Abstract
Defining ecologically relevant upper temperature limits of species is important in the context of environmental change. The approach used in the present paper estimates the relationship between rates of temperature change and upper temperature limits for survival in order to evaluate the maximum long-term survival temperature (Ts). This new approach integrates both the exposure time and the exposure temperature in the evaluation of temperature limits. Using data previously published for different temperate and Antarctic marine environments, we calculated Ts in each environment, which allowed us to calculate a new index: the Warming Allowance (WA). This index is defined as the maximum environmental temperature increase which an ectotherm in a given environment can tolerate, possibly with a decrease in performance but without endangering survival over seasonal or lifetime time-scales. It is calculated as the difference between maximum long-term survival temperature (Ts) and mean maximum habitat temperature. It provides a measure of how close a species, assemblage or fauna are living to their temperature limits for long-term survival and hence their vulnerability to environmental warming. In contrast to data for terrestrial environments showing that warming tolerance increases with latitude, results here for marine environments show a less clear pattern as the smallest WA value was for the Peru upwelling system. The method applied here, relating upper temperature limits to rate of experimental warming, has potential for wide application in the identification of faunas with little capacity to survive environmental warming.
Highlights
Understanding the factors shaping variation in the physiology, ecology, and evolution of organisms is a fundamental issue for biologists [1,2,3,4,5]
For the overall approach comparing different temperate regions, the literature review focused on papers providing data on upper temperature limits and matching different criteria: i) marine subtidal species in temperate environments, ii) experiments conducted during the summer season and iii) experiments using preacclimation were included only if they were done at the corresponding in situ temperature
Two types of experiments were taken into account: i) those that used the dynamic method in which the temperature is progressively increased until 50% of the individuals in the trial have died and ii) the static method in which the temperature is raised to a set value and the time at which 50% of the individuals have died is recorded [14]
Summary
Understanding the factors shaping variation in the physiology, ecology, and evolution of organisms is a fundamental issue for biologists [1,2,3,4,5]. Among environmental parameters temperature is possibly the best characterised and most fundamental as it affects the rates of all biochemical reactions; it drives species distribution and ecosystem level responses to climate variability [6,7]. Two main approaches currently dominate the investigation of likely responses of organism distributions to this change. The second is based around experiments where animals are held in the laboratory or modified field situations and conditions are manipulated [11,12,13]. Data from the latter will be utilised in this analysis
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