Abstract
Climate change is predicted to change the distribution and abundance of species, yet underlying physiological mechanisms are complex and methods for detecting populations at risk from rising temperature are poorly developed. There is increasing interest in using physiological mediators of the stress response as indicators of individual and population-level response to environmental stressors. Here, we use laboratory experiments to show that the temperature thresholds in brook trout (Salvelinus fontinalis) for increased gill heat shock protein-70 (20.7°C) and plasma glucose (21.2°C) are similar to their proposed thermal ecological limit of 21.0°C. Field assays demonstrated increased plasma glucose, cortisol and heat shock protein-70 concentrations at field sites where mean daily temperature exceeded 21.0°C. Furthermore, population densities of brook trout were lowest at field sites where temperatures were warm enough to induce a stress response, and a co-occurring species with a higher thermal tolerance showed no evidence of physiological stress at a warm site. The congruence of stress responses and proposed thermal limits supports the use of these thresholds in models of changes in trout distribution under climate change scenarios and suggests that the induction of the stress response by elevated temperature may play a key role in driving the distribution of species.
Highlights
Environmental temperature exerts a primary constraint on the distribution and abundance of species
There was no significant relationship between temperature and plasma cortisol (Fig. 1c; P = 0.43), whereas plasma glucose increased with temperature (Fig. 1d; piecewise linear regression, P = 0.01, r2 = 0.96), with a threshold for induction of 21.2°C
We used laboratory experiments to demonstrate the induction of endocrine and cellular stress responses by elevated temperature in brook trout
Summary
Environmental temperature exerts a primary constraint on the distribution and abundance of species. With predicted global increases in temperature, there is concern over the future of species whose appropriate thermal habitats will shift and shrink. A number of studies have documented poleward and elevational shifts in species ranges across a variety of taxa (Parmesan and Yohe, 2003; Root et al, 2003). Models based on the current relationships between distribution and temperature have been used to estimate the change in species’ ranges under climate change scenarios. Uncertainty concerning species’ thermal thresholds and the presence of multiple limiting factors may reduce confidence in these predictions. This work is written by (a) US Government employee(s) and is in the public domain in the US
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