WASHINGTON - A new research by scientists has named mammals and many species of birds and fish as evolution’s “winners”, while crocodiles, alligators and a reptile cousin of snakes known as the tuatara are among the “losers”.
“Our results indicate that mammals are special,” said Michael Alfaro, a UCLA (University of California, Los Angeles) assistant professor of ecology and evolutionary biology and lead author of the research.
Alfaro and his colleagues analyzed DNA sequences and fossils from 47 major vertebrate groups and used a computational approach to calculate whether the “species richness” of each group was exceptionally high or low.
The research allows scientists to calculate for the first time which animal lineages have exceptional rates of success.
Among the evolutionary winners are most modern birds, including the songbirds, parrots, doves, eagles, hummingbirds and pigeons; a group that includes most mammals; and a group of fish that includes most of the fish that live on coral reefs, according to Alfaro.
A group with the scientific name Boreoeutheria, which consists of many mammals, has diversified about seven times faster than scientists would have expected, beginning about 110 million years ago, Alfaro and his colleagues calculated.
The group includes primates and carnivores, as well as bats and rodents. Pouched mammals, such as kangaroos, are not as richly varied as other mammals.
“Modern birds have diversified about nine times faster than expected, starting about 103 million years ago, and the group of fish that live on coral reefs has diversified about eight times faster than expected,” said Alfaro.
Crocodiles and alligators are nearly 250 million years old yet have diversified into only 23 species, according to Alfaro.
They are diversifying a staggering 1,000 times slower than would have been expected.
“Their species richness is so low, given how old they are,” said Alfaro.
The tuatara, which lives in New Zealand and resembles lizards has only two species.
“In the same period of time that produced more than 8,000 species of snakes and lizards, there were only two species of tuatara,” Alfaro said.
“Why these evolutionary losers are still around is a very hard thing to explain. They have been drawing inside straights for hundreds of millions of years. It’s a real mystery to biologists how there can be any tuataras, given their low rate of speciation. They must have something working for them that has allowed them to persist,” he added. (ANI)