Modernization, diversification, and domination: Macroevolutionary origins of living bird diversity

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Modern birds comprise over 10,000 living species, occupying a dizzying range of niche space and inhabiting virtually every corner of the modern world. In order to study the origins of this spectacular diversity, as well as the stepwise sequence by which biologically modern birds came to be, insights from the Mesozoic fossil record of feathered dinosaurs are critical, as are early Cenozoic fossils documenting the rise of modern birds. Here, I outline an ambitious research programme composed of distinct, yet broadly overlapping lines of inquiry aimed at illuminating the early evolutionary history of birds. This work will bring us closer than ever before to a more complete understanding of the origins of one of Earth's most dominant living groups of organisms. The proposed programme builds on my high-profile research in multiple areas of avian evolutionary biology and will deliver fundamental insights into some of the most important and longest-standing questions in avian macroevolution. Work will be divided into projects aimed at clarifying How, Where, and When the spectacular diversity of living birds, their specialised features, and their extraordinary phenotypic disparity have arisen. These studies will draw on abundant new three-dimensional data from pivotally important undescribed fossils, cutting edge visualisation techniques, and a wealth of novel phenotypic and genomic data from ongoing international collaborations.i) How: Tracing the origin of the modern avian skull, and sophisticated avian flight. Three dimensionally preserved fossils are extremely rare among the closest relatives of modern birds from the Age of Dinosaurs. Exquisite new fossils from this interval, uniquely, exhibit both three-dimensionally preserved skulls and skeletons. High-resolution CT scanning combined with three-dimensional mathematical analyses will elucidate the origin of the modern avian brain, and cutting-edge range-of-motion analyses will illuminate how the modern avian flight stroke evolved.ii) Where: The origin of modern avian geographic patterns, and the role of historical climate fluctuations in structuring avian distributions. We have previously shown that the geographic distributions of many groups of modern birds have fluctuated dramatically through their evolutionary history, but the causes of these inter-continental range shifts are unclear. By combining the latest palaeoclimate models with cutting-edge 'niche modelling' approaches, we will test-for the first time-the extent to which climatic change over the last 66 million years may have contributed to these patterns and predict future climate-driven geographic changes.iii) When: Refining the timing of the modern avian radiation. By taking a three-pronged approach (developing new divergence time models, generating new sequence data from understudied species, and evaluating new fossil calibrations) we are poised to generate the first comprehensive and accurately time-scaled picture of the modern bird tree of life, a fundamental step toward discerning the patterns and processes that have generated Earth's modern bird biodiversity. This will also shed light on how major events in Earth history, like the mass extinction event that killed the giant dinosaurs, have shaped avian evolution. This interdisciplinary project will have impacts on teaching, museum exhibition, digital collections building, and media, and will involve many early career scientists. New data from this project (e.g. CT scans of key modern birds and new fossils) will provide a digital legacy to be made freely available to all. These data will facilitate myriad future studies on avian evolution, and combined with media exposure accompanying publications, will educate both young and old about evolution and palaeontology. To this end, visual data from this project will be incorporated into an exhibit at the Sedgwick Museum of Earth Sciences, allowing the public to manipulate both digital and physical specimens.