Researchers took ancient DNA from Caribbean parrots, compared it to contemporary bird genetics, and discovered that two species that were thought to be island-specific have a wider range. This evidence highlights the vast parrot endangerment and demonstrates how human contact through thousands of years, including trading and relocation, has obscured knowledge of their native habitats and historical distributions.
According to a recent study in PNAS, ancient DNA from Caribbean parrots has been successfully extracted by scientists. The team discovered that two species that were earlier thought to be native to particular islands were once more widespread and diversified by comparing this DNA with sequences from present birds and by looking at fossils and archaeological samples.
The findings contribute to the understanding of how parrots, with 28% of all species being classified Endangered, quickly become the most endangered group of birds in the world. This is especially true with island-dwelling parrots.
When Christopher Columbus made his first trip to the Caribbean in 1492, he observed that flocks of parrots were so numerous that they “obscured the sun.” Large particolored macaws to smaller parrots, more than half of the Caribbean’s parrot species are no longer alive.
The lack of information on the past distributions of the remaining parrot species hinders biologists’ efforts to conserve them. They have a tangled history with humans, which is mostly to blame.
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According to lead author Jessica Oswald, a senior biologist with the U.S. Fish and Wildlife Service Forensics Lab, “people have always been obsessed with parrots.” “For thousands of years, indigenous peoples have transported parrots between islands and across continents. The practise was later carried on by European colonists, and it is still being used today.
It is challenging to understand how parrots came to be where they are today because of centuries of interchange and trade. It’s unknown if native parrots originated on the islands they live on or were similarly moved there, but half of the 24 parrot species that today occupy the Caribbean were introduced from other regions.
Parrots are occasionally found in ancient sites because to their popularity among people. Their bones have been found in trash heaps known as middens, together with shells, fish bones, and other leftover food scraps.
The authors pieced together the long history of parrots in the genus Amazona, focusing on two species — the Cuban (A. leucocephala) and Hispaniolan (A. ventralis) parrots — for which they could obtain ancient DNA samples. Credit: Kristen Grace
According to senior author Michelle LeFebvre, curator of South Florida Archaeology and Ethnography at the Florida Museum of Natural History, “there are records of parrots being kept in homes, where they were valued for their feathers and, in some cases, possibly as a source of food.”
Comparative to other tropical areas, the Caribbean has a very strong fossil record for parrots. However, entire specimens are rarely discovered. Most frequently, their bones are shattered or solitary, making it difficult to identify the species to which they belong.
Co-author David Steadman was excited to see if they could extract any leftover genetic material stored in bone tissue because DNA can provide clear answers where physical comparisons fall short. Oswald had just finished a proof of concept in which she successfully sequenced the first DNA from an extinct Caribbean bird that had been kept in a blue hole for 2,500 years. Oswald worked as a graduate student and postdoctoral associate at the Florida Museum. She later found that an extinct flightless bird from the Caribbean was most closely connected to comparable extinct, ground-dwelling species from Africa and New Zealand using the same techniques.
By concentrating on two species, the Cuban (A. leucocephala) and Hispaniolan (A. ventralis) parrots, for which they could get ancient DNA samples, the authors put together the lengthy history of parrots in the genus Amazona.
With isolated populations in Cuba, the Bahamas, and a few islands in Turks and Caicos, Cuban parrots are currently the more common of the two. They are among the few native parrots in the area that are not in immediate risk of going extinct.
The Hispaniolan parrot has had a more difficult time adjusting to changes caused by humans. It is completely endemic to its namesake island and is protected by the International Union for Conservation of Nature’s Red List as being vulnerable to extinction.
Therefore, it was determined that the majority of the fragmentary fossils discovered outside of Hispaniola and Puerto Rico belonged to the more prevalent Cuban parrots. However, the DNA results revealed a different story. The fact that Hispaniolan parrot fossils were discovered in the Bahamian paleontological sites suggests that this species once ranged through the Bahamas before humans arrived on the islands.
Similar findings show that Cuban parrots formerly lived on the largest island in Turks and Caicos, but they are no longer there.
The discovery of what might be referred to as dark extinctions is one of the study’s most remarkable findings, according to LeFebvre. “We’re discovering diversity that, until we looked more closely at museum specimens, we didn’t even know existed.”
It was also determined that bones from archaeological sites in the Turks and Caicos and from Montserrat, a remote island in the Lesser Antilles, came from Hispaniolan parrots. Since the species is no longer present on the islands, these were probably brought there by humans.
According to Oswald, the first step in preserving what’s left of a species’ diversity is understanding the locations where it historically flourished, both naturally by itself and artificially with human assistance.
We need to rethink what we regard as natural, she continued. Since humans have been modifying the natural world for thousands of years, it is possible that certain species that we believe to be indigenous to a particular region have recently had their ranges reduced by humans. To fully comprehend the long-term impact of humans on variety change, palaeontologists, archaeologists, evolutionary biologists, and museum scientists must collaborate.
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