Study Suggest Reptile Ancestors Where Not Strictly Oviparous
Furthermore, the researchers contend, these species have switched back and forth in their preferred reproductive mode over time.
“This is a very unusual and controversial finding, and a major overturn of an accepted school of thought,” said Alex Pyron, an assistant professor of biology at George Washington University. “Before, researchers long assumed that the ancestor of snakes and lizards laid eggs, and that if a species switched to live birth, it never reverted back. We found this wasn’t the case.”
Pyron analysed an evolutionary tree containing all groups of squamates – the group that comprises lizards and snakes – which he and a team of researchers published in the journal BMC Evolutionary Biology earlier this year.
The tree, which uses DNA sequencing technology to group thousands of lizards and snakes, includes all families and subfamilies and most genus and species groups.
In total, about 115 groups of lizards and snakes, or about 2,000 species, have live birth. The other 8,000 species lay eggs – at least right now.
Pyron is working next to analyse all tetrapods – a group comprised of animals with four legs, such as amphibians, reptiles, birds, mammals and turtles – to see if there are any new surprises about the evolution of their reproductive modes.
He also wants to test the genetics at work behind the evolutionary switching of reproductive mode.