Abstract
Understanding how populations adapt to different thermal environments is an important issue for biodiversity conservation in the context of recent global warming. To test the hypothesis that populations from southern region are more sensitive to climate change than northern region in cold-water species, we determined the thermal tolerance of two geographical populations of a cold-water fish, Rhynchocypris oxycephalus: the Hangzhou population from southern region and the Gaizhou population from northern region, then compared their transcriptomic responses between a control and a high temperature treatment. The results showed that the thermal tolerance range and thermal tolerance polygon area of Hangzhou population were narrower than the Gaizhou population, indicating populations from southern region were possibly more vulnerable. Further transcriptomic analysis revealed that the Gaizhou population expressed more temperature responding genes than the Hangzhou population (583 VS. 484), corresponding with their higher thermal tolerance, while some of these genes (e.g. heat shock protein) showed higher expression in the Hangzhou population under control condition, suggesting individuals from southern region possibly have already responded to the present higher environmental temperature pressure. Therefore, these results confirm the prediction that populations from southern region are more sensitive to global warming, and will be important for their future conservation.
Highlights
Thermal adaptation is one of the most important factors that influence the fates of species in response to recent global warming[1,2]
Mechanisms of temperature adaptations were examined by comparing thermal tolerance and transcriptomic responses to high temperature between two geographical populations in a cold-water species R. oxycephalus
The results demonstrated that the southern population (Hangzhou) has narrower thermal tolerance range than the northern population (Gaizhou), suggesting populations from southern regions are more heat sensitive to high temperature
Summary
Thermal adaptation is one of the most important factors that influence the fates of species in response to recent global warming[1,2]. The northern population of Australian barramundi exhibited higher tolerance to high temperatures than the southern one, and the northern population expressed 521 DEGs following heat stress while the southern one had only 171 genes[25]. Another transcriptomic study on populations of redband trout (Oncorhynchus mykiss gairdneri, cold-water species) revealed fish from the hot-adapted population (desert strain) had more DEGs than those from the cool-adapted population (montane strain) under thermal stress[33]. As a broadly distributed species with a complex phylogeographic history, these geographically distinct populations have persisted long time to cope with and adapt to the different thermal environments, which can work as an indicator species to study the intraspecific variation in thermal tolerance and the underlying molecular mechanisms in resistance to different environmental challenges
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