Opinion
Differentiated Social Relationships and the Pace-of-Life-History

https://doi.org/10.1016/j.tree.2021.02.007Get rights and content

Highlights

  • Costs and benefits of social relationships depend on life-history strategies.

  • Social bonds are more likely to evolve in species with slow life histories.

  • Pace-of-life syndromes may mean that slower individuals have stronger social bonds.

  • Life-history can explain variation in social relationships across taxonomic scales.

When selection is imposed by both social and ecological environments, the costs and benefits of social relationships can depend on life-history strategy. We argue that the formation and maintenance of differentiated social relationships will prevail in species and individuals with slow life histories. Social behaviours that benefit survival can promote slower life histories. Meanwhile, longer lifespan promotes the development of strong and stable social bonds by allowing fitness payoffs to be postponed. Differentiated social behaviours should be favoured for fast life histories only when they promote the rate of reproduction. Finally, associations between life-history strategies and other traits (e.g., personality) provide a mechanism to drive inter-individual variation in social relationships, making life-history important for sociality across taxonomic scales.

Section snippets

Importance of Social Relationships in Animal Societies

There is a huge diversity of social systems in wild populations [1., 2., 3., 4.], and social structure plays an important role in broader ecological and evolutionary processes such as disease transmission, culture, and cooperation [1]. Individuals of many species aggregate, associate or interact with each other for reasons that include foraging, mating, gathering information and reducing predation risk [2]. Social structure in these groups can range from fluid aggregations involving many

Selection in Fast and Slow Species

The fast–slow continuum (pace-of-life) describes an organism’s investment in survival and reproduction and is a principal axis of life-history variation [29,30]. Fast organisms have high reproductive rates but invest less in survival so die at a faster rate. Slow organisms are long-lived (underpinned by genomic differences [31,32]) but have lower reproductive rates. While other axes of life-history variation are important, the fast–slow continuum explains most variation in animal life histories

Interspecific Variation in Social Relationships across the Fast–Slow Continuum

Social relationships are likely to generate different fitness returns for fast and slow species. Lifespan differences influence the opportunity for differentiated social relationships to be beneficial, while the relative importance of social embeddedness in promoting or buffering survival and reproductive rate also influences the strength of selection for different life-history strategies. Indirect evolutionary relationships may also play a role. For example, associations between cognitive

Pace-of-Life Syndromes and Interindividual Variation in Social Relationships

The importance of the fast–slow continuum as an axis of interspecific variation in life-history traits is well established [33]. However, within a population, individuals can also vary in their life histories, perhaps associated with behavioural or cognitive traits that influence their social relationships. While the four direct mechanisms outlined in the previous section can also apply at an individual level (e.g., longer-lived individuals have more time on average to develop stronger

Measuring the Association between Pace-of-Life and Social Relationships

Life-history strategies have close evolutionary correlations with other traits, meaning that comparative analyses are complicated by collinearity. To provide one example, body size is closely related to pace-of-life [63] and might also be associated with differentiated social relationships if it changes the costs and benefits of forming stable, long-term social relationships (e.g., through injury risk during contests). Typically, there is sufficient variation around these dependencies to be

Concluding Remarks and Future Perspectives

Life-history variation along the fast–slow continuum is a strong candidate mechanism to explain variation in social behaviour across taxonomic scales. We argue that differentiated social relationships are more prevalent among slow-living species and individuals, particularly when they improve survival. To test this prediction will require the application of comparative approaches that exploit newly available life-history and social network databases [66,67]; theoretical work that considers the

Acknowledgements

M.J.S. is funded by the University of Exeter. We thank Megan Thompson, Sam Ellis, Dave Hosken, Mike Cant, and Tom Tregenza and three reviewers for helpful advice, discussion and comments.

Declaration of Interests

The authors declare no conflicts of interest.

Glossary

Differentiated social relationship
behaviour that means an individual splits its social capital among fewer individuals (i.e., has a few strong connections rather than many weaker connections) or divides its social capital less equitably between the same number of contacts. This results in a position in a social network characterised by high variability in the strength of connections to others.
Fast–slow continuum
a key axis of life-history variation that explains differences in how genotypes

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