1 ǀ Introduction
In many animals, offspring dispersal is critical to avoid local resource competition and the risk of inbreeding. Given that dispersal is often dangerous and young individuals have limited knowledge about the specific conditions in their surroundings, parents may assist their young during dispersal. For example, poison frogs may transfer tadpoles from land to water (Pašukonis et al., 2019), wolf spiders may carry spiderlings (Bonte et al., 2007), and mother bats teach their offspring to navigate and find suitable habitats (Goldshtein et al., 2022). Similarly, in several species of ants, workers accompany and even carry young queens during the founding of new colonies away from their natal nests (e.g., Möglich & Hölldobler, 1974; Fernández-Escudero et al., 2001; Peeters & Aron, 2017).
In the ant Cardiocondyla elegans, workers may carry their female sexual sisters over several meters and dump them into the nest entrance of another colony. We have argued that this peculiar behavior constitutes a type of assisted dispersal and mate choice, allowing young queens to outbreed with several unrelated males away from their natal nests (Vidal et al., 2021). The ant genus Cardiocondyla is characterized by an ancestral male polyphenism with winged disperser males and wingless “ergatoid” males, which locally mate with female sexuals eclosing in their natal nests. Colonies of most tropicalCardiocondyla are relatively small, with only a few dozen workers and one or several queens. Individual wingless males are therefore capable of monopolizing mating with all female sexuals by aggressively excluding other males with their shear- or sickle-shaped mandibles. In contrast, colonies of Palearctic species are typically much larger, with several hundred workers and obligatorily a single, multiply mated queen. Furthermore, female sexuals are produced not year-round as in the tropics but seasonally. Because of this, wingless males are no longer capable of individually securing copulations with all female sexuals and indeed have evolved mutual tolerance (Heinze, 2017). As mating occurs in the natal nest, inbreeding coefficients determined from microsatellite genotypes are relatively high. Nevertheless, data suggest that 40 to 80 % of matings involve unrelated sexuals (Schrempf et al., 2005; Lenoir et al., 2007; Schrempf, 2014; Vidal et al., 2021), and observations in the field revealed that in C. elegans these are facilitated by “royal matchmaking” by the workers, which transfer female sexuals between unrelated nests.
Here, we follow up on our earlier studies and provide new data about queen carrying in the field, the relatedness among carrier and carried ants, and the growth rate of colonies started by individual queens after mating only with brothers, one or multiple unrelated males. We expected that outbreeding and multiple mating are reflected in a better performance of colonies, i.e., faster colony growth.
2 ǀ Material and Methods