Sedimentary Metagenomics Reveal Avian Community Transitions From the Last Glacial Maximum to the Holocene.

The transition from the Last Glacial to the Holocene was marked by significant warming. This forced a compositional turnover of terrestrial plant and mammal communities discovered by diverse palaeoecological techniques. In this study, we analysed ancient environmental DNA with shotgun metagenomics from eight lake sediment cores, collected in northern Eurasia and Alaska, to elucidate the relationship of past bird communities and vegetation structure across the last 21,000 years. We leveraged all DNA reads assigned to the class 'Aves' to characterise the compositional changes of the bird community. The dominance of chicken birds (Galliformes, mainly ptarmigans) during the Last Glacial Maximum turned into a higher taxonomic bird diversity with increased numbers of songbird, raptor and waterfowl abundances and genera. This went along with the late glacial loss of the steppe-tundra and the increase of shrub and tree cover. Compared to the northern boreal areas, vegetation and bird communities were more stable in the northern tundra sites, where open landscapes prevailed throughout. Metagenomics significantly contribute to the reconstruction of past avian community changes and thus have high potential to support the predictions of distribution changes in the course of future ecosystem change.