Ancient DNA reveals new insights into the history and diversity of Caribbean parrots

In a recent study published in PNAS, researchers have achieved a remarkable feat: extracting ancient DNA from Caribbean parrots. This genetic material was compared with the DNA of modern birds, shedding light on the history of these colorful creatures. The study revealed that two parrot species believed to be unique to specific islands were once more widespread and diverse.

These findings offer insights into why parrots, especially those on islands, have become the world’s most endangered group of birds, with 28% of all species facing threats to their survival. The contrast is striking when we consider Christopher Columbus’ accounts during his first voyage to the Caribbean in 1492 when he observed parrot flocks so numerous that they darkened the sky. Today, over half of the Caribbean’s parrot species have vanished, from majestic macaws to tiny parrotlets.

Conservationists striving to protect the remaining parrot species face a daunting challenge due to the complexity of these birds’ interactions with humans throughout history. “People have always been captivated by parrots,” noted lead author Jessica Oswald, a senior biologist with the U.S. Fish and Wildlife Service Forensics Lab. Indigenous peoples and European colonists alike transported parrots across continents and between islands, and this practice continues today.

Centuries of trade and exchange make it difficult to trace the origins of parrot populations. For instance, half of the 24 parrot species currently found in the Caribbean were introduced from elsewhere, making it uncertain whether native parrots evolved on the islands or were brought there.

Fortunately, parrots have left traces of their existence in archaeological sites. Their bones, discovered alongside remnants of past meals in refuse piles known as middens, offer valuable insights into their history. “Parrots were often kept in homes for their feathers and, sometimes, as a potential source of food,” explained senior author Michelle LeFebvre, curator of South Florida archaeology and ethnography at the Florida Museum of Natural History.

Additionally, the Caribbean boasts a relatively rich fossil record for parrots compared to other tropical regions, though the specimens are often fragmented. Enter DNA analysis, which can provide definitive answers where physical comparisons fall short. Co-author David Steadman was eager to explore if any genetic material could be extracted from parrot bone tissue.

Oswald, who previously sequenced DNA from an extinct Caribbean bird preserved in a blue hole for 2,500 years, applied the same methods to reveal that an extinct flightless Caribbean bird was closely related to extinct ground-dwelling birds from Africa and New Zealand.

The study focused on the genus Amazona, particularly two species: the Cuban (A. leucocephala) and Hispaniolan (A. ventralis) parrots, from which they obtained ancient DNA samples.

Of the two, Cuban parrots currently have a more extensive range, with isolated populations in Cuba and some Bahamian islands. They are among the few native parrots in the region not on the brink of extinction.

On the other hand, the Hispaniolan parrot has struggled to adapt to human-induced changes. It is listed as vulnerable to extinction and is found only on its namesake island.

Interestingly, the DNA results challenged previous assumptions. Fossils from Bahamian sites were, in fact, from Hispaniolan parrots, suggesting that this species once inhabited the Bahamas before human arrival. Similarly, Cuban parrots were formerly present on the largest island in the Turks and Caicos but are now absent.

This study has unveiled what can be called “dark extinctions,” revealing lost diversity that wasn’t known until researchers closely examined museum specimens.

Bones from archaeological sites in the Turks and Caicos and Montserrat were also identified as belonging to Hispaniolan parrots, likely transported by humans, as the species is no longer found on those islands.

Jessica Oswald emphasized the importance of understanding where these species once thrived, whether naturally or with human intervention, as the first step toward conserving their remaining diversity. The study underscores the profound impact humans have had on the natural world over millennia, highlighting the need for interdisciplinary collaboration among paleontologists, archaeologists, evolutionary biologists, and museum scientists to unravel the long-term consequences of human influence on biodiversity.

Co-authors on the study include Brian Smith of the American Museum of Natural History, Julie Allen of Virginia Tech, and Robert Guralnick of the Florida Museum of Natural History.

Source: Florida Museum of Natural History

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