Comparative genomics indicate multiple genetic routes to the evolution of torpor in placental mammals

Torpor is a key survival strategy that many avian and mammalian lineages evolved in response to challenging environmental conditions. Whether the independent evolution of torpor in different lineages involved changes in the same genes remains poorly understood. Here, we performed comparative screens across 190 placental mammal genomes to comprehensively examine associations between loss, positive selection and evolutionary rate shifts in individual protein-coding genes and evolutionary shifts in torpor use. We find that gene-torpor associations are highly clade-specific, with no gene being able to explain the majority of torpor shifts across the phylogeny of placental mammals. Instead, a relatively higher but limited extent of evolutionary convergence can be detected at the pathway level. Our results suggest that torpor emerged through several genetic routes in placental mammals, which likely explains the vast diversity of torpor use patterns that can be observed among torpor-capable species today.