Indirect Genetic Effects: A Cross-disciplinary Perspective on Empirical Studies

Abstract

Indirect genetic effects (IGE) occur when an individual's phenotype is influenced by genetic variation in conspecifics. Opportunities for IGE are ubiquitous, and, when present, IGE have profound implications for behavioral, evolutionary, agricultural, and biomedical genetics. Despite their importance, the empirical study of IGE lags behind the development of theory. In large part, this lag can be attributed to the fact that measuring IGE, and deconvoluting them from the direct genetic effects of an individual's own genotype, is subject to many potential pitfalls. In this Perspective, we describe current challenges that empiricists across all disciplines will encounter in measuring and understanding IGE. Using ideas and examples spanning evolutionary, agricultural, and biomedical genetics, we also describe potential solutions to these challenges, focusing on opportunities provided by recent advances in genomic, monitoring, and phenotyping technologies. We hope that this cross-disciplinary assessment will advance the goal of understanding the pervasive effects of conspecific interactions in biology.

Keywords: dynastic effect; genetic nurture; indirect genetic effect; interacting phenotypes; neighbor effect; social genetic effect.

Figure 2.1.

Example of correlation between focal environment and partner genotype.

Figure 2.2.

Example of correlation between partner environment and partner genotype.

Figure 2.3.

Example of correlation between direct and social genotypes.

Figure 2.4.

Example of shared environmental effects in the presence of a positive correlation between DGE and IGE.

Figure 2.5.

Theoretical illustration of a spurious association arising from the genoytpic correlation with a causal locus in an IGE mapping study.

Figure 2.6.

Greater sampling variance of the correlation between direct and social genotypes when each individual in the sample is used as both focal individual and social partner.