Tempo and Pattern of Avian Brain Size Evolution

BALANOFF, AMY M.; BHULLAR, BHART-ANJAN S.; BURLEIGH, J. GORDON; CORFIELD, JEREMY R.; EARLY, CATHERINE M.; SMITH, N. ADAM; GOLD, MARIA EUGENIA LEONE; BOURDON, ESTELLE; LEFEBVRE, LOUIS; CLARKE, JULIA A.; MORHARDT, ASHLEY; DEGRANGE, FEDERICO J.; ROTHMAN, RYAN S.; FIELD, DANIEL J.; TORRES, CHRISTOPHER R.; KIMBALL, REBECCA T.; WATANABE, AKINOBU; MARUGÁN-LOBÓN, JESÚS; ZANNO, LINDSAY E.; NORELL, MARK A.; SCOFIELD, R. PAUL; VAN TUINEN, MARCEL; WITMER, LAWRENCE M.; JARVIS, ERICH D.; KSEPKA, DANIEL T.; BEVER, GABRIEL S.; BRAUN, EDWARD L.; COLBERT, MATTHEW W.; DE PIETRI, VANESA L.; GIGNAC, PAUL M.; KAWABE, SOICHIRO; MONGLE, CARRIE S.; RIDGELY, RYAN C.; TAMBUSSI, CLAUDIA P.; WALSH, STIG A.; WRIGHT, ALEXANDRA K.; SMAERS, JEROEN B.

CURRENT BIOLOGY

CELL PRESS

Año: 2020 vol. 30 p. 1 - 11

0960-9822

Relative brain sizes in birds can rival those of primates, but large-scale patterns and drivers of avianbrain evolution remain elusive. Here, we explore the evolution of the fundamental brain-body scaling relationship across the origin and evolution of birds. Using a comprehensive dataset sampling> 2,000 modern birds, fossil birds, and theropod dinosaurs, we infer patterns of brain-body co-variation in deep time. Our study confirms that no significant increase in relative brain size accompanied the trend towardminiaturization or evolution of flight during the theropod-bird transition. Critically, however, theropodsand basal birds show weaker integration between brain size and body size, allowing for rapid changes in the brain-body relationship that set the stage for dramatic shifts in early crown birds. We inferthat major shifts occurred rapidly in the aftermath of the Cretaceous-Paleogene mass extinction withinNeoaves, in which multiple clades achieved higher relative brain sizes because of a reduction in bodysize. Parrots and corvids achieved the largest brains observed in birds via markedly different patterns. Parrots primarily reduced their body size, whereas corvids increased body and brain size simultaneously(with rates of brain size evolution outpacing rates of body size evolution). Collectively, these patternssuggest that an early adaptive radiation in brain size laid the foundation for subsequent selection andstabilization.