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Snakes had an evolutionary explosion after dinosaur extinction

A new study reveals that snakes experienced a magnificent burst of evolution from unassuming insectivorous ancestors to diverse genealogies after the demise of dinosaurs. The new families of reptiles that evolved incorporated newly available birds, fish, and small mammals in their diets. 

Snake diversification was similar to the extraordinary diversification of mammals and birds that occurred after the extinction of dinosaurs 66 million years ago, according to research by Michael Grundler of UCLA and Daniel Rabosky of the University of Michigan.

The experts report that the extinction of non-avian dinosaurs combined with the long-term physiographic changes created new habitats that provided an ecological opportunity for various species to evolve and diversify.

The K-Pg mass extinction event occurred 66 million years ago and resulted in the extinction of 75 percent of all species, including all non-avian dinosaurs. The event heralded the start of the Cenozoic period and created a plethora of unfilled niches for the remaining species to exploit. Snakes, like mammals and birds, diversified fast during the Cenozoic era, ultimately yielding around 4,000 species that live today.

The study authors combined primary natural history observations with stochastic model-based comparative methods to explain the evolution of complex ecological phenotypes. The researchers compiled published data on the diets of 882 surviving snake species and employed advanced mathematical models to reconstruct how their ancestors’ diets altered and diversified since the K-Pg boundary. The models helped the researchers in understanding the pace and sequence of this phenomenon. 

The experts discovered that the most recent common ancestor of surviving snakes was an insectivore. However, following the K-Pg boundary, the snakes modified their diets rapidly to include birds, fish, and small mammals – vertebrate taxa that were also prospering in the aftermath of dinosaur extinction.

The research investigated the explosive adaptive radiation that resulted in creating the snake diversity we witness today. After the first radiation,  diet diversification in snakes decreased, but some lineages underwent additional bursts of adaptive evolution. For example, Colubroid snakes diversified when Old World ancestors colonized North and South America.

According to the scientists, the findings from the study suggest that major extinctions and new biogeographic opportunities can stimulate evolutionary change. 

“Much of the stunning ecological diversity in snakes seems to result from evolutionary explosions triggered by ecological opportunity,” said Grundler. “We find a major burst of snake diet diversification after the dinosaur extinction, and we also find that, when snakes arrive in new places, they often undergo similar bursts of dietary diversification,” he added.

The study is published in the journal PLOS Biology

By Ashikha Raoof, Staff Writer

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