Data from: Species recognition limits mating between hybridizing ant species

<p><span>Identifying mechanisms limiting hybridization is a central goal of speciation research. Here, we studied pre-mating and post-mating barriers to hybridization between two ant species, <em>Formica selysi</em> and <em>Formica cinerea</em>. These species hybridize in the Rhône valley in Switzerland, where they form a mosaic hybrid zone, with limited introgression from <em>F. selysi</em> into <em>F</em>. <em>cinerea</em>. 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 post-mating 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 non-hybrid workers. To gain insights into the cues involved in species recognition, we analyzed the cuticular hydrocarbons of queens, males and workers and staged dyadic encounters between workers. Cuticular hydrocarbon profiles differed markedly between species, but were similar in <em>F. cinerea</em> and hybrids. Accordingly, workers also discriminated species, but they did not discriminate <em>F. cinerea</em> and hybrids. We discuss how the CHC-based recognition system of ants may facilitate the establishment of pre-mating barriers to hybridization, independent of hybridization costs.</span></p>