Less competition leads to more uniformity

New quantitative genetic model

In the recent study published in Heredity, scientists of Wageningen University & Research and Swedish University of Agricultural Sciences present a new quantitative genetic model which integrates competition and variability and demonstrates co-evolution of the two phenomena. This model can be used for breeding programs in the near future to utilize genetic variation that was so far untapped.

Genetic basis between competition and variability

For years, animal breeders have been wondering if the relationship between competition and variability may have a genetic basis, i.e., if evolution of cooperation (less competition) leads to more uniformity (less variability). Until now, little progress has been made in this area of research, largely due to a lack of quantitative genetics models that connect the two phenomena.

Social interactions shape the world

Social interactions are present everywhere in the nature and they shaped the world we see today. These interactions may be positive, such as maternal care, or negative, for example competition. In animal breeding, competition for the resources affects health, welfare, and performance of the animals. In aquaculture populations, and some plants, competition also increases variability of trait values among individuals.

Inherited variability of traits

Variability of trait values has been studied as a quantitative trait in itself for decades, and it is often referred to as inherited variability. Inherited variability is relevant for both natural and domestic populations. In nature, variability of traits values affects phenotypic evolution, while in domestic populations, selection for uniform animals has an economic importance. Ample studies showed substantial potential for improvement of uniformity for many traits through selection. However, until now, inherited variability has been considered as a property of a single individual only, i.e., affected solely by individual’s own genes, also known as direct genetic effect.

Social genetic effect

Scientists from Wageningen University & Research and Swedish University of Agricultural Sciences showed that variability may have an additional genetic component, one that resides not within an animal itself, but within their social partners, a phenomenon known as “social genetic effect”. This is an important finding, as classical selection generally ignores social genetic effects, yet their impact on the potential of the trait to evolve may be large.

Implications of this research

Hence inheritance of phenotypic variability may differ from that of ordinary traits, as part of the genetic variation is “hidden” in the social partner. Improvement of uniformity will therefore require selection for both direct and social genetic effects. In a follow-up study, same group of scientists showed that it is possible to capture social genetic effects by using already available statistical models. These models would require information of animals’ phenotype, say body weight, and who they interacted with. This knowledge is generally obtained from group-structured data/experiments, but may also soon become available in a commercial setting due to development of phenotyping techniques that can track and record large numbers of individuals. Hence, application of the newly developed quantitative genetic model, and utilization of social genetic effects in breeding programs may become common practice in the near future.