16. Kontopoulos, D.-G.^✉, Levesque, D.L., and Hiller, M.^✉ (2025). Numerous independent gains of daily torpor and hibernation across endotherms, linked with adaptation to diverse environments. Functional Ecology.

Abstract:

1. Many endotherms from diverse taxonomic groups can respond to environmental changes through torpor, that is, by greatly reducing their energy expenditure for up to 24 hours (daily torpor) or longer (hibernation). We currently have a poor understanding of how torpor evolved across endotherms and its associations with physiological traits and ecological factors.
2. To fill this gap, we thoroughly examine the evolutionary patterns of torpor and its links with 21 key physiological and ecological variables across 1338 extant endotherms.
3. We find that daily torpor and hibernation are parts of an evolutionary torpor continuum, and that there are several, albeit weak, associations between torpor and species' physiological or environmental characteristics. Furthermore, we show that early endotherm ancestors likely did not hibernate and that this trait evolved multiple times in independent lineages.
4. Overall, our results suggest that the remarkable variation in torpor patterns across extant endotherms cannot solely be attributed to environmental niches, but partly arises from independent gains of daily torpor and hibernation in various clades.

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