New avian papers:
Juliana A. Vianna, FlÃvia A. N. Fernandes, MarÃa JosÃ Frugone, Henrique V. FigueirÃ, Luis R. Pertierra, Daly Noll, Ke Bi, Cynthia Y. Wang-Claypool, Andrew Lowther, Patricia Parker, Celine Le Bohec, Francesco Bonadonna, Barbara Wienecke, Pierre Pistorius, Antje Steinfurth, Christopher P. Burridge, Gisele P. M. Dantas, Elie Poulin, W. Brian Simison, Jim Henderson, Eduardo Eizirik, Mariana F. Nery, and Rauri C. K. Bowie (2020)
Genome-wide analyses reveal drivers of penguin diversification.
Proceedings of the National Academy of Sciences (advance online publication)
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2006659117/-/DCSupplemental
Penguins have long been of interest to scientists and the general public, but their evolutionary history remains unresolved. Using genomes, we investigated the drivers of penguin diversification. We found that crown-group penguins diverged in the early Miocene in Australia/New Zealand and identified Aptenodytes (emperor and king penguins) as the sister group to all other extant penguins. Penguins first occupied temperate environments and then radiated to cold Antarctic waters. The Antarctic Circumpolar Currentâs (ACC) intensification 11.6 Mya promoted penguin diversification and geographic expansion. We detected interspecies introgression among penguins, in some cases following the direction of the ACC, and identified genes acting on thermoregulation, oxygen metabolism, and diving capacity that underwent adaptive evolution as they progressively occupied more challenging thermal niches.
Penguins are the only extant family of flightless diving birds. They currently comprise at least 18 species, distributed from polar to tropical environments in the Southern Hemisphere. The history of their diversification and adaptation to these diverse environments remains controversial. We used 22 new genomes from 18 penguin species to reconstruct the order, timing, and location of their diversification, to track changes in their thermal niches through time, and to test for associated adaptation across the genome. Our results indicate that the penguin crown-group originated during the Miocene in New Zealand and Australia, not in Antarctica as previously thought, and that Aptenodytes is the sister group to all other extant penguin species. We show that lineage diversification in penguins was largely driven by changing climatic conditions and by the opening of the Drake Passage and associated intensification of the Antarctic Circumpolar Current (ACC). Penguin species have introgressed throughout much of their evolutionary history, following the direction of the ACC, which might have promoted dispersal and admixture. Changes in thermal niches were accompanied by adaptations in genes that govern thermoregulation and oxygen metabolism. Estimates of ancestral effective population sizes (Ne) confirm that penguins are sensitive to climate shifts, as represented by three different demographic trajectories in deeper time, the most common (in 11 of 18 penguin species) being an increased Ne between 40 and 70 kya, followed by a precipitous decline during the Last Glacial Maximum. The latter effect is most likely a consequence of the overall decline in marine productivity following the last glaciation.