Toward greater realism in inclusive fitness models : the case of caste fate conflict in insect societies
Ferreira, Helena Mendes (Zoological Institute, KU Leuven)
Alves, Denise Araujo (Universidade de São Paulo)
Cool, Lloyd (Zoological Institute, KU Leuven)
Oi, Cintia Akemi (Zoological Institute, KU Leuven)
Caliari Oliveira, Ricardo (Universitat Autònoma de Barcelona. Departament de Biologia Animal, de Biologia Vegetal i d'Ecologia)
Wenseleers, Tom (Zoological Institute, KU Leuven)

Data:	2024
Resum:	In the field of social evolution, inclusive fitness theory has been successful in making a wide range of qualitative predictions on expected patterns of cooperation and conflict. Nevertheless, outside of sex ratio theory, inclusive fitness models that make accurate quantitative predictions remain relatively rare. Past models dealing with caste fate conflict in insect societies, for example, successfully predicted that if female larvae can control their own caste fate, an excess should opt to selfishly develop as queens. Available models, however, were unable to accurately predict levels of queen production observed in Melipona bees-a genus of stingless bees where caste is self-determined-as empirically observed levels of queen production are approximately two times lower than the theoretically predicted ones. Here, we show that this discrepancy can be resolved by explicitly deriving the colony-level cost of queen overproduction from a dynamic model of colony growth, requiring the incorporation of parameters of colony growth and demography, such as the per-capita rate at which new brood cells are built and provisioned, the percentage of the queen's eggs that are female, costs linked with worker reproduction and worker mortality. Our revised model predicts queen overproduction to more severely impact colony productivity, resulting in an evolutionarily stable strategy that is approximately half that of the original model, and is shown to accurately predict actual levels of queen overproduction observed in different Melipona species. Altogether, this shows how inclusive fitness models can provide accurate quantitative predictions, provided that costs and benefits are modeled in sufficient detail and are measured precisely. In a fascinating new study, scientists from the Laboratory of Socio-ecology and Social Evolution at the University of Leuven delve into conflicts linked with the choice to become either a queen or a worker in bee societies. Focusing on stingless bees and honeybees, they explore how the ability to control one's own caste fate can result in many choosing to become queens. In particular, the authors show that in Melipona stingless bees, where caste is self-determined, about 10% of all females selfishly opt to become queens, while in related species where caste is nutritionally determined, queens are found to be produced at a rate that aligns with colony needs. The researchers further develop a theoretical model that accurately predicts levels of queen production in these Melipona bees, showing that an evolutionary equilibrium is reached when the individual benefit of becoming a queen balances with the collective cost that would occur if too many became queens and too few workers would be produced. This work provides a compelling example of the power of evolutionary theory in making accurate predictions in the field of social evolution, and offers new insights into how conflicts between individual and collective interests play out in animal societies.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Caste fate conflict ; Inclusive fitness theory ; Social evolution ; Stingless bees
Publicat a:	Evolution Letters, Vol. 8, Num. 3 (June 2024) , p. 387-396, ISSN 2056-3744

DOI: 10.1093/evlett/qrad068
PMID: 38818418

10 p, 6.0 MB

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