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We tested the hypothesis that interspecific variation in chiropteran heat tolerance and evaporative cooling capacity is correlated with day-roost microclimates, using three vespertilionid bats that occur sympatrically during summer in Saskatchewan, Canada. We predicted that hoary bats (Lasiurus cinereus (Palisot de Beauvois, 1796); ~22 g) would have higher heat tolerance than little brown bats (Myotis luafugus (Le Conte, 1831); ~7 g) and silver-haired bats (Lasionycteris noctivagans (Le Conte, 1831); ~13 g), as the latter two species roost in tree crevices or cavities that are more thermally buffered than the foliage roosts of hoary bats. We measured core body temperature ([T.sub.b]; passive integrated transponder tags), evaporative water loss, and resting metabolic rate (flow-through respirometry) while exposing individuals to a stepped profile of increasing air temperature ([T.sub.a]) from ~30 [degrees]C in ~2 [degrees]C increments. Experiments were terminated when individuals became hyperthermic ([T.sub.b] [approximately equal to] 42.5 [degrees]C), with maximum [T.sub.a] ([T.sub.a,max]) ranging from 42.0 to 49.7 [degrees]C. As predicted, hoary bats had the highest heat tolerance and evaporative cooling capacity, reaching [T.sub.a,max] ~2.4 and 1.2 [degrees]C higher than little brown and silver-haired bats, respectively. Our results are consistent with the hypothesis that heat tolerance of bats is correlated with roost microclimates, although interspecific variation in body mass and phylogeny may confound these conclusions. Key words: heat tolerance, evaporative cooling capacity, hyperthermia, roost temperature, Myotis luafugus, little brown bat, Lasionycteris noctivagans, silver-haired bat, Lasiurus cinereus, hoary bat, Yinpterochiroptera. Nous avons vérifié l'hypothèse voulant que les variations interspécifiques de la tolérance à la chaleur et de la capacité de refroidissement par évaporation chez les chiroptères soient corrélées aux microclimats des gîtes diurnes, en utilisant trois chauves-souris de la famille des vespertilionidés présentes en sympatrie en été en Saskatchewan (Canada). Nous avions prédit que la tolérance à la chaleur des chauves-souris cendrées (Lasiurus cinereus (Palisot de Beauvois, 1796); ~22 g) serait plus grande que celles des vespertilions bruns (Myotis lucifugus (Le Conte, 1831); ~7 g) et des chauves-souris argentées (Lasionycteris noctivagans (Le Conte, 1831); ~13 g), puisque les gîtes diurnes de ces deux dernières espèces sont des fentes ou cavités dans les arbres caractérisées par des températures moins variables que les gîtes dans le feuillage des chauves-souris cendrées. Nous avons mesuré la température corporelle centrale ([T.sub.b]; radioétiquettes passives intégrées), la perte d'eau par évaporation et le métabolisme au repos (respirométrie dynamique), alors que les spécimens étaient exposés à des températures de l'air ([T.sub.a]) commençant à ~30 [degrees]C et augmentant par incréments de ~2 [degrees]C. Les manipulations cessaient que les spécimens devenaient hyperthermiques ([T.sub.b] [approximately equal to] 42,5 [degrees]C), les Ta maximums ([T.sub.a,max]) allant de 42,0 à 49,7 [degrees]C. Comme prévu, les chauves-souris cendrées présentent la plus forte tolérance à la chaleur et la plus grande capacité de refroidissement par évaporation, atteignant des [T.sub.a,max] de ~2,4 et 1,2 [degrees]C supérieures à celles des vespertilions bruns et des chauves-souris argentées, respectivement. Nos résultats concordent avec l'hypothèse selon laquelle la tolérance à la chaleur des chauves-souris est corrélée aux microclimats des gîtes, bien que des variations interspécifiques de la masse corporelle et la phylogénie puissent nécessiter de nuancer ces conclusions. [Traduit par la Rédaction] Mots-clés : tolerance a la chaleur, capacite de refroidissement par evaporation, hyperthermie, temperature du gite, Myotis lucifugus, vespertilion brun, Lasionycteris noctivagans, chauve-souris argentee, Lasiurus cinereus, chauve-souris cendree, yinpterochiropteres., Introduction Free-ranging endotherms frequently encounter environmental temperatures above their normothermic body temperature ([T.sub.b]), for example, while foraging in sunlit microsites or occupying hot roosts during the day (e.g., Henshaw and [...]

Researchers in the Global South (GS, developing countries) make valuable contributions to the field of comparative physiology, but face economic and scientific disparities and several unique challenges compared with colleagues in the Global North (developed countries). This Perspective highlights some of the challenges, knowledge gaps and disparities in opportunity faced by GS researchers, especially those at early-career stages. We propose collaborative solutions to help address these issues, and advocate for promoting investment and cultural and societal change for a more inclusive research community. Additionally, we highlight the role of GS researchers in contributing expert knowledge on local biodiversity and the environment; this knowledge can help to shape the future of comparative physiology, allowing us to achieve a better understanding of the evolution of physiological mechanisms and to develop innovative solutions to environmental and biomedical challenges. With this Perspective, we hope to highlight the need to foster a more diverse, equitable and inclusive research landscape in comparative physiology; one that empowers GS scientists to address the global challenges associated with biodiversity loss, climate change and environmental pollution., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)