Data from: Widespread hybridization within mound-building wood ants in Southern Finland results in cytonuclear mismatches and potential for sex-specific hybrid breakdown

Hybridization and gene flow between diverging lineages is increasingly recognized as a common evolutionary process and its consequences can vary from hybrid breakdown to adaptive introgression. We have previously found a population of wood ant hybrids between Formica aquilonia and F. polyctena that shows antagonistic effects of hybridization: females with introgressed alleles show hybrid vigour, whereas males with the same alleles show hybrid breakdown. Here we investigate whether hybridization is a general phenomenon in this species pair, and analyze 647 worker samples from 16 localities in Finland using microsatellite markers and a 1200 bp mitochondrial sequence. Our results show that 27 sampled nests contained parental-like gene pools (six putative F. polyctena and 21 putative F. aquilonia) and all remaining nests (69), from nine localities, contained hybrids of varying degrees. Patterns of genetic variation suggest these hybrids arise from several hybridization events or, instead, have backcrossed to the parental gene pools to varying extents. In contrast to expectations, the mitochondrial haplotypes of the parental species were not randomly distributed among the hybrids. Instead, nests that were closer to parental-like F. aquilonia for nuclear markers preferentially had F. polyctena's mitochondria and vice versa. This systematic pattern suggests there may be underlying selection favoring cytonuclear mismatch and hybridization. We also found a new hybrid locality with strong genetic differences between the sexes similar to those predicted under antagonistic selection on male and female hybrids. Further studies are needed to determine the selective forces that act on male and female genomes in these newly discovered hybrids.

分化支系间的杂交与基因流日益被认为是一类常见的进化过程，其演化后果可从杂交衰退延伸至适应性基因渐渗。我们此前曾发现一个木蚁（wood ant）杂交种群，其亲本为红褐林蚁（Formica aquilonia）与多栉蚁（Formica polyctena，原文缩写为F. polyctena），该种群展现出杂交的拮抗效应：携带渐渗等位基因的雌蚁表现出杂交优势，而携带相同等位基因的雄蚁则出现杂交衰退。
本研究旨在验证杂交现象在该物种对中是否具有普遍性，并利用微卫星标记（microsatellite markers）与一段1200 bp的线粒体序列（mitochondrial sequence），对芬兰境内16个采样位点的647份工蚁样本开展分析。
研究结果显示，27个采样蚁巢具备类亲本基因库特征（其中推定多栉蚁蚁巢6个、推定红褐林蚁蚁巢21个），剩余来自9个采样位点的69个蚁巢均携带不同程度的杂交个体。遗传变异模式表明，此类杂交个体要么源于多次独立杂交事件，要么在不同程度上与亲本基因库发生了回交。
与预期相悖的是，亲本物种的线粒体单倍型并未在杂交个体中随机分布。具体而言，在核标记上更接近类亲本红褐林蚁的蚁巢，其线粒体单倍型多来自多栉蚁，反之亦然。这种系统性分布格局提示，可能存在潜在的选择作用以维持核质不匹配与杂交状态。
此外，我们还发现了一处新的杂交采样位点，其雌雄个体间存在显著的遗传差异，与雌雄杂交个体受拮抗选择作用的理论预测相符。
未来仍需开展进一步研究，以明确作用于这些新发现杂交种群雌雄基因组的选择压力。