No Synergy Needed: Ecological Constraints Favor the Evolution of Eusociality

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Online enhancements: appendixes.abstract: In eusocial species, some individuals sacrifice their own reproduction for the benefit of others. It has been argued that the evolution of sterile helpers in eusocial insects requires synergistic efficiency gains through cooperation that are uncommon in cooperatively breeding vertebrates and that this precludes a universal ecological explanation of social systems with alloparental care. In contrast, using a model that incorporates realistic ecological mechanisms of population regulation, we show here that constraints on independent breeding (through nest-site limitation and dispersal mortality) eliminate any need for synergistic efficiency gains: sterile helpers may evolve even if they are relatively inefficient at rearing siblings, reducing their colony's per-capita productivity. Our approach connects research fields by using hypotheses developed for cooperative breeding to explain the evolution of eusociality. The results suggest that these hypotheses may apply more generally than previously thought.

The evolution of eusociality: no risk‐return tradeoff but the ecology matters

“…Our analysis shows that assumptions about life history and ecology, not just genetic relatedness, matter critically when considering both the origin and elaboration of eusociality (see also Korb & Heinze ; Fromhage & Kokko ; Nonacs , ; Avila & Fromhage ). The risk‐return tradeoff proposed at the origin of eusociality by Fu et al .…”

“…Trivers & Hare 1976;Seger 1983;Boomsma 2009;Fromhage & Kokko 2011;Nonacs 2011Nonacs , 2014Gardner et al 2012;Quinones & Pen 2017;Rautiala et al 2019). It remains equivocal, however, whether relatedness really was unusually high in the ancestors of today's eusocial taxa (Nonacs 2011;Pernu & Helantera 2019), and the ecological parameters in Hamilton's Rule are potentially just as important determinants of whether helping or solitary nesting is the optimal strategy (Queller 1994(Queller , 1996Field et al 2000;Korb & Heinze 2008;Avila & Fromhage 2015). Recent models suggest that two features of life history and ecology have a critical impact on whether eusociality evolves: the potential for workers to take over egg-laying following the queen's death, and the relationship between group size and productivity (Fromhage & Kokko 2011;Nonacs 2011Nonacs , 2019Fu et al 2015).…”

Sex allocation conflict and sexual selection throughout the lifespan of eusocial colonies

“…Current models that study the emergence of eusociality that explicitly track colony growth usually fix the switch from ergonomic to reproductive phase to happen at arbitrary size of the colony (e.g. Avila and Fromhage, 2015). Hence, extending our model to study evolution of eusociality could explain how life-history interacts with other mechanisms that are known to drive the evolution of eusociality.…”

Invasion fitness, inclusive fitness, and reproductive numbers in heterogeneous populations

“…Dispersal may occur between groups by individuals alone or by groups of individuals (i.e., propagule dispersal), but dispersal is always assumed to be uniform between groups in the population; in other words, we consider an island model of dispersal (Wright 1931). This setup allows us to represent classical models where the group state determines local group size, such as metapopulation processes (e.g., Chesson 1981;Metz and Gyllenberg 2001;Rousset and Ronce 2004), insect colony dynamics (e.g., Frank 1998;Avila and Fromhage 2015), compartmentalized replication like in the stochastic corrector model for prebiotic evolution (e.g., Szathmary and Demeter 1987;Grey et al 1995), or when the state determines the local abiotic environment in a group (e.g., Greenwood-Lee and Taylor 2001;Wild et al 2009;Rodrigues and Gardner 2012).…”