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Godoy, I., Korsten, P. & Perry, S.E. Genetic, maternal, and environmental influences on sociality in a pedigreed primate population. Heredity 129, 203–214 (2022). https://doi.org/10.1038/s41437-022-00558-6
Understanding the different factors that influence sociality (the degree to which individuals in an animal population tend to associate in social groups and form cooperative societies) is vital to understanding and predicting the evolvability of a species. The following study is one of the first to analyse genetic and non-genetic influences on social behaviour in a primate separately, whilst accounting for common environmental effects. This is because untwining genetic and non-genetic sources of variation in social behaviours is challenging since closely related organisms usually have shared social environments. This study combined a multi-generational recorded ancestry and two decades of observational data on white-faced capuchin monkeys (Cebus capucinus imitator) to look at the social, genetic, and environmental influences on sociality.
Repeatability in social behaviour implies that group-living individuals show individual and stable tendencies in solving social problems and interacting with other group members. This study revealed that repeatability is largely accounted for by additive genetic sources of variation (traits that are attributed to two or more genes). It also showed similarities between siblings for the same, known as maternal effects. However, maternal effects were minimal in comparison to additive genetic sources. Such results are surprising in species such as capuchins, which have prolonged maternal care. Generally, however, it was found that maternal effects explain half as much variance in traits as do additive genetic effects.
Variance in sociality was also accounted for through factors such as group of residence (the particular group/clan that the studied capuchin was a part of). Variance in total time spent socially and the number of partners was evident between groups, independent from group sizes. This finding is significant as it revealed that some groups are consistently more social across years than others, which may reveal why some outcompete others. Hence, the evolvability of a species must be looked at a group level along with the individual level.
Seasonality (the quality or fact of varying with or depending on the season or time of year) had little impact on sociality, but there was found to be strong evidence for the influence of ENSO phases. The El Niño-Southern Oscillation (ENSO) is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean. El Niño (typically producing drier seasons) and La Niña (typically producing wetter seasons) phases were both associated with reduced sociality scores. Drought conditions during El Niño phases were more likely to drive individuals farther apart as they spent more time searching for scarce resources. La Niña phases may also have led to changes in how individuals cluster near others. However, heavy rainfall affected visibility in the field, reflecting underestimations of sociality.
Group size and the interaction between age and sex also affected sociality. It decreased with increasing age. It was also found that juvenile males were more social than juvenile females, especially in early development. However, these differences dissipated by adulthood. An adult from a large group was also more social than one from a small group, though the differences were not dramatic. Maternal effects were found to be stronger in the juvenile versus adult stages of development.
Whilst this study provided much new insight into the causes of variation of sociability, and hence evolvability, it had limitations. The phenotype (physical trait expressed by a gene) of one individual can be influenced by the genes expressed in others. The social environment in which an individual finds itself is a combination of the expression of genes from potential partners. These indirect genetic effects are a source of genetic variation that can both constrain or facilitate an evolutionary response to the selection of a trait, and they haven’t been explored in this study. However, the basis for this study has led to studies investigating the contribution of additive genetic effects to the gut microbiome and estimating rates of evolution in wild animal populations.
Works Cited
Oxford Languages. “Oxford Languages and Google – English.” Oxford Languages, Oxford University Press, languages.oup.com/google-dictionary-en/. Accessed 7 Mar. 2023.
Tkaczynski, Patrick J., et al. “Long-Term Repeatability in Social Behaviour Suggests Stable Social Phenotypes in Wild Chimpanzees.” Royal Society Open Science, vol. 7, no. 8, Aug. 2020, p. 200454, https://doi.org/10.1098/rsos.200454. Accessed 10 Feb. 2023.
US Department of Commerce, NOAA. “What Is ENSO?” Www.weather.gov,
http://www.weather.gov/mhx/ensowhat#:~:text=The%20El%20Ni%C3%B1o%2DSouthern%20Oscillation. Accessed 7 Mar. 2023.
Wikipedia Contributors. “Sociality.” Wikipedia, Wikimedia Foundation, 9 Dec. 2019, en.wikipedia.org/wiki/Sociality. Accessed 10 Feb. 2023.
Summarised by Radhika Jain
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