This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A new study has found that adaptive molecular convergence—the process by which distantly related or unrelated species evolve the same genomic changes—is not as rare as previously thought. By reconstructing and studying sections of jellyfish genomes from the deep past, researchers found evidence of identical genetic changes in multiple lineages separated by more than 600 million years.
The work was conducted by researchers at the University of California, Santa Barbara, the University of Kansas, Texas A&M University and the University of Nebraska. "We're studying molecular evolution here—to what extent similar genetic changes occur in different organisms," said Cory Berger, a postdoctoral researcher in the lab of UCSB biologist Todd Oakley. "And that in particular is something we don't know much about." According to the paper, these identical genetic changes were largely unassociated with the jellyfishes' phenotypic convergence, or the evolution of similar physical traits in distantly related species, suggesting a complex relationship between genetic and phenotypic convergence.
The research is published in the Proceedings of the National Academy of Sciences. How repeatable is evolution, and under what time scales and circumstances is it repeatable? This was the core question of the research, said Oakley, the paper's senior author.
Answering this question would provide insight into the predictability of evolution, he added, which could help researchers predict evolutionary outcomes, including how genes underlie physical traits. To investigate, the researchers turned to Medusozoa, an ancient and diverse lineage that includes jellyfish and their relatives. Emerging about 650 million years ago, this clade includes members that have undergone convergent and repeated phenotypic evolution, including multiple origins of eyes and repeated losses of the free-swimming medusa stage.
"We're studying this particularly old group of animals that has some interesting convergent phenotypes that we already know about," Berger said. The idea was to associate patterns of molecular convergence found in the jellyfish genomes with the convergent phenotypes. "Maybe it's just the case that organisms that have phenotypic convergence who look similar to one another have convergent molecular changes." But first, the researchers needed to reconstruct Medusozoa's evolutionary history.
With fossil and molecular data, they created an evolutionary tree, using a method called ancestral state reconstruction, to infer the convergent emergence of certain traits like eyes. It's one of the most comprehensive jellyfish phylogenetic trees to date. The researchers then examined the genetic data.
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