Are we underestimating the ecological and evolutionary effects of warming? Interactions with other environmental drivers may increase species vulnerability to high temperatures

Abstract

Warming, the most prominent aspect of global environmental change, already affects most ecosystems on Earth. In recent years, biologists have increasingly integrated the effects of warming into their models by capturing how temperature shapes their physiology, ecology, behavior, evolutionary adaptation, and probability of extirpation/extinction. The more physiologically-grounded approaches to predicting ectotherms’ responses use thermal performance curves (TPCs) obtained by measuring species performance (e.g., growth rate) under different temperatures while other factors are held constant. These other factors are usually held at benign levels to ‘isolate’ the effects of temperature. Here we highlight that this practice may paint a misleading picture because TPCs are functions of other factors, including global change stressors. We review evidence that resource limitation, pH, oxygen and CO2 concentration, water availability, as well as parasites, all influence TPC shape and thermal traits such as optimum temperature for growth. Evidence from a wide variety of organisms – phytoplankton, protists, plants, insects, and fish – points towards such interactions increasing organisms’ susceptibility to high temperatures. Failing to account for these interactions is likely to lead to erroneous predictions of performance in nature and possibly an underestimation of the risks of warming. We discuss the general patterns and possible consequences of such interactions for ecological communities. But importantly, interactions with TPCs share common features that we can learn from. Incorporating these interactions into population and community models should lead to deeper insights and more accurate predictions of species’ performance in nature, now and in the future.

Predicting effects of multiple interacting global change drivers across trophic levels

“…Others have previously proposed reaction norms of vital rates as a starting point to merge physiology with multiple driver research (Collins et al, 2022; Harley et al, 2017; Litchman & Thomas, 2022; Pirotta et al, 2022). Litchman and Thomas (2022) reviewed the literature on phytoplankton growth and found that all reviewed global change drivers can influence the shape of the TPCs.…”

“…Others have previously proposed reaction norms of vital rates as a starting point to merge physiology with multiple driver research (Collins et al, 2022; Harley et al, 2017; Litchman & Thomas, 2022; Pirotta et al, 2022). Litchman and Thomas (2022) reviewed the literature on phytoplankton growth and found that all reviewed global change drivers can influence the shape of the TPCs. Collins et al (2022) then made the point that response curves for phytoplankton can only be produced with many driver levels, including unrealistic levels that are not expected to happen in nature.…”