The early-life environment of a pig shapes the phenotypes of its social partners in adulthood

Abstract

Social interactions among individuals are abundant, both in natural and domestic populations, and may affect phenotypes of individuals. Recent research has demonstrated that the social effect of an individual on the phenotype of its social partners may have a genetic component, known as an indirect genetic effect (IGE). Little is known, however, of nongenetic factors underlying such social effects. Early-life environments often have large effects on phenotypes of the individuals themselves later in life. Offspring development in many mammalian species, for example, depends on interactions with the mother and siblings. In domestic pigs, individuals sharing the same juvenile environment develop similar body weight later in life. We, therefore, hypothesized that offspring originating from the same early-life environment also develop common social skills that generate early-life social effects (ELSEs) that affect the phenotypes of their social partners later in life. We, therefore, quantified IGEs and ELSEs on growth in domestic pigs. Results show that individuals from the same early-life environment express similar social effects on the growth of their social partners, and that such ELSEs shape the growth rate of social partners more than IGEs. Thus, the social skills that individuals develop in early life have a long-lasting impact on the phenotypes of social partners. Early-life and genetic social effects were independent of the corresponding direct effects of offspring on their own growth, indicating that individuals may enhance the growth of their social partners without a personal cost. Our findings also illustrate how research devoted to quantifying IGEs may miss nongenetic and potentially confounded social mechanisms which may bias the estimates of IGEs.

The predictive ability of indirect genetic models is reduced when culled animals are omitted from the data

“…familiarity. Information on early-life experience may allow these effects to be disentangled [38], but such information was not available in our study.…”

The Social Genome of Friends and Schoolmates in the National Longitudinal Study of Adolescent to Adult Health

“…Social-genetic effects, also called "indirect" genetic effects, refer to the influence of one organism's genotype on a different organism's phenotype (14,15). Social-genetic effects, which may take several forms (1), are accounted for in evolutionary theory (42,43) and have been observed among animals (15,(44)(45)(46)(47) and received some study in human siblings (14,48,49).…”

Increased developmental density decreases the magnitude of indirect genetic effects expressed during agonistic interactions in an insect

“…; Canario et al. ). Indeed, IGEs can greatly influence evolutionary trajectories because they change the proportion of heritable variation on which selection can act (Bijma et al.…”

“…In animals, IGEs have been documented for a large number of phenotypic traits, including aggressiveness (Wilson et al 2009;Saltz 2013;Alemu et al 2014;Santostefano et al 2017), dominance (Moore et al 2002;Wilson et al 2011), parental care (Hunt and Simmons 2002;Head et al 2012;Ashbrook et al 2015), cooperation (Linksvayer 2006), sexual behavior (Petfield et al 2005 Marie-Orleach et al 2017), and timing of reproduction (Brommer and Rattiste 2008;Germain et al 2016). In plants and fungi, the role of IGEs has also been recognized in research focusing on the role of competition in growth and reproduction (Mutic and Wolf 2007;Wolf et al 2011;Costa e Silva et al 2013;Costa e Silva et al 2017;Rode et al 2017), while a key role of IGEs in trait evolution is widely recognized in evolutionary research on commercial livestock aimed at decreasing the adverse effects of competition (Camerlink et al 2013;Camerlink et al 2015;Ellen et al 2016;Canario et al 2017). Indeed, IGEs can greatly influence evolutionary trajectories because they change the proportion of heritable variation on which selection can act (Bijma et al 2007;Bijma and Wade 2008;Bijma 2011;Bijma 2014;Wilson 2014).…”