A global heterothermic continuum in mammals. Issue 9 (4th June 2013)

• Record Type: Journal Article
• Authors: Boyles, Justin G.; Thompson, Amy B.; McKechnie, Andrew E.; Malan, Ezit; Humphries, Murray M.; Careau, Vincent
• Is Part Of: Global ecology & biogeography. Volume 22:Issue 9(2013:Sep.)
• Page Start: 1029
• Page End: 1039
• Publication Date: 2013-06-04
• Subjects: Ecology -- Periodicals; Biogeography -- Periodicals; Biodiversity -- Periodicals; Macroevolution -- Periodicals; 577
• DOI: 10.1111/geb.12077
• Languages: English
• ISSNs: 1466-822X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <sec id="geb12077-sec-0001" sec-type="section"> <title>Aim</title> <p>The ability of endotherms to physiologically regulate body temperature (T<sub>b</sub>) is presumed to be important in the adaptive radiation of birds and mammals. Recently, attention has shifted towards determining the extent and energetic significance of T<sub>b</sub> variation documented in an ever‐expanding list of species. Thus, we provide the first global synthesis of ecological and evolutionary correlates of variation in mammalian T<sub>b</sub>.</p> </sec> <sec id="geb12077-sec-0002" sec-type="section"> <title>Location</title> <p>World‐wide</p> </sec> <sec id="geb12077-sec-0003" sec-type="section"> <title>Methods</title> <p>We conducted a phylogenetically informed analysis of T<sub>b</sub> variation using two complementary metrics, namely Thermoregulatory Scope (TS) and Heterothermy Index (HI), that treat T<sub>b</sub> variation as a continuous variable. We included morphological (e.g. body mass), ecological (e.g. food habits) and environmental (e.g. latitude) correlates in the analysis.</p> </sec> <sec id="geb12077-sec-0004" sec-type="section"> <title>Results</title> <p>Among 560 mammal species included in the TS analysis, T<sub>b</sub> relates most strongly to body mass (included in all models), season (relative parameter weight: 0.95), absolute latitude (0.80) and hoarding behavior (0.72), with small‐bodied, high latitude and non‐hoarding species expressing the most T<sub>b</sub> variation. Small‐bodied and high latitude species also express a greater range of thermoregulatory patterns than large‐bodied and low latitude species. Results were generally similar in HI analysis, but in summer the extent of heterothermy decreases with latitude.</p> </sec> <sec id="geb12077-sec-0005" sec-type="section"> <title>Main conclusions</title> <p>Mammalian heterothermy is related to evolutionary history, climate conditions constraining minimum T<sub>b</sub>, resource conditions mediating energy supply for maintaining high T<sub>b</sub>, and latitudinal variation in the nature of seasonality. Our analysis further shows that traditional classification of mammals as hibernators, daily heterotherms or homeotherms is clouded or possibly misleading.</p> </sec> </abstract>