Brain surface morphology and ecological and macroevolutionary inferences of avian New World suboscines (Aves, Passeriformes, Tyrannides)

Abstract

The New World suboscines (Passeriformes and Tyrannides) are one of the biggestendemic vertebrate radiations in South America, including the families Furnariidaeand Tyrannidae. Avian brain morphology is a reliable proxy to study their evolution.The aim of this work is to elucidate whether the brains of these families reflectthe ecological differences (e.g., feeding behavior) and to clarify macroevolutionaryaspects of their neuroanatomy. Our hypotheses are as follows: Brain size is similarbetween both families and with other Passeriformes; brain morphology in Tyrannidesis the result of the pressure of ecological factors; and brain disparity is low sincethey share ecological traits. Skulls of Furnariidae and Tyrannidae were micro-computedtomography–scanned, and three-dimensional models of the endocast were generated.Regression analyses were performed between brain volume and body mass. Linear andsurface measurements were used to build phylomorphospaces and to calculate theamount of phylogenetic signal. Tyrannidae showed a larger brain disparity than Furnariidae,although it is not shaped by phylogeny in the Tyrannides. Furnariidae presentenlarged Wulsts (eminentiae sagittales) but smaller optic lobes, while in Tyrannidae, itis the opposite. This could indicate that in Tyrannides there is a trade-off between thesize of these two visual-related brain structures.