Tolerance traits related to climate change resilience are independent and polygenic. (1st August 2018) - Healy, Timothy M.
Abstract: The resilience of organisms to climate change through adaptive evolution is dependent on the extent of genetically based variation in key phenotypic traits and the nature of genetic associations between them. For aquatic animals, upper thermal tolerance and hypoxia tolerance are likely to be a important determinants of sensitivity to climate change. To determine the genetic basis of these traits and to detect associations between them, we compared naturally occurring populations of two subspecies of Atlantic killifish, Fundulus heteroclitus, that differ in both thermal and hypoxia tolerance. Multilocus association mapping demonstrated that 47 and 35 single nucleotide polymorphisms (SNPs) explained 43.4% and 51.9% of variation in thermal and hypoxia tolerance, respectively, suggesting that genetic mechanisms underlie a substantial proportion of variation in each trait. However, no explanatory SNPs were shared between traits, and upper thermal tolerance varied approximately linearly with latitude, whereas hypoxia tolerance exhibited a steep phenotypic break across the contact zone between the subspecies. These results suggest that upper thermal tolerance and hypoxia tolerance are neither phenotypically correlated nor genetically associated, and thus that rates of adaptive change in these traits can be independently fine‐tuned by natural selection. This modularity of important traits can underpin the evolvability of organisms to complex future environmental change. Abstract : For aquatic organisms, variation in the ability to tolerate high temperatures and low oxygen levels is likely to influence resilience to climate change. Here, we use populations of killifish to show that naturally occurring variations in upper thermal tolerance and hypoxia tolerance have genetic bases, and that these two traits are not functionally or genetically correlated. This genetic variation provides the material needed for the action of natural selection, but the lack of trait association could limit rapid adaptation to combined stressors. However, this lack of association potentially provides flexibility to fine‐tune adaptive responses to specific local conditions.