Abstract:
Changes in body temperature affect all aspects of an organism’s physiology (function) including metabolic rate, ability to obtain oxygen, and capacities for movement, reproduction and growth. Therefore, climate change—global warming—poses serious threats to ectothermic species, those organisms whose body temperatures change asenvironmental temperature rises or falls. Physiological studies have numerous contributions to make to our understanding of effects of climate change on individual species and entire ecosystems. Mechanistic analyses can identify physiological systems that set thermal optima and thermal tolerance limits and can elucidate how these optima and limits differ among species. Through this type of comparative physiological analysis it may be possible to make predictions about which species will succeed and which species will fail in a warming world, “winners” and “losers,” respectively. This lecture will focus on two ecosystems: rocky intertidal habitats where large changes in temperature are common, and cold, thermally stable waters of the Southern Ocean in Antarctica. Comparisons of congeneric species (species belonging to a common genus but adapted to different temperatures) of intertidal and subtidal marine ectotherms show that the most heat-adapted species may be threatened the most by further increases in habitat temperature, a seemingly paradoxical finding that also applies to terrestrial ectotherms. Antarctic marine ectotherms are especially threatened by warming because, during their long evolutionary histories at stable, cold temperatures near the freezing point of seawater, these species have lost numerous genes that are needed for function at higher temperatures, including genes for oxygen-transport proteins and for regulating the heat-shock response. These physiological studies thus suggest that both polar and tropical ecosystems are especially threatened by global warming.

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