The effects of supergene evolution on the structure and stability of the G-matrix

The G-matrix, a collection of additive genetic variances and covariances, reflects heritable variation within populations and is frequently employed to foresee the rate and direction of multivariate evolution over short periods. These (co)variances are influenced by pleiotropy and genetic linkage, phenomena often linked to supergenes created by chromosomal inversions. However, the impact of supergene evolution on the G-matrix's structure and temporal stability remains uncertain.

To examine this subject, researchers utilized mathematical analysis and individual-based simulations. These tools helped them explore the evolution and genetic ramifications of inversions that encompass numerous pleiotropic loci responsible for two traits influenced by disruptive and correlational selection (favouring specific trait value combinations).

The findings indicate that inversions evolve under disruptive selection and persist due to balancing selection because they maintain associations among alleles that create distinct phenotypic morphs. The genetic architecture mirrors the selection's impact on the traits: when selection encourages diversification along a joint trait combination, it generally generates a single multi-trait supergene.

Conversely, when selection promotes independent diversification of each trait, multiple inversions that can segregate independently are formed.

By hindering recombination, these inversions boost additive genetic variance and narrow-sense heritability, and stabilize the overall amount of additive genetic variation across time. When dominance is allowed to evolve, dominance relationships align across linked loci within supergenes. Although most genetic variance stays additive at the population level, the coordinated dominance relationships within supergenes contribute to the G-matrix's structure and stability.