Abstract
AbstractAimWarmer temperatures directly increase metabolic rates of ectotherms, but temperature also indirectly affects metabolic rates. Higher temperatures result in smaller body sizes and associated decreases in metabolic rates, and it remains unknown whether this indirect effect of temperature increase could mitigate the direct positive effect of temperature on metabolic rate. Here, we assess whether temperatureâinduced shifts in body size are likely to offset the direct influence of temperature on metabolic rate.LocationGlobal.Time period1940â2011.Major taxa studiedEctotherms.MethodsWe compiled literatureâderived data on mass and temperature for 109 ectotherm species raised at various constant temperatures. Using an allometric equation to estimate metabolic rate from size and temperature, we determined the body masses necessary for species to maintain constant metabolic rates under increased temperatures. We also calculated and compared (a) change in metabolic rate attributable to increased temperature where body size does not change with (b) change in metabolic rate including empirical size change.ResultsWarmer temperatures resulted in increased metabolic rate estimates, but this was partly offset by decreased body sizes for the majority of species. For most species, observed decreases in body size at higher temperatures were insufficient to avoid metabolic rate increases.Main conclusionsAlthough the indirect effect of temperature on metabolic rate via body size is not sufficient to counterbalance the direct effect, it limits the magnitude of the increase in metabolic rate. Thus, in a warming climate, ectotherms are likely to experience increases in energy use that are smaller than anticipated. Given that metabolic rates have substantial, diverse impacts on individuals, populations, and ecosystems, these indirect effects of temperature change will have complex cascading effects on ecological communities, but the impacts of increases in metabolic rate of these varying magnitudes are unknown.
Highlights
Environmental temperature influences organisms in many ways; it can increase or decrease rates of physiological processes (Brown et al, 2012), determine timing of reproduction (Olive, 1995), or even directly affect mortality (Pauly, 1980)
Warmer temperatures resulted in increased metabolic rate estimates, but this was partially offset by decreased body sizes for the majority of species
Main conclusions While the indirect effect of temperature on metabolic rate via body size is not sufficient to counterbalance the direct effect, it limits the magnitude of metabolic rate increase
Summary
Environmental temperature influences organisms in many ways; it can increase or decrease rates of physiological processes (Brown et al, 2012), determine timing of reproduction (Olive, 1995), or even directly affect mortality (Pauly, 1980). Because of the far-reaching influence of temperature, projected increases due to climate change are expected to substantially alter diverse species characteristics. Environmental temperature directly influences metabolic rates through its influence on the rate of biological reactions that underlie metabolism. Changes in metabolic rate affect many aspects of organismal biology and ecology, including individual fitness (Burton et al, 2011), population dynamics (Buckley et al, 2014), community composition (Marquet et al, 2004), and ecosystem processes such as ecosystem respiration and nutrient cycling
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