Capturing ongoing diversification: a complete phylogeny of an avian radiation using dense sampling of tips

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The Neotropical region includes Central and South America and the Caribbean and contains the highest diversity of birds of any region on the planet. Roughly one in three birds in the Neotropics is from a group called the suboscine passerines. The suboscines are diverse in form and function and are an important component of the bird life in habitats ranging from tropical rainforests to alpine grasslands and rocky coastlines. The origins of this diversity – the tempo and mode of species formation – have been studied through prior NSF-funded work. However, this work did not contain sufficient sampling to capture the most recent and ongoing speciation events. These recent speciation events are the most critical for evolutionary research because they tell us about where and why new species are forming currently. High-resolution sampling also provides the information necessary to identify new species and revise species classification. In this project, the investigators are completely sampling suboscine diversity, obtaining new vouchered samples and adding genomic data from 1,548 missing populations in order to resolve the species limits in the group and provide a comprehensive framework for research on diversification. This work integrates a concerted program for recruiting and retaining underrepresented students in biodiversity science in three underserved geographic areas: Appalachian Tennessee, Louisiana, and majority Hispanic communities in west Texas. It involves a new program on avian diversity at the K–12 level, development of a dedicated module on biodiversity genetics for undergraduate Genetics students, and support for graduate and post-graduate researchers to conduct research. The unifying principle of this project is that a completely sampled phylogeny of all suboscine evolutionary units is needed to provide the foundation for systematic revision as well as improved capacity for research on speciation and evolution in the group. The researchers are leveraging the well-sampled suboscine passerine radiation (1,323 currently recognized species, plus 1,875 subspecies) to complete two primary aims. First, they are using field work, existing genomic resources, and historical DNA approaches to obtain genomic data from all 1,548 unsampled taxa, including all subspecies, in the group and estimate a complete, time-calibrated phylogeny. Second, they are using this phylogeny to conduct a re-assessment and revision of suboscine systematics at the genus, species, and subspecies levels within a hypothesis-testing framework. Because the phylogeny contains information on all lineage divergences in suboscines even those between the youngest taxa, it provides an invaluable resource for researchers interested in detailed diversification dynamics, modes of speciation, avian evolution at a range of timescales, molecular evolution, and species concepts and delimitation. The new specimens, genetic samples, and genomic data being obtained are also invaluable. Together, this work and its results are providing a high-resolution picture of how diversity has evolved in a species-rich tropical group that contributes to one of the major biodiversity hotspots on the planet.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.