Serendipitous timing of a developmental shift stimulated the greatest bird radiation

Speaker: Prof. Daniel Field (University of Cambridge)
Series: Department of Earth Sciences Seminars (downtown)

Neoaves, one of the three deepest crown bird subclades, comprises over 95% of living bird diversity. Unlike Palaeognathae and Galloanserae (the other two extant avian subclades), Neoaves is thought to have undergone an early burst of diversification attributed to rapid ecological niche-filling in the aftermath of the Cretaceous–Palaeogene (K–Pg)mass extinction. However, factors underpinning the differential post-K–Pg niche-filling potential of Neoaves relative to Palaeognathae and Galloanserae, including the possibility of intrinsic biological differences conferring enhanced neoavian evolvability in the early Cenozoic Era, remain largely unexamined. This talk will explore the influence of circum-K–Pg evolutionary shifts in developmental mode on the neoavian radiation, focusing on the selective drivers influencing keyparameters related to the avian altricial–precocial spectrum. Results illustrate that the origin of parental feeding along the neoavian stem lineage was a prerequisite for the evolution of high nest attendance strategies, enabling both transitions to novel foraging modes as well as increases in the flexibility and duration of developmental trajectories. These, in turn, facilitated the early-Cenozoic emergence of derived skeletal morphologies, proportions, and associated ecological disparity within Neoaves. The scenario that emerges is one of a ‘macroevolutionary cascade’, in which sequential transitions to more altricial developmental strategies unique to Neoaves collectively represent a key innovation facilitating the clade’s rapid early-Cenozoic niche colonisation and explosive diversification, revealing the interplay between the advent of avian developmental mode disparity and ecological expansion in the wake of the K–Pg extinction.