Offspring survival
Our results show that incipient colonies may suffer from inbreeding when facing pathogen pressure. Although cuticular microbial loads did not differ between inbred and outbred offspring in our study, the increased susceptibility of inbred offspring is consistent with higher microbial loads in inbred colonies of Z. angusticollis , potentially resulting from reduced grooming or a less diverse range of antimicrobials (Calleri et al. 2006). Notably, our results on incipient colonies contrast with those uncovered on mature field colonies of the same species, showing a weak influence of genetic diversity toward entomopathogens (Aguero et al. 2020; Agueroet al. 2021b). First, this difference may stem from a greater reduction in heterozygosity in the present study compared to those in mature colonies, where heterozygosity was only moderately reduced by neotenic reproduction (Rosengaus & Traniello 2001; Aguero et al.2021b). Similarly, offspring in the present study were probably younger and thus more susceptible to pathogen exposure []; they were also reared under lab conditions and did not face the same pathogen exposure as workers collected from the field, therefore removing the possibility that immune priming may potentially mask differences between inbred and outbred groups (Rosengaus et al. 1999; Rosengaus et al.2007). Despite these differences, the better survival of particular pairings also support the suggestion that the influence of a specific genetic background may be greater than the overall genetic diversity on colony survival (Aguero et al. 2020; Aguero et al. 2021b). Together with previous findings, our results reveal that inbreeding is a negligible factor in the survival of both founding couples and mature colonies; but may have an important role in incipient colonies. These findings indicate that higher inbreeding depression during colony development, where incipient colonies may be more vulnerable, could increase the proportion of mature colonies headed by outbred reproductives (DeHeer & Vargo 2006) (illustrated in Figure 6).