Abstract
Rainbow trout is farmed globally under diverse uncontrollable environments. Fish with low macroenvironmental sensitivity (ES) of growth is important to thrive and grow under these uncontrollable environments. The ES may evolve as a correlated response to selection for growth in one environment when the genetic correlation between ES and growth is nonzero. The aims of this study were to quantify additive genetic variance for ES of body weight (BW), defined as the slope of reaction norm across breeding environment (BE) and production environment (PE), and to estimate the genetic correlation (r g(int, sl)) between BW and ES. To estimate heritable variance of ES, the coheritability of ES was derived using selection index theory. The BW records from 43,040 rainbow trout performing either in freshwater or seawater were analysed using a reaction norm model. High additive genetic variance for ES (9584) was observed, inferring that genetic changes in ES can be expected. The coheritability for ES was either -0.06 (intercept at PE) or -0.08 (intercept at BE), suggesting that BW observation in either PE or BE results in low accuracy of selection for ES. Yet, the r g(int, sl) was negative (-0.41 to -0.33) indicating that selection for BW in one environment is expected to result in more sensitive fish. To avoid an increase of ES while selecting for BW, it is possible to have equal genetic gain in BW in both environments so that ES is maintained stable.
Highlights
The performance of organisms is influenced by the surrounding environmental conditions, leading to phenotypically plastic responses to environmental changes
In the Finnish data, GxE of body weight (BW) existed in both forms; re-ranking as indicating by rg of BW between breeding environment (BE) and production environment (PE) was 0.73, and heterogeneity of genetic variances (Table 2)
The additive genetic variance of slope of BW (9584) was considerable and the h2int was moderate in both environments (0.23 for PE and 0.25 for BE), the h2ES was low (0.07) implying the additive genetic variance of ES explains only a small proportion relative to total phenotypic variance of BW across environments
Summary
The performance of organisms is influenced by the surrounding environmental conditions, leading to phenotypically plastic responses to environmental changes. Such plastic responses have been observed, for example, as adaptive plasticity in the neck teeth of Daphnia (water fleas) which develops as a protective response to the chemical cues of a predatory Chaoborus present in the water [1]. Phenotypic plasticity has been explored especially from ecological and evolutionary points of view. There is evidence for genetic basis of phenotypic plasticity, for example in salmonids [2], Trinidadian guppies (Poecilia reticulata) [3,4] and pupfishes (Cyprinodon nevadensis) [5].
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