Genomic heritability estimation for the early life-history transition related to propensity to migrate in wild rainbow and steelhead trout populations.

Guo Hu,Chunkao Wang,Yang Da

doi:10.1002/ece3.1038

Abstract

A previous genomewide association study (GWAS) identified SNP markers associated with propensity to migrate of rainbow and steelhead trout (Oncorhynchus mykiss) in a connected population with free access to the ocean in Upper Yakima River (UYR) and a population in Upper Mann Creek (UMC) that has been sequestered from its access to the ocean for more than 50 years. Applying genomic heritability estimation using the same dataset, we found that smoltification in the UYR population were almost completely determined by additive effects, with 95.5% additive heritability and 4.5% dominance heritability, whereas smoltification in the UMC population had substantial dominance effects, with 0% additive heritability and 39.3% dominance heritability. Dominance test detected one SNP marker (R30393) with significant dominance effect on smoltification (P = 1.98 × 10−7). Genomic-predicted additive effects completely separated migratory and nonmigratory fish in the UYR population, whereas genomic-predicted dominance effects achieved such complete separation in the UMC population. The UMC population had higher genomic additive and dominance correlations than the UYR population, and fish between these two populations had the least genomic correlations. These results suggested that blocking the free access to the ocean may have reduced genetic diversity and increased genomic similarity associated with the early life-history transition related to propensity to migrate.

Highlights

Anadromy is a complex type of life cycle history found among several fish species including lampreys, sturgeons, basses, and salmonids (Dingle 1991; Stefansson et al 2008)
For the SMOLT phenotypic values on the original observed scale using the mixed model with additive effect only by deleting dominance effect from Equation (1), both GVCBLUP and GCTA had genomic-additive heritability estimates of h2ao = 1.00 in the Upper Yakima River (UYR) population and h2ao = 0.00 in the Upper Mann Creek (UMC) population
In the UMC population, h2a = 0, h2d = H2 = 0.393. These results indicated that SMOLT in the UMC population had substantial dominance effects but additive or allelic effects were either lost or inactive possibly due to the 50 years of dam blocking to fish migration

Summary

Introduction

Anadromy is a complex type of life cycle history found among several fish species including lampreys, sturgeons, basses, and salmonids (Dingle 1991; Stefansson et al 2008). Steelhead and rainbow trout occur in sympatry throughout the species range in rivers and lakes with access to the sea (Behnke 2002), and either type of O. mykiss could be derived from one another (Zimmerman and Reeves 2000; Pascual et al 2002; Thrower et al 2004a). After a period of juvenile growth, steelhead trout reared in freshwater will undergo a complex early life-history transformation related to the propensity to migrate (smoltification) to the sea. Smoltification is a unique feature of salmonid anadromy and involves a number of developmental changes in the biochemistry, physiology,

Methods

Results

Conclusion