Twyman KZ & Gardner A (in press) A formal theory of group-level adaptation for obligate eusociality. Journal of Evolutionary Biology.
Darwin argued that natural selection leads organisms to appear as if they are striving to maximise their fitness. This idea is readily recognised at the individual cell or body level, but such adaptive design may also manifest at some higher levels of biological organisation. Previous work has formalised the idea that social groups can be viewed as adaptive individuals in their own right—i.e., ‘superorganisms’—under the assumptions that within-group selection is absent and that there is no class structure. However, the original and most common biological use of the term ‘superorganism’ is in reference to insect colonies in which members exhibit striking class structure in the form of reproductive division of labour. Accordingly, although obligately eusocial colonies are regularly conceptualised as having the capacity for colony-level adaptation, current formalisms are unable to support this idea. Here, we develop a formal theory of group-level adaptation for obligately eusocial colonies by establishing mathematical correspondences that connect the dynamics of natural selection—as described by Price’s equation—to the mathematics of optimisation—wherein the colony is considered a fitness-maximising agent—under a range of assumptions as to which members of the colony control its phenotype and the degree to which they are genetically related. (Image: Gemini)