Transgenerational plasticity and the capacity to adapt to low salinity in the eastern oyster, Crassostrea virginica.

Joanna S Griffiths,Kyle A Sirovy,Morgan W Kelly,Kevin M Johnson,Jerome F La Peyre,Mark S Yeats,Francis T C Pan

doi:10.1098/rspb.2020.3118

Abstract

Salinity conditions in oyster breeding grounds in the Gulf of Mexico are expected to drastically change due to increased precipitation from climate change and anthropogenic changes to local hydrology. We determined the capacity of the eastern oyster, Crassostrea virginica, to adapt via standing genetic variation or acclimate through transgenerational plasticity (TGP). We outplanted oysters to either a low- or medium-salinity site in Louisiana for 2 years. We then crossed adult parents using a North Carolina II breeding design, and measured body size and survival of larvae 5 dpf raised under low or ambient salinity. We found that TGP is unlikely to significantly contribute to low-salinity tolerance since we did not observe increased growth or survival in offspring reared in low salinity when their parents were also acclimated at a low-salinity site. However, we detected genetic variation for body size, with an estimated heritability of 0.68 ± 0.25 (95% CI). This suggests there is ample genetic variation for this trait to evolve, and that evolutionary adaptation is a possible mechanism through which oysters will persist with future declines in salinity. The results of this experiment provide valuable insights into successfully breeding low-salinity tolerance in this commercially important species.

Highlights

Our rapidly changing climate will expose organisms to novel and potentially stressful environments
To evaluate the capacity for adaptation to changing environments, we explore the influence of genetic variation and transgenerational plasticity (TGP) on larval growth rates in the eastern oyster, Crassostrea virginica, an ecologically and economically important species in the northern Gulf of Mexico
We investigated the influence of the environment, TGP and additive genetic variation on fitness-related traits in C. virginica exposed to stressful low salinities

Summary

Introduction

Our rapidly changing climate will expose organisms to novel and potentially stressful environments. The interplay of intra-generational and TGP and evolution needs further investigation to accurately predict a species’ response to climate change [27] These mechanisms may work in tandem, whereby plasticity prevents a population from going extinct by extending the time over which selection has the opportunity to act [28]. We investigated the influence of the environment, TGP and additive genetic variation on fitness-related traits in C. virginica exposed to stressful low salinities. We first investigated the effects of the parental environment by rearing hatchery-bred oysters at either a low- or mediumsalinity field site for 2 years (figure 1a) and measuring growth and mortality to characterize fitness and overall stress. We quantified the presence of additive genetic variation for larval body size when reared at either low or ambient salinity to determine the population’s capacity to adapt to future changes in salinity

Methods

Results

Findings

Discussion

Conclusion and future implications