模染色体重排大概率并非两物种间生殖不相容性的诱因。本研究通过早期世代杂种中多个基因组区域的TRD现象，揭示了埃特纳千里光与菊叶千里光间的内在基因组不相容性；该不相容性可通过限制基因渐渗、推动全基因组分化，进而影响埃特纳火山天然杂交带的遗传结构。