Latest news with #Dipsosaurus
Yahoo
23-03-2025
- Science
- Yahoo
Iguanas floated 5,000 miles from North America to Fiji on vegetation rafts, new study finds
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. Around 34 million years ago, the ancestors of modern iguanas likely embarked on what may be the longest overwater journey undertaken by a nonhuman, land-dwelling vertebrate species. Starting off the epic trek from the western coast of North America, these iguanas traveled nearly 5,000 miles (8,000 kilometers) — one-fifth of the Earth's circumference — across the Pacific Ocean, eventually arriving in Fiji, according to a new study. Using genetic evidence, researchers propose that these iguanas made the extraordinary voyage by rafting on floating vegetation, possibly composed of uprooted trees or plants. For decades, scientists have debated how Fiji's iguanas arrived. Previous theories suggested that an extinct species of iguana rafted from the Americas without a clear timeline, while others proposed that the lizards migrated overland from Asia or Australia, said lead study author Dr. Simon Scarpetta, an assistant professor at the University of San Francisco. Scarpetta conducted this research during his National Science Foundation postdoctoral fellowship at the University of California, Berkeley, and in his current role. The findings, published Monday in the journal Proceedings of the National Academy of Sciences, help clarify the long-standing mystery of how these reptiles reached such remote islands. Scarpetta and his team aimed to test both the overwater rafting and overland theories, as well as other hypotheses for the biogeographic origin of Fijian iguanas, including dispersal through Antarctica or across the Bering land bridge. Understanding this type of water dispersal could offer new insights into how other species have colonized isolated areas over time, Scarpetta added. Iguanas have already demonstrated an ability to survive long-distance ocean travel, according to an October 1998 study. At least 15 green iguanas appeared on the beaches of Anguilla in the Caribbean in 1995 on rafts of uprooted trees. Researchers determined the lizards likely floated nearly 200 miles (322 kilometers) from Guadeloupe following a hurricane event. Scarpetta noted that this type of overwater rafting is often described as 'sweepstakes' dispersal, a rare event that allows a species to colonize an otherwise unreachable area. Major weather events, such as hurricanes or floods, can dislodge vegetation and carry animals along with it. To determine when iguanas arrived in Fiji, researchers analyzed the genes of 14 living iguana species. The team found that the closest living relative of Fijian iguanas is the Dipsosaurus — a type of desert iguana native to the southwestern United States and northwestern Mexico, according to the new study. Fossil evidence further supports the idea that these iguanas originated in North America, as no fossils of desert iguanas have been found elsewhere in the world, Scarpetta said. The analysis also suggests that the Fijian iguanas diverged from their American ancestors between 34 million and 30 million years ago, settling around the same time as the volcanic formation of the Fijian archipelago, Scarpetta said. This timeline challenges previous theories that iguanas may have made a complex overland journey from South America via Antarctica, which would have happened much later in history, said study coauthor Dr. Jimmy McGuire, a professor of integrative biology at University of California, Berkeley. 'In phylogenetic analyses there is always some degree of uncertainty when trying to predict the timing of divergence events between species,' said Dr. Shane Campbell-Staton, an associate professor of ecology and evolutionary biology at Princeton University, who was not involved in the study. 'In this case, the authors were very thorough in collecting multiple different kinds of genetic data and use(d) multiple different models … to test their hypothesis and find that most of the results are largely in agreement.' While a monthslong voyage across the Pacific may seem impossible, iguanas are surprisingly well-equipped for such extreme travel. 'If you had to pick a vertebrate group that could survive a rafting event across thousands of kilometers of open ocean, iguanas are a great choice,' Scarpetta said. Many iguana species, especially those in desert environments, can endure extreme heat, starvation and dehydration, Scarpetta noted. 'Being ectothermic means that you don't expend many of your food resources or fat reserves maintaining an elevated body temperature,' McGuire said, referring to the metabolic rate of cold-blooded animals. 'Ectotherms can be about 25 times more efficient in this regard than endotherms (warm-blooded animals), so they don't need to eat nearly as much food nor nearly so frequently.' Some estimates suggest that an overwater journey from North America to Fiji could have taken anywhere from four to 12 months. However, newer simulations indicate the trip may have been closer to 2 ½ to four months, Scarpetta said. Despite basic survival challenges, food scarcity likely wouldn't have been a major one. If necessary, the herbivorous reptiles may have been able to feed on their floating vegetation mats, McGuire said. Scientists said they hope that by studying dispersal events, they may be able to predict which species can survive long-distance overwater travel, offering new insights into how animals spread across the globe. 'We now know that overwater dispersal is not only possible, but it has likely played a large role in shaping species diversity on islands around the world,' Campbell-Staton said via email.
Yahoo
17-03-2025
- Science
- Yahoo
After a 5,000-mile float, these iguanas probably set an ocean record
About 34 million years ago, a group of iguanas went on an epic journey. This lofty band of reptiles traveled about 5,000 miles from the western coast of North America all the way to Fiji. Biologists believe that this is the longest known transoceanic dispersal of any land-based vertebrate. The findings are detailed in a study published March 17 in the journal Proceedings of the National Academy of Sciences (PNAS). There are more than 2,100 species in the suborder Iguania. This large group includes other reptiles including chameleons, bearded dragons, and horned lizards. The Western Hemisphere family of lizards are the green ones that most people think of when they picture an iguana. There are 45 different species of Iguanidae in the Caribbean and the tropical, subtropical and desert areas of North, Central, and South America, including the marine iguanas of the Galapágos and the chuckwallas in the American Southwest. However, the four iguana species found on the Pacific islands of Fiji and Tonga are a bit of an outlier. They sit there in the middle of the Pacific Ocean and scientists have long debated how they got there. Overwater dispersal–where terrestrial organisms go from one land mass to another via a body of water–is the primary way that newly formed islands are populated with plants, animals, and even humans. This process often leads to the evolution of new species and ecosystems. This study suggests that the original ancestors of Fiji's iguanas coincided with islands' formation by volcanoes. Scientists estimate their arrival at roughly 34 million years ago based on genetic evidence. Fiji iguanas (Brachylophus) and their closest relatives, the North American desert iguanas (Dipsosaurus) show signs of genetic divergence. Biologists initially proposed that the Fiji iguanas may have descended from an older lineage that was initially more widespread around the Pacific, but has since died out. Another theory was that iguanas traveled from tropical parts of South America and then through Antarctica or even Australia. While there is no genetic or fossil evidence to support these earlier theories, a new genetic analysis does. 'We found that the Fiji iguanas are most closely related to the North American desert iguanas, something that hadn't been figured out before, and that the lineage of Fiji iguanas split from their sister lineage relatively recently, much closer to 30 million years ago, either post-dating or at about the same time that there was volcanic activity that could have produced land,' Simon Scarpetta, a study co-author and University of San Francisco paleontologist and herpetologist, said in a statement. 'That they reached Fiji directly from North America seems crazy,' study co-author and University of California, Berkeley herpetologist Jimmy McGuire said in a statement. 'But alternative models involving colonization from adjacent land areas don't really work for the time frame, since we know that they arrived in Fiji within the last 34 million years or so. This suggests that as soon as land appeared where Fiji now resides, these iguanas may have colonized it. Regardless of the actual timing of dispersal, the event itself was spectacular.' Today's sailors can typically reach Fiji from California in about one month. However, it would take a group of iguanas a bit longer. The reptiles must hop on some flotsam, ride through the doldrums, and across the equator to Fiji and Tonga. Fortunately, iguanas are large and herbivores and can go long periods of time without food and water. Their 'rafts' were also made from uprooted trees that would have provided them with food to eat along the way. 'You could imagine some kind of cyclone knocking over trees where there were a bunch of iguanas and maybe their eggs, and then they caught the ocean currents and rafted over,' Scarpetta said. Based on some fossils found in eastern Asia, biologists believed that some now extinct populations of iguanids lived around the Pacific Rim and island-hopped their way to the middle of the Pacific Ocean. They may have used the Bering Land Bridge to journey to cross over from North America and then through Indonesia and Australia, or followed the Humboldt Current along the Pacific coast of the Americas. Earlier genetic analyses of some iguanid lizard genes were inconclusive about how the Fiji iguanas are related to those found elsewhere. 'Different relationships have been inferred in these various analyses, none with particularly strong support,' McGuire said. 'So there was still this uncertainty about where Brachylophus really fits within the iguanid phylogeny. Simon's data really nailed this thing.' Scarpetta collected genome-wide sequence DNA from more than 4,000 genes from the tissues of over 200 iguanian specimens from museum collections. The genetic data showed that the Fiji iguanas are most closely related to the iguanas in the genus Dipsosaurus. The most widespread species within the genus is the North American desert iguana, which is adapted to life in the searing heat of the deserts of the American Southwest and northern Mexico. Other species within this genus are native to Santa Catalina Island in the Sea of Cortez. 'Iguanas and desert iguanas, in particular, are resistant to starvation and dehydration, so my thought process is, if there had to be any group of vertebrate or any group of lizard that really could make an 8,000 kilometer [4,970 mile] journey across the Pacific on a mass of vegetation, a desert iguana-like ancestor would be the one,' Scarpetta said. The genetic analysis determined that both lineages–Brachylophus and Dipsosaurus–diverged about 34 million years ago. This revised analysis does not align with the earlier theories of the origin of the Fiji iguanas. [ Related: Pink Iguana hatchlings spotted for the first time on the Galápagos in decades. ] 'When you don't really know where Brachylophus fits at the base of the tree, then where they came from can also be almost anywhere,' McGuire said. 'So it was much easier to imagine that Brachylophus originated from South America, since we already have marine and land iguanas in the Galapagos that almost certainly dispersed to the islands from the mainland.' This new analysis rules out the idea that the iguanas originated in South America. Additionally, because the Fiji Islands themselves emerged from the sea also about 34 million years ago, the iguanas might have landed on the islands just in time not long after. Other Pacific islands aside from Fiji and Tonga may have also harbored iguanas. However, volcanic islands disappear as quickly as they appear, so some evidence of other Pacific Island iguanas may have been lost. The team will continue to analyze genome-wide data for Iguanian lizards to better understand their evolutionary relationships and learn more about their interactions through time and space.
Yahoo
17-03-2025
- Science
- Yahoo
North American iguanas rafted 5,000 miles to colonize Fiji: Study
A subset of North American iguanas likely landed on an isolated group of South Pacific islands about 34 million years ago — having rafted some 5,000 miles from the West Coast of the faraway continent, a new study has found. Their epic journey to what is now Fiji marks the longest known transoceanic expansion of any terrestrial vertebrate species, according to the study, published Monday in the Proceedings of the National Academy of Sciences. Overwater travel for both animals and plants isn't unique in and of itself, as this is the primary way in which newly formed islands have become populated by plants and animals, the study authors noted. Such travel has often led to the evolution of new species and ecosystems — a phenomenon that has fascinated scientists since the time of Charles Darwin. Iguanas themselves are also known for their propensity to float elsewhere and are often found rafting around the Caribbean aboard plant life, the researchers explained. And while the scientists were already aware that the lizards traveled 600 miles to get from Central American to the Galapagos Islands, the massive 5,000-mile trip to Fiji took them by surprise. 'That they reached Fiji directly from North America seems crazy,' senior author Jimmy McGuire, a professor of integrative biology at the University of California, Berkeley said in a statement. 'As soon as land appeared where Fiji now resides, these iguanas may have colonized it,' added McGuire, who is also a herpetology curator at the Museum of Vertebrate Zoology. Previously, biologists had assumed that Fiji iguanas — four species from the genus Brachylophus — descended from an older lineage that was at one point common around the Pacific but ultimately died out. Another possibility was the idea that the lizards 'hitchhiked' from South America and then through Antarctica or Australia. Nonethless, the researchers found there was no genetic or fossil evidence to support those theories. To draw their conclusions, the researchers acquired genome-wide, sequence DNA from more than 4,000 genes and from the tissues of more than 200 iguana specimens in global museum collections. As they began comparing the data to that of the Fiji iguanas, the scientists found that these animals were most closely related to iguanas in the genus Dipsosaurus. Within that genus, the most widespread lizard is the North American desert iguana, Dipsosaurus dorsalis, which has adapted to the desert heat of the U.S. Southwest and Northern Mexico, according to the study. 'If there had to be any group of vertebrate or any group of lizard that really could make an 8,000 kilometer journey across the Pacific on a mass of vegetation, a desert iguana-like ancestor would be the one,' lead author Simon Scarpetta, a former postdoctoral fellow at UC Berkeley. The findings also indicated a much more recent emergence on Fiji — up to 34 million years ago — than the previously suggested arrival times of either 43 million years ago or up to 60 million years ago. 'The lineage of Fiji iguanas split from their sister lineage relatively recently, much closer to 30 million years ago,' added Scarpetta, who is now an assistant professor in environmental science at University of San Francisco. That appearance in Fiji would have either postdated or occurred 'at about the same time that there was volcanic activity that could have produced land,' Scarpetta said. The four species of Fiji iguanas, which inhabit both Fiji and Tonga, are listed as endangered — due to habitat loss, predation by invasive rats and smuggling for exotic pet trades, the authors noted. McGuire acknowledged it may have been 'easier to imagine that Brachylophus originated from South America,' since marine and land iguanas dispersed to the Galapagos from the mainland. But this theory can now be ruled out, he and his colleagues confirmed. Although the scientists could not pinpoint the exact moment and circumstances under which the iguanas arrived in Fiji, they marveled at the prospect of the journey. 'Regardless of the actual timing of dispersal, the event itself was spectacular,' McGuire added. Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
New York Times
17-03-2025
- Science
- New York Times
These Iguanas Got Carried Away and Ended Up 5,000 Miles From Home
For decades, the native iguanas of Fiji and Tonga have presented an evolutionary mystery. Every other living iguana species dwells in the Americas, from the Southwestern United States to the Caribbean and parts of South America. So how could a handful of reptilian transplants have ended up on two islands in the South Pacific, over 4,970 miles away? 'The question has definitely captured the imagination of scientists and the public alike,' said Simon G. Scarpetta, an evolutionary biologist at the University of San Francisco. In research published Monday in the Proceedings of the National Academy of Sciences, Dr. Scarpetta and his colleagues make the case that the ancestors of Fiji's iguanas crossed on mats of floating vegetation. Such a voyage across nearly 5,000 miles of open ocean would be the longest known by a nonhuman vertebrate. Rafting — the term scientists use for hitching a ride across oceans on uprooted trees or tangles of plants — has long been recognized as a way for small creatures on land to reach islands, said Hamish G. Spencer, an evolutionary geneticist at the University of Otago in New Zealand who was not involved in the study. Usually those are invertebrates, whose small size means they can survive a long way in an uprooted tree trunk. While examples from nonflying vertebrates are relatively rare, he added, lizards and snakes seem to be able to raft farther than mammals, perhaps because their slower metabolism allows them to fast for a long time. Iguana species have proved adept at making shorter crossings. In 1995, Dr. Scarpetta said, scientists observed at least 15 green iguanas rafting nearly 200 miles on hurricane debris from one Caribbean island to another. And researchers have long agreed that the ancestors of the iguanas of the Galápagos Islands made the nearly 600-mile trip from South America on bobbing vegetation. A crossing to Fiji, however, represents an almost unimaginable challenge. While some researchers suggested that the Fiji iguana's ancestors had rafted there as well, Dr. Spencer said, others pointed to the vast distances as a reason for skepticism. They countered that the iguanas were the remnant of an extinct group, one that had possibly crossed over land from the Americas to Asia or Australia, and then made the relatively easier crossing to Fiji and Tonga. Dr. Scarpetta's team tackled the question by trying to work out when Fijian iguana species — which belong to a distinct genus, Brachylophus — split off from their closest relatives. After the team sampled the genetics from 14 living iguana species belonging to eight genuses, its analysis suggested that the Fijian species' closest living relatives were the genus Dipsosaurus, a group of desert iguanas found in the American Southwest and northwestern Mexico. 'Compared to other iguanas, both are relatively slender in body shape,' Dr. Scarpetta said, 'and they have some skeletal similarities as well, such as the morphology of their teeth.' The team's analysis suggested that the two genuses split around 30 million and 34 million years ago. That timing is important for a number of reasons, Dr. Scarpetta said: First, it's around the time volcanoes birthed the Fijian archipelago. Second, the cold and ice around the poles at that time would have made it impossible for any lineage of temperature-sensitive iguanas to make it to Asia or Australia from the Americas, and then hop to the Pacific islands. There is also no iguana fossil evidence anywhere in the Eastern Hemisphere other than Fiji or Tonga. 'North America is the most probable area of origin for iguanas in Fiji, and overwater rafting is the best supported mechanism,' Dr. Scarpetta said. The team also argues that the ancestral desert iguanas — tolerant of heat and harsh conditions — would have been well suited for the trip. A three- to four-month crossing would have been roughly the length of Dipsosaurus's winter hibernation, meaning the lizards could have made the voyage without starving. And if the herbivorous reptiles rafted on a mat of vegetation, Dr. Scarpetta added, 'the voyaging iguanas may even have had food on the journey.' Dr. Spencer said, 'In the past, such long-distance dispersal events appeared to be untestable stories, limited only by one's imagination.' But while the suggestion might seem extraordinary, he said, the team makes a very convincing case. After all, the other possible origins for the Fijan iguanas would require events that might have been as unlikely or even more so, such as the extinction and utter disappearance of other iguanas along the alternative routes. The study adds to a growing body of research, Dr. Spencer added, suggesting that 'long-distance dispersal is far more important in the evolutionary history of many animal groups than had previously been appreciated.'
The Hill
17-03-2025
- Science
- The Hill
North American iguanas rafted 5,000 miles to colonize Fiji: Study
A subset of North American iguanas likely landed on an isolated group of South Pacific islands about 34 million years ago — having rafted some 5,000 miles from the West Coast of the faraway continent, a new study has found. Their epic journey to what is now Fiji marks the longest known transoceanic expansion of any terrestrial vertebrate species, according to the study, published on Monday in the Proceedings of the National Academy of Sciences. Overwater travel for both animals and plants isn't unique in and of itself, as this is the primary way in which newly formed islands have become populated by plants and animals, the study authors noted. Such travel has often led to the evolution of new species and ecosystems — a phenomenon that has fascinated scientists since the time of Charles Darwin. Iguanas themselves are also known for their propensity to float elsewhere and are often found rafting around the Caribbean aboard plant life, the researchers explained. And while the scientists were already aware that the lizards traveled 600 miles to get from Central American to the Galapagos Islands, the massive 5,000-mile trip to Fiji took them by surprise. 'That they reached Fiji directly from North America seems crazy,' senior author Jimmy McGuire, a professor of integrative biology at the University of California Berkeley, said in a statement. 'As soon as land appeared where Fiji now resides, these iguanas may have colonized it,' added McGuire, who is also a herpetology curator at the Museum of Vertebrate Zoology. Previously, biologists had assumed that Fiji iguanas — four species from the genus Brachylophus — descended from an older lineage that was at one point common around the Pacific but ultimately died out. Another possibility was the idea that the lizards 'hitchhiked' from South America and then through Antarctica or Australia. Nonethless, the researchers found that there was no genetic or fossil evidence to support those theories. To draw their conclusions, the researchers acquired genome-wide, sequence DNA from more than 4,000 genes and from the tissues of more than 200 iguana specimens in global museum collections. As they began comparing the data to that of the Fiji iguanas, the scientists found that these animals were most closely related to iguanas in the genus Dipsosaurus. Within that genus, the most widespread lizard is the North American desert iguana, Dipsosaurus dorsalis, which has adapted to the desert heat of the U.S. Southwest and Northern Mexico, according to the study. 'If there had to be any group of vertebrate or any group of lizard that really could make an 8,000 kilometer journey across the Pacific on a mass of vegetation, a desert iguana-like ancestor would be the one,' lead author Simon Scarpetta, a former postdoctoral fellow at UC Berkeley. The findings also indicated a much more recent emergence on Fiji — up to 34 million years ago — than the previously suggested arrival times of either 43 million years ago or up to 60 million years ago. 'The lineage of Fiji iguanas split from their sister lineage relatively recently, much closer to 30 million years ago,' added Scarpetta, who is now an assistant professor in environmental science at University of San Francisco. That appearance in Fiji would have either post-dated or occurred 'at about the same time that there was volcanic activity that could have produced land,' Scarpetta said. The four species of Fiji iguanas, which inhabit both Fiji and Tonga, are listed as endangered — due to habitat loss, predation by invasive rats and smuggling for exotic pet trades, the authors noted. McGuire acknowledged that it may have been 'easier to imagine that Brachylophus originated from South America,' since marine and land iguanas dispersed to the Galapagos from the mainland. But this theory can now be ruled out, he and his colleagues confirmed. Although the scientists might could not pinpoint the exact moment and circumstances under which the iguanas arrived in Fiji, they marveled at the prospect of the journey. 'Regardless of the actual timing of dispersal, the event itself was spectacular,' McGuire added.
