Models of social evolution: can we do better to predict ‘who helps whom to achieve what’?

Abstract

Models of social evolution and the evolution of helping have been classified in numerous ways. Two categorical differences have, however, escaped attention in the field. Models tend not to justify why they use a particular assumption structure about who helps whom: a large number of authors model peer-to-peer cooperation of essentially identical individuals, probably for reasons of mathematical convenience; others are inspired by particular cooperatively breeding species, and tend to assume unidirectional help where subordinates help a dominant breed more efficiently. Choices regarding what the help achieves (i.e. which life-history trait of the helped individual is improved) are similarly made without much comment: fecundity benefits are much more commonly modelled than survival enhancements, despite evidence that these may interact when the helped individual can perform life-history reallocations (load-lightening and related phenomena). We review our current theoretical understanding of effects revealed when explicitly asking ‘who helps whom to achieve what’, from models of mutual aid in partnerships to the very few models that explicitly contrast the strength of selection to help enhance another individual's fecundity or survival. As a result of idiosyncratic modelling choices in contemporary literature, including the varying degree to which demographic consequences are made explicit, there is surprisingly little agreement on what types of help are predicted to evolve most easily. We outline promising future directions to fill this gap.

Correlated pay-offs are key to cooperation

“…Reciprocity, the third potential cause of correlated pay-offs, is arguably the most contended possibility to generate cooperation and altruism [12,32]. It is the theme of this article and a focus of many contributions to this special issue of the Philosophical Transactions [7,[33][34][35][36][37].…”

Ecological succession, patch age and the evolution of social behaviour and terminal investment

“…The evolution of social behaviour in a demographic context has received a substantial amount of attention over the past few years (Lehmann and Rousset , Rodrigues and Kokko ). To a large extent, however, this work assumes that local habitats have an infinite lifespan, whereby patches are perpetually colonised, have an endless supply of resources, and are immune to ecological disturbances.…”

“…Above, I have considered that dispersal was a fixed model parameter. Sometimes, this may be an implausible assumption, as dispersal often changes with local environmental conditions, in general, and with patch age, in particular, as observed in many species (Crespi and Taylor , Roff , Korb and Lenz , 2005, Clobert et al 2009, , Ronce and Clobert , Aguillon and Duckworth ) and suggested by multiple theoretical studies (Crespi and Taylor , Roff , Olivieri et al 1995, 2005, Kisdi et al , Rodrigues and Johnstone , Rodrigues and Gardner ). To investigate this biological scenario, I now consider that production of public goods co‐evolves with the dispersal of individuals.…”

“…Termites, for instance, use an elaborated mechanism for detecting the frequency of vibro‐acoustic signals to estimate the amount of food still available in their colonies (Evans et al 2005), and as the amount of locally available resources becomes depleted, the number of alate primary reproductives increases (Korb and Katrantzis ). In addition, while most models assume individual colonisation of patches, in many instances, dispersal assumes a clonal or group mode of colonisation, a factor that has a significant impact on the genetic structure of the population (Gandon and Michalakis 1999), and on the evolution of cooperation (Jacob et al ).…”

“…Modelling the force of kin selection under complex demographic and ecological conditions presents significant challenges (Rousset and Ronce , Rousset , Lehmann et al 2006, Rodrigues and Gardner ). Modelling kin selection under successional dynamics, in particular, requires not only extinction–colonisation dynamics but also patch‐age dynamics in a population where groups are relatively small so that kin selection becomes a significant force driving evolutionary change.…”