The environmental genomics of metazoan thermal adaptation

Abstract

Continued and accelerating change in the thermal environment places an ever-greater priority on understanding how organisms are going to respond. The paradigm of ‘move, adapt or die', regarding ways in which organisms can respond to environmental stressors, stimulates intense efforts to predict the future of biodiversity. Assuming that extinction is an unpalatable outcome, researchers have focussed attention on how organisms can shift in their distribution to stay in the same thermal conditions or can stay in the same place by adapting to a changing thermal environment. How likely these respective outcomes might be depends on the answer to a fundamental evolutionary question, namely what genetic changes underpin adaptation to the thermal environment. The increasing access to and decreasing costs of next-generation sequencing (NGS) technologies, which can be applied to both model and non-model systems, provide a much-needed tool for understanding thermal adaptation. Here we consider broadly what is already known from non-NGS studies about thermal adaptation, then discuss the benefits and challenges of different NGS methodologies to add to this knowledge base. We then review published NGS genomics and transcriptomics studies of thermal adaptation to heat stress in metazoans and compare these results with previous non-NGS patterns. We conclude by summarising emerging patterns of genetic response and discussing future directions using these increasingly common techniques.

Thermal stress induces a distinct transcriptome profile in the Pacific oyster Crassostrea gigas

“…Also, oxidative stress with ROS accumulation can be accelerated by an increase in metabolism (e.g. protein metabolism, immune response) at higher temperatures (Winston and Digiulio, 1991;Porcelli et al, 2015). In the Pacific oyster, responses of antioxidant defence system upon heat-triggered oxidative stress are very complicated and differentially modulated by temperature gradients combined with exposure periods.…”

Thermal evolution offsets the elevated toxicity of a contaminant under warming: A resurrection study in Daphnia magna

“…This can be expected because when a population evolves tolerance to a certain stressor that environmental condition is no longer experienced as a stressor (Vam Straalen, 2003). With regard to warming, the acquisition of genetic adaptation to higher temperatures has been demonstrated in several taxa and has been linked to changes in gene expressions (e.g., Garvin, Thorgaard, & Narum, 2015; Gleason & Burton, 2015; Narum, Campbell, Meyer, Miller, & Hardy, 2013; Porcelli, Butlin, Gaston, Joly, & Snook, 2015; for the study species: Jansen et al., 2017; Yampolsky et al., 2014). Thermal evolution is expected to reduce the energetic costs of dealing with warming, thus leaving more energy to deal with stressors such as toxicants, thereby potentially offsetting the synergism between the toxicant and warming.…”

The importance of phenotypic plasticity and local adaptation in driving intraspecific variability in thermal niches of marine macrophytes

“…However, wild GWA studies are still subject to the confounding effects of phenotypic plasticity, as determining whether the phenotype being scored is due to plasticity or adaption remains challenging. This leads to issues with identifying thermal phenotypes (along a latitudinal gradient for instance) and may be a reason why, to date, no study has linked thermal phenotype to genotype in this way (Porcelli et al 2015).…”