Niche expansion and adaptive divergence in the global radiation of crows and ravens

The processes that allow some lineages to diversify rapidly at a global scale remain poorly understood. Although earlier studies emphasized the importance of dispersal, global expansions expose populations to novel environments and may also require adaptation and diversification across new niches. In this study, we investigated the contributions of these processes to the global radiation of crows and ravens (genus Corvus). Combining a new phylogeny with comprehensive phenotypic and climatic data, we show that Corvus experienced a massive expansion of the climatic niche that was coupled with a substantial increase in the rates of species and phenotypic diversification. The initiation of these processes coincided with the evolution of traits that promoted dispersal and niche expansion. Our findings suggest that rapid global radiations may be better understood as processes in which high dispersal abilities synergise with traits that, like cognition, facilitate persistence in new environments.This research was funded by NSF award number DEB 1841470 to CB. JGP was additionally supported by a Juan de la Cierva fellowship (ref FJCI‐2014‐20380) from the Ministry of Science of the Spanish government, by two Synthesis grants from the European Union (refs FR-TAF-7024 and GB-TAF-6677) and by a research fellowship from the Field Museum of Natural History. DS was supported by MICINN (CGL2017-90033-P and PID2020-119514GB-I00) and FS by funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 838998