Oldřich Tomášek, Lukáš Bobek, Tereza Kauzálová, Ondřej Kauzál, Marie Adámková, Kryštof Horák, Kampath A. Kumar, Judith Pouadjeu Manialeu, Pavel Munclinger, Eric Djomo Nana

Macrophysiological research is vital to our understanding of mechanisms underpinning global life history variation and adaptation under diverse environments. Birds represent an important model taxon in this regard, yet our knowledge is limited to only a few physiological traits, mostly studied in temperate and Neotropical species. Here, we examined latitudinal and elevational variation in an emerging biomarker of physiological pace of life, blood glucose concentration, collected from 61 European temperate and 99 Afrotropical passerine species. Our data suggest that the slow physiological pace-of-life syndrome, indicated by lower baseline glucose level and stronger stress response, evolves convergently in lowland tropical birds across continents and is shaped by their low fecundity. In contrast, elevational variation in blood glucose levels implied a unique montane pace-of-life syndrome combining slow-paced life histories with fast-paced physiology. The observed patterns suggest an unequal importance of life history in shaping physiological adaptations associated with latitude and elevation.