Mothers and not genes determine inherited differences in cadmium sensitivities within unexposed populations of the freshwater crustacean Gammarus fossarum

Abstract

Deciphering evolutionary processes occurring within contaminated populations is important for the ecological risk assessment of toxic chemicals. Whereas increased tolerance to contaminants is well documented in aquatic animal populations, whether such phenotypic changes occur through genetic adaptation is still debated. In that sense, several studies with the freshwater crustacean Gammarus concluded in a weak potential for genetic adaptation to cadmium (Cd), while others reported inheritable increased tolerance in Cd‐contaminated populations. Using quantitative genetics and selection experiments, this study sought to further assess the potential of Gammarus populations to genetically adapt to Cd. By combining the control of the reproductive cycle of this species in the laboratory and protocols of individual Cd exposure, we conducted half‐sib analyses to establish the genetic and environmental sources of variance in Cd sensitivity of neonates. Prior to experiments, computations allowed optimizing the experimental design in order to increase the power to detect additive genetic variance. The main findings are the existence of strong between‐brood variability along with weak heritability of Cd sensitivity within Gammarus populations. This study also revealed a significant maternal effect on individual Cd sensitivity. This sheds new light on the importance of maternal influence in microevolutionary processes occurring in contaminated environments.

Detecting Cd adaptation footprint in C. riparius with a multi-genomic approach

“…This particular scenario was designed to take into account the relevance of gradual directional environmental changes (Gorter et al, 2017), that can profoundly affect the course and outcome of evolution. Indeed, while consistent Cd tolerance can be observed on laboratory and field populations suddenly exposed to a constant high concentration of the metal (Chaumot et al, 2016;Pedrosa et al, 2017b;Postma and Davids, 1995;Ward and Robinson, 2005), Cd tolerance on populations exposed to sublethal concentrations is highly variable, occurring only in a small number of individuals and weakly heritable (Chaumot et al, 2016;Groenendijk et al, 2002;Marinković et al, 2012;Sheir et al, 2013).…”

Osmoregulatory responses to cadmium in reference and historically metal contaminated Gammarus fossarum (Crustacea, Amphipoda) populations

“…The HO profiles reported in the present study are in accordance with these previous results, and they confirm the high inter-individual variability of responses to Cd in this population. As variability due to sex, size/age and molt cycle was avoided by selecting only males of a determined size range and intermolt stage in both studies, the observed heterogeneity of HO values in responses to contamination may be due to a high genetic and/or phenotypic variability within and between populations (Vigneron et al, 2015(Vigneron et al, , 2016.…”