Conclusion
Although inbreeding avoidance is an appealing concept in evolutionary biology, evidence is scarce for its widespread occurrence (de Boeret al. 2021), with mate choice ranging from inbreeding preference to tolerance to avoidance (Szulkin et al. 2013). This variability is observed both within and between species, and is related to the strength of inbreeding depression (Fox & Reed 2011). Individuals would not be selected to avoid mating with a related partner if the chance and costs of inbreeding are low and if the costs associated with nestmate discrimination are high (Kokko et al. 2006). For example, our findings may not apply to most social Hymenoptera, due to the extra cost of inbreeding resulting from their haplodiploid sex determination, in which a single founding queen cannot afford the burden of producing 50% workless and sterile diploid males (Ross & Fletcher 1986; Zayed & Packer 2005). In contrast, the common occurrence of inbreeding among neotenics in mature termite colonies suggests a lower level of inbreeding depression. Overall, our findings emphasize the varied and changing costs of outbreeding and inbreeding play out over the lifespan of termite colonies. Investigating this variation and its costs will surely provide insights into the evolutionary mechanisms driving inbreeding avoidance and preference in social insects.
ACKNOWLEDGEMENTS
We are grateful to C. Aguero and M. N. Moran for their help in incipient colony establishment, as well as with the microbial loads experiments. We thank M. Bulmer for providing the Metarhizium fungal strains. This work was supported by the Urban Entomology Endowment at Texas A&M University.
AUTHOR CONTRIBUTIONS
PAE and ELV designed the study. PAE collected the samples, performed the experiments and analyzed the data. PAE wrote the paper with contributions of ELV.
DATA AVAILABILITY STATEMENT
The data reported in this study will be deposited in the Open Science Framework database upon acceptance,https://osf.io (DOI XX).
SUPPLEMENTARY MATERIAL