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Widespread species often possess physiological mechanisms for coping with
thermal heterogeneity, and uncovering these mechanisms provides insight
into species responses to climate change. The emergence of non-invasive
corticosterone (CORT) assays allows us to rapidly assess physiological
responses to environmental change on a large scale. We lack, however, a
basic understanding of how temperature affects CORT, and whether
temperature and CORT interactively affect performance. Here, we examine
the effects of elevated temperature on CORT and whole-organism performance
in a terrestrial salamander, Plethodon cinereus, across a latitudinal
gradient. Using water-borne hormone assays, we found that raising ambient
temperature from 15 to 25&[deg]C increased CORT release at a
similar rate for salamanders from all sites. However, CORT release rate
was higher overall in the warmest, southernmost site. Elevated
temperatures also affected physiological performance, but the effects
differed among sites. Ingestion rate increased in salamanders from the
warmer sites but remained the same for those from cooler sites. Mass gain
was reduced for most individuals, though this reduction was more dramatic
in salamanders from the cooler sites. We also found a
temperature-dependent relationship between CORT and food conversion
efficiency (i.e., the amount of mass gained per unit food ingested). CORT
was negatively related to food conversion efficiency at 25&[deg]C
but was unrelated at 15&[deg]C. Thus, the energetic gains of
elevated ingestion rates may be counteracted by elevated CORT release
rates experienced by salamanders in warmer environments. By integrating
multiple physiological metrics, we highlight the complex relationships
between temperature and individual responses to warming climates.
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