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 extinction.
The lowland rainforests of the Amazon River basin harbor(藏匿) more diversity than any other ecosystem on the planet. It is also a globally important biome(生物群落)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 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 across opposite riverbanks in the Amazon,” said the study’s lead author Lukas Musher.“ 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(基因组)of six species of Amazonian birds.
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 combine before they’ve had time to differ; when river changes happen slowly, species have a longer time to diverge from one another.
【小题1】What does the underlined word “spur” in Paragraph 1 mean?| A．Stimulate. | B．Renew. | C．Pursue. | D．Interrupt. |
| A．What the Amazon’s biodiversity indicates. |
| B．How Amazon bird species are at risk of distinction. |
| C．Whether the Amazon has the richest biodiversity. |
| D．How the Amazon’s biodiversity was formed. |
| A．There are six species of American birds. |
| B．River movement may lead to the Amazon’s biodiversity. |
| C．Most species differ across opposite Amazon riverbanks. |
| D．Rivers move very slowly in South America. |
| A．The location of river movement. | B．The populations of birds. |
| C．The speed of river movement. | D．The amount of the genomes. |
