Environmental variation and the evolution of large brains in birds

• Published in: Nature communications Vol. 7; no. 1; pp. 13971 - 8
• Main Authors: Sayol, Ferran, Maspons, Joan, Lapiedra, Oriol, Iwaniuk, Andrew N., Székely, Tamás, Sol, Daniel
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 22.12.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 631/158/2039; 631/158/851; 631/158/856; 631/181/757; Animal cognition; Animal Migration; Animals; Behavior, Animal; Biological Evolution; Bird migration; Birds; Birds - anatomy & histology; Birds - classification; Birds - physiology; Body Size; Brain; Brain - anatomy & histology; Brain - physiology; Cognition; Ecosystem; Environment; Evolution & development; Humanities and Social Sciences; Hypotheses; Models, Biological; multidisciplinary; Neurosciences; Organ Size; Phylogenetics; Phylogeny; Principal Component Analysis; Productivity; Remote sensing; Science; Science (multidisciplinary); Selection, Genetic; Species Specificity; Spain
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13971

Environmental variability has long been postulated as a major selective force in the evolution of large brains. However, assembling evidence for this hypothesis has proved difficult. Here, by combining brain size information for over 1,200 bird species with remote-sensing analyses to estimate temporal variation in ecosystem productivity, we show that larger brains (relative to body size) are more likely to occur in species exposed to larger environmental variation throughout their geographic range. Our reconstructions of evolutionary trajectories are consistent with the hypothesis that larger brains (relative to body size) evolved when the species invaded more seasonal regions. However, the alternative—that the species already possessed larger brains when they invaded more seasonal regions—cannot be completely ruled out. Regardless of the exact mechanism, our findings provide strong empirical support for the association between large brains and environmental variability. Environmental variation has been hypothesized to favour the evolution of large brains capable of adjusting behaviour to changing circumstances. Here, Sayol et al . find that across more than 1200 bird species, species with relatively large brains are indeed associated with more variable habitats.