Impacts of climate warming on terrestrial ectotherms across latitude

Abstract

The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.biodiversity ͉ fitness ͉ global warming ͉ physiology ͉ tropical G lobal warming in this century may be the largest anthropogenic disturbance ever placed on natural systems (1, 2). Its impact on species is likely to vary geographically (2-4), but a mechanistic framework to predict its magnitude and global distribution has not yet been developed (5). One important determinant of biological responses to climate change will be the degree of warming itself, which will continue to be greater at high latitudes (6). Also relevant, however, is the physiological sensitivity of organisms to changes in the temperature of their environment (7,8). The thermal tolerance of many organisms has been shown to be proportional to the magnitude of temperature variation they experience (9-11), a characteristic of climate that also increases with latitude. Evaluating the impacts of rapidly changing climates on population fitness and survival thus requires linking geographic patterns of the magnitude of temperature change with the physiological sensitivity of organisms to that change (12).Ectotherms constitute the vast majority of terrestrial biodiversity (13) and are especially likely to be vulnerable to climate warming because their basic physiological functions such as locomotion, growth, and reproduction are strongly influenced by environmental temperature. The ability of ectotherms to perform such functions at different temperatures is described by a thermal performance curve (14), which rises gradually with temperature from a minimum critical temperature, CT min , to an optimum temperature, T opt , and then drops rapidly to a critical thermal maxi...

Host‐mediated shift in the cold tolerance of an invasive insect

“…However, these tools currently treat invading species as “homogenous and immutable entities” (Lee, 2002), being particularly void of adaptive parameters and plant–insect interactions. Climate change is exerting a powerful influence on the distributions of insects (Deutsch et al., 2008; Huey et al., 2012) and plants (Chown et al., 2012; Kelly & Goulden, 2008) and will continue to. Accurately forecasting the impacts of a changing climate on pest species demands a clear understanding of what drives their current temperature tolerances and especially their adaptive capacities.…”

The sea urchin Lytechinus variegatus lives close to the upper thermal limit for early development in a tropical lagoon

“…This suggests that their thermal safety margins (i.e., the difference between the UTL and environmental temperature) are smaller and therefore tropical species are under a greater risk from climate change than their temperate counterparts (Huey 1978; Deutsch et al. 2008; Clusella‐Trullas et al. 2011; Sunday et al.…”

Effect of warming rate on the critical thermal maxima of crabs, shrimp and fish

“…It has also been applied in macrophysiological comparative studies in ectotherms (e.g. Lee and Boulding, 2010;Cowles and Bogert, 1944;Lutterschmidt and Hutchison, 1997) and in the exploration of upper thermal tolerances across different taxa (Somero, 2005(Somero, , 2010Deutsch et al, 2008).…”