The Origin of Additive Genetic Variance Driven by Positive Selection. (3rd April 2020)

• Record Type: Journal Article
• Authors: Liu, Li; Wang, Yayu; Zhang, Di; Chen, Zhuoxin; Chen, Xiaoshu; Su, Zhijian; He, Xionglei
• Editors: Zhang, Jianzhi
• Is Part Of: Molecular biology and evolution. Volume 37:Number 8(2020)
• Page Start: 2300
• Page End: 2308
• Publication Date: 2020-04-03
• Subjects: adaptive divergence -- population admixture -- complex trait -- additive variance -- Fisher's theorem of natural selection -- positive selection; Molecular biology -- Periodicals; Molecular evolution -- Periodicals; Evolution, Molecular -- Periodicals; Molecular Biology -- Periodicals; 572.8
• DOI: 10.1093/molbev/msaa085
• Languages: English
• ISSNs: 0737-4038

Abstract

Abstract: Fisher's fundamental theorem of natural selection predicts no additive variance of fitness in a natural population. Consistently, studies in a variety of wild populations show virtually no narrow-sense heritability ( h 2 ) for traits important to fitness. However, counterexamples are occasionally reported, calling for a deeper understanding on the evolution of additive variance. In this study, we propose adaptive divergence followed by population admixture as a source of the additive genetic variance of evolutionarily important traits. We experimentally tested the hypothesis by examining a panel of ∼1, 000 yeast segregants produced by a hybrid of two yeast strains that experienced adaptive divergence. We measured >400 yeast cell morphological traits and found a strong positive correlation between h 2 and evolutionary importance. Because adaptive divergence followed by population admixture could happen constantly, particularly in species with wide geographic distribution and strong migratory capacity (e.g., humans), the finding reconciles the observation of abundant additive variances in evolutionarily important traits with Fisher's fundamental theorem of natural selection. Importantly, the revealed role of positive selection in promoting rather than depleting additive variance suggests a simple explanation for why additive genetic variance can be dominant in a population despite the ubiquitous between-gene epistasis observed in functional assays.