Departement of Ecology and Evolution, University of Lausanne, Lausanne, CH-1015, Switzerland.
Department of Entomology, University of California, Riverside, California, 92521, USA.
Evolution. 2022 Sep;76(9):2105-2115. doi: 10.1111/evo.14566. Epub 2022 Jul 19.
Identifying mechanisms limiting hybridization is a central goal of speciation research. Here, we studied premating and postmating barriers to hybridization between two ant species, Formica selysi and Formica cinerea. These species hybridize in the Rhône valley in Switzerland, where they form a mosaic hybrid zone, with limited introgression from F. selysi into F. cinerea. There was no sign of temporal isolation between the two species in the production of queens and males. With choice experiments, we showed that queens and males strongly prefer to mate with conspecifics. Yet, we did not detect postmating barriers caused by genetic incompatibilities. Specifically, hybrids of all sexes and castes were found in the field and F1 hybrid workers did not show reduced viability compared to nonhybrid workers. To gain insights into the cues involved in species recognition, we analyzed the cuticular hydrocarbons (CHCs) of queens, males, and workers and staged dyadic encounters between workers. CHC profiles differed markedly between species, but were similar in F. cinerea and hybrids. Accordingly, workers also discriminated species, but they did not discriminate F. cinerea and hybrids. We discuss how the CHC-based recognition system of ants may facilitate the establishment of premating barriers to hybridization, independent of hybridization costs.
确定限制杂交的机制是物种形成研究的核心目标。在这里，我们研究了两种蚂蚁物种 Formica selysi 和 Formica cinerea 之间的交配前和交配后杂交障碍。这两个物种在瑞士的罗纳河谷杂交，形成一个镶嵌杂交带，来自 F. selysi 的基因渐渗很少进入 F. cinerea。在女王和雄性的产生中，这两个物种没有时间隔离的迹象。通过选择实验，我们表明女王和雄性强烈倾向于与同种交配。然而，我们没有发现由遗传不相容引起的交配后障碍。具体来说，在野外发现了所有性别和级别的杂种，并且与非杂种工蚁相比，F1 杂种工蚁的生存能力并没有降低。为了深入了解物种识别涉及的线索，我们分析了女王、雄性和工蚁的表皮碳氢化合物 (CHC)，并在工蚁之间进行了二元接触实验。CHC 图谱在物种之间差异显著，但在 F. cinerea 和杂种中相似。因此，工蚁也能区分物种，但它们不能区分 F. cinerea 和杂种。我们讨论了蚂蚁基于 CHC 的识别系统如何在不考虑杂交成本的情况下促进杂交前的交配障碍的建立。
