Commentary: Hot research on roasted lizards: warming, evolution and extinction in climate change studies

Abstract

news and update Putterman, L. (2008). Agriculture, diffusion and devel- opment: Ripple effects of the Neolithic Revolu- tion. Economica, 75, 729-748. Smith, A. (1776). An Inquiry into the Nature and Causes of the Wealth of Nations. Reprinted in 1976. University of Chicago Press, Chicago. William R. Burnside University of New Mexico, Albuquerque, NM, USA e-mail: burnsidewr@gmail.com http://biology.unm.edu/jhbrown/ labmembers.shtml Edited by Joaquin Hortal commentary Hot research on roasted lizards: warming, evolution and extinc- tion in climate change studies In volume 328 of Science, a team headed by Barry Sinervo published a study forecasting the effect of increased temperature in lizards. They demon- strate that climate change has already caused ex- tinctions of lizard populations worldwide. They also forecast that if climate change scenarios come true, 40% of all lizard populations and 20% of all species could be committed to extinction by 2080. Predictions are supported by a model that represents how much activity time will be re- stricted (i.e., hours of restriction; hr) because op- erative temperatures are too high. The study uses a multidisciplinary approach incorporating ecophysiology, evolutionary biology, biogeography and phylogenetics. A special strength of the study is that it uses models that are validated with data from recent population extinctions, which is an extremely rare feature in studies assessing climate change effects on biodi- versity (but see Araujo et al. 2005). Sinervo et al.’s study links temperature increases to the organis- mal biology of the lizards making it possible to predict local extinctions. Unfortunately, such a link leads to a worrisome message: “Climate- forced reptile extinctions are happening now” (Huey et al. 2010). Forecasts of species extinctions due to cli- mate change are typically based on assessments of changes in climatic suitability for species (e.g. Thomas et al. 2004; Thuiller et al. 2005). Sinervo and colleagues go beyond this climate envelope approach and incorporate aspects of the ecology and behavior that are thought to mediate the re- sponses of species to climate change. The incorpo- ration of ecological and behavioral mechanisms into models attempting to provide insight of the likely responses of species to climate change is welcomed (Brook et al. 2009), but when such at- tempts involve large numbers of species and bio- geographical scales compromises between preci- sion and generality are inevitable. One of such compromises is related to the use of estimated operative temperatures (the equilibrium temperature of a lizard with its ther- mal environment) in the study. Operative tem- peratures can vary greatly due to micro- environmental heterogeneity (Bauwens et al., 1996). Lizards may select locations with cooler micro-climates instead of moving higher in alti- tude or latitude. Open habitat species for exam- ple, may encroach into forests (Huey et al. 2009). This study would have benefited from integrating small scale thermal heterogeneity into large scale studies, although precisely how this can be ac- complished remains a key challenge for mechanis- tically motivated models of climate change. Investigators such as Kearney et al. (2008) and Mitchell et al. (2008) have created biophysical models of the thermal environment of reptiles to make predictions on the effect of global warming on individual species. These models use heat and energy balance equations to relate environmental conditions with ecophysiological traits measured in the laboratory. These relationships can be mapped geographically to evaluate climate suit- ability for the species of interest. Sinervo et al. frontiers of biogeography 2.3, 2010 — © 2010 the authors; journal compilation © 2010 The International Biogeography Society