Dynamic rivers contributed to Amazon's rich bird diversity
Genome-based study also finds new bird species at high risk of imminent extinction

Date:
April 8, 2022
Source:
American Museum of Natural History
Summary:
One of the most contentious questions in evolutionary biology is,
how did the Amazon become so rich in species? A new study focused
on birds examines how the movements of rivers in the Amazon have
contributed to that area's exceptional biological diversity. The
researchers found that as small river systems change over time,
they spur the evolution of new species. The findings also reveal
previously unknown bird species in the Amazon that are only found
in small areas next to these dynamic river systems, putting them
at high risk.



FULL STORY ==========================================================================
One of the most contentious questions in evolutionary biology is, how
did the Amazon become so rich in species? A new study focused on birds
examines how the movements of rivers in the Amazon have contributed to
that area's exceptional biological diversity. The research team, led by
the American Museum of Natural History, found that as small river systems change over time, they spur the evolution of new species. The findings
also reveal previously unknown bird species in the Amazon that are only
found in small areas next to these dynamic river systems, putting them
at high risk of imminent extinction. The study is detailed today in the
journal Science Advances.


==========================================================================
The lowland rainforests of the Amazon River basin harbor more diversity
than any other terrestrial ecosystem on the planet. It is also a
globally important biome containing about 18 percent of all trees on
Earth and carrying more fresh water than the next seven largest river
basins combined. Researchers have long wondered and hotly debate 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 across opposite riverbanks in
the Amazon, and ornithologists now know that rivers are associated --
in one way or another -- with the origin of many avian species," said
the study's lead author Lukas Musher, a postdoctoral researcher at the
Academy of Natural Sciences of Drexel University and a recent comparative biology Ph.D. graduate of the American Museum of Natural History's Richard Gilder Graduate School. "Moreover, accumulating geological evidence has suggested that these rivers are highly dynamic, moving around the South American landscape over relatively short time periods, on the order
of thousands or tens of thousands of years." To investigate how the
movement of rivers across the landscape has influenced the accumulation
of bird species in the Amazon, the researchers sequenced the genomes of
six species of Amazonian birds.

"Even though birds can fly, our study confirmed that current rivers
across the Southern Amazon rainforest, even relatively small ones,
are highly effective at isolating populations of these six species,
which leads to genomic divergence and ultimately speciation," said the
study's senior author Joel Cracraft, Lamont Curator and curator-in-charge
in the Museum's Department of Ornithology.

However, because these rivers move around the landscape at different time scales, their movements can have varying outcomes for bird species: when
river rearrangements occur quickly, populations of birds on each side
can merge before they've had time to differentiate; when river changes
happen slowly, species have a longer time to diverge from one another;
and when rivers change at intermediate rates, bird populations diverge
and then join back together and co-occur when a river moves.

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

"Though we know Amazonian biodiversity is unmatched by any other
terrestrial ecosystem, we demonstrated that its species richness may
be greatly underestimated even in well-studied groups such as birds,"
Musher said. "Our results corroborate those of other studies that have
reported fine-scale patterns of diversity across the southern Amazon basin
-- a region threatened by rapid and ongoing deforestation -- yet this
diversity is generally unrecognized. Many of the distinct populations
are relatively young and endemic to a small Amazonian region, meaning
that a large portion of the Amazon's birds may be threatened with loss
to imminent extinction." Other authors on this study include Melina
Giakoumis, City College of New York; James Albert, University of Louisiana
at Lafayette; Glaucia Del-Rio, Marco Rego and Robb T. Brumfield, Louisiana State University; Camila C. Ribas, Instituto Nacional de Pesquisas da Amazo^nia; Alexandre Aleixo, University of Helsinki, Museu Paraense
Emi'lio Goeldi, and Instituto Tecnolo'gico Vale, Bele'm, Brazil; and
Gregory Thom and Brian Smith, American Museum of Natural History.

This work was funded in part by the American Museum of Natural History's Richard Gilder Graduate Research Fellowship, The Linda Gormezano Memorial
Fund research grant, the Society for Systematic Biologists graduate
student research grant, and NSF/NASA Dimensions US-Biota-Sa?o Paulo
grant # 1241066.


========================================================================== Story Source: Materials provided by
American_Museum_of_Natural_History. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Lukas J. Musher, Melina Giakoumis, James Albert, Glaucia Del-Rio,
Marco
Rego, Gregory Thom, Alexandre Aleixo, Camila C. Ribas,
Robb T. Brumfield, Brian Tilston Smith, Joel Cracraft. River
network rearrangements promote speciation in lowland Amazonian
birds. Science Advances, 2022; 8 (14) DOI: 10.1126/sciadv.abn1099 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220408142957.htm

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