Harvard researchers find rapid evolution of reptiles triggered by nearly 60 million years of global warming and climate change
HARVARD UNIVERSITY, ORGANIC BIOLOGY AND EVOLUTION
Studying mass extinctions caused by climate change in the deep geological past allows researchers to explore the impact of environmental crises on the evolution of organisms. A major example is the Permian-Triassic climate crises, a series of climate changes due to global warming that occurred between the Middle Permian (265 million years ago) and the Middle Triassic (230 million years ago). before). These climate changes caused the two largest mass extinctions in the history of life at the end of the Permian period, the first at 261myo and the other at 252myo, which subsequently eliminated 86% of all animal species. objects worldwide.
The late Permian extinctions are important not only because of their magnitude but also because they marked the beginning of a new era in planetary history when reptiles became the dominant group of vertebrates living on shallow. During the Permian, terrestrial vertebrates were dominated by synapses, the ancestors of mammals. After the extinction of the Permian, in the Triassic (252-200 million years ago), reptiles evolved at a rapid rate, creating an explosion in reptile diversity. This expansion is key to the construction of modern ecosystems, and many are extinct. This rapid rate of evolution and diversification is believed by most paleontologists to be due to the extinction of competitors that allowed reptiles to take over new habitats and food sources. several synapsid groups dominated before they became extinct.
However, in a new study in Scientific advance Researchers at the Department of Evolutionary Biology and Biology and the Museum of Comparative Zoology at Harvard University and collaborators reveal that the rapid and radiation evolution of reptiles began earlier. much, prior to the end of the Permian, is associated with a steady rise in global temperatures over an extended period of a series of climate changes spanning nearly 60 million years in the geological record.
“We found that these rapid stages of reptile evolution are strongly associated with increasing temperatures. Some groups change very quickly and a few are faster, but nearly all reptiles evolved much faster than before,” said Tiago R Simões, lead author of the study.
Previous studies on the effects of these changes often overlooked terrestrial vertebrates due to limited data sources, mainly focusing on marine animal responses.
For this study, Simões and senior author, Professor Stephanie E. Pierce (both at Harvard) worked with collaborators Professor Michael Caldwell (University of Alberta, Canada) and Dr. Christian Kammerer (North Carolina Museum of Natural Sciences) to check for early amniotic fluid. represent the forerunners of all modern mammals, reptiles, birds, and their closest extinct relatives, at an early stage in their evolution. At this time, the first groups of reptiles and mammalian ancestors were diverging from each other and evolving along their separate evolutionary paths.
“Reptiles represent an ideal and rare terrestrial system to study this question because they have a relatively good fossil record and have survived a series of climate crises, including the The crisis resulted in the largest extinction in the history of complex life, the Permian-Triassic mass extinction,” said Simões.
Reptiles were relatively rare during the Permian period compared with their mammalian ancestors. However, things took a big turn during the Triassic period when reptiles experienced a huge explosion in species numbers and morphological diversity. This led to the emergence of most of the major groups of living reptiles (crocodilians, lizards, turtles) and some that are now completely extinct.
The researchers created a dataset based on an extensive first-hand data collection of more than 1,000 fossil samples from 125 reptiles, synapses, and their closest relatives from about 140 million years ago. and after the Permian-Triassic extinction event. They then analyzed the data to discover when these species first originated and how fast they evolved using modern analytical techniques such as Bayesian evolutionary analysis, which is also used. to understand the evolution of viruses like SARS-COVID 19 The researchers then combined the new data set with global temperature data spanning several million years in the geological record to provide a glimpse overview of the main adaptive responses of animals to climate change.
“Our results suggest that periods of rapid climate change and global warming are associated with exceptionally high rates of anatomical change in most groups of reptiles as they prefer to live,” said Pierce. acclimatization to new environmental conditions, and that this process began long before the Permian-Triassic extinction, since at least 270 million years ago, suggests that the plan to diversify reptiles was not stimulated triggered by the PT extinction event as previously thought, which in fact began tens of millions of years earlier”.
“One line of reptiles, the lepidosaurs, gave rise to the first lizards and tuatara, going in the opposite direction of most reptile groups and going through a period of very rapid variability,” says Simões. slow to their overall anatomy,” says Simões, “basically, their body plans are constrained by natural selection, rather than becoming rogue and radically changing like most species. other reptiles at the time”. The researchers attribute this to a pre-adaptation of their body size to better cope with high temperatures.
“The physiology of organisms really depends on their body size,” says Simões. Small-bodied reptiles can better exchange heat with their surroundings. The early lizards and tuatara were much smaller than other groups of reptiles, not much different from their modern relatives, and thus they were better adapted to cope with drastic temperature changes. . The much larger ancestors of crocodiles, turtles and dinosaurs could not lose heat easily and had to rapidly change their bodies to adapt to new environmental conditions.”
Simões, Pierce and collaborators also mapped how body size has changed across geographic regions during this time frame. They revealed that climate pressures on body size were too high for reptiles to have maximum body sizes to survive in the tropics during this time’s deadly heat.
“Large reptiles go two ways to cope with these climate changes,” says Pierce, “either migrating closer to temperate regions or entering aquatic worlds where they do not exist,” says Pierce. need to worry about overheating because water can absorb heat and maintain its temperature much better than air. “
“The close association between temperature increases in the geological past and the biological responses of different groups of reptiles suggests that climate change is a key factor in explaining the origin and outbreak of these outbreaks,” said Simões. explosion of new reptilian body plans in the most recent Permian and Triassic. .
The researchers would like to thank the Museum of Comparative Zoology (MCZ), Harvard University, the vertebrate paleontology staff, and the curators of more than 50 natural history collections worldwide. helped them in accessing the specimen. Funding is provided by: Alexander Agassiz Postdo PhD Fellowship, MCZ; Postdoctoral Fellowships of the National Scientific and Technical Research Council of Canada (NSERC); Grant KA 4133 / 1-1 from Deutsche Forschungsgemeinschaft; NSERC Discovery Grant #23458 and NSERC Accelerator Grant; Faculty of Science, Research Allowance Chair, University of Alberta; Lemann Research Foundation Brazil; The funds are made through Harvard University.
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JOURNEYS
Scientific advance
DOI
ARTICLE TITLE
Successive climate crises in the past spurred the early evolution and radiation of reptiles
ARTICLE PUBLICATION DATE
August 19, 2022
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