Dynamic rivers have contributed to the rich bird diversity of the Amazon

A photo from a recent scientific expedition to the Amazon by the study’s lead author, Lukas Musher. 1 credit

One of the most controversial questions in evolutionary biology is: how did the Amazon become so species-rich? A new study focused on birds examines how the movements of rivers in the Amazon have contributed to the exceptional biological diversity of this region. The research team, led by the American Museum of Natural History, found that small river systems change over time, spurring the evolution of new species. The findings also reveal previously unknown bird species in the Amazon that are only found in small areas alongside these dynamic river systems, putting them at high risk of imminent extinction. The study is detailed today in the journal Scientists progress.

The lowland rainforests of the Amazon basin are home to more diversity than any other terrestrial ecosystem on the planet. It is also a globally significant biome containing about 18% of all trees on Earth and carrying more fresh water than the seven largest river basins combined. Researchers have long wondered and passionately debated how the Amazon’s rich biodiversity arose and accumulated.

“Early evolutionary biologists like Alfred Russel Wallace noticed that many species of primates and birds differ on opposite sides of the Amazon, and ornithologists now know that the rivers are associated – in one way or another. from another – the origin of many avian species,” said the study’s lead author, Lukas Musher, a postdoctoral researcher at Drexel University’s Academy of Natural Sciences and recent holder of a a doctorate in comparative biology. graduated from the Richard Gilder Graduate School of the American Museum of Natural History. “Furthermore, accumulating geological evidence has suggested that these rivers are highly dynamic, moving through the South American landscape over relatively short periods of time, on the order of thousands or tens of thousands of years. “

To study how the movement of rivers through the landscape influenced the accumulation of bird species in the Amazon, researchers sequenced the genomes of six species of Amazonian birds.

“Even though birds can fly, our study confirmed that current rivers through the southern Amazon rainforest, even relatively small ones, are very effective at isolating populations of these six species, leading to divergence genomics and ultimately speciation,” said the study’s lead author. Joel Cracraft, Lamont Curator and Curator in charge of the Museum’s Department of Ornithology.

However, because these rivers move across the landscape on different time scales, their movements can have varying consequences for bird species: when river rearrangements occur rapidly, bird populations on either side can merge before to have had the time to differentiate themselves; when river changes occur slowly, species have more time to move away from each other; and when rivers change at intermediate rates, bird populations diverge, then join and coexist as a river moves.

Scientists have also identified distinct populations of birds that should be described as separate species, but have been considered a single species until now.

“Although we know that Amazonian biodiversity is unmatched by any other terrestrial ecosystem, we have demonstrated that its species richness can be grossly underestimated, even in well-studied groups such as birds,” Musher said. “Our results support those of other studies that have reported small-scale patterns of diversity in the southern Amazon basin – a region threatened by rapid and continued deforestation – but this diversity is generally not recognized. Many distinct populations are relatively young and endemic to a small region of the Amazon, which means that many of the birds in the Amazon may be in imminent danger of extinction.

There may be more bird species in the tropics than we know

More information:

Lukas J. Musher, rearrangements of the river network promote speciation in birds of the Amazon lowlands, Scientists progress (2022). DOI: 10.1126/sciadv.abn1099. www.science.org/doi/10.1126/sciadv.abn1099

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American Museum of Natural History

Dynamic Rivers Have Contributed to Amazon’s Rich Bird Diversity (2022, April 8)
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