Most terrestrial plants and animals left the ocean a single time in their evolutionary history to live ashore. But crabs have seemingly scuttled out of the sea more than a dozen times, with at least two groups later reverting back to a marine lifestyle, a study finds.
Unlike for well-studied animals such as birds and mammals, a unified crab tree of life has been lacking, says Kristin Hultgren, an invertebrate zoologist at Seattle University. “While the authors have developed a useful framework for understanding the complexity of transitioning to terrestrial life, one of the most important contributions is the extensive, well-dated evolutionary tree.”
Crabs are an extremely diverse group and have colonized nearly every type of habitat on Earth. It’s been a challenge to study when crabs first shifted from one habitat to another during evolution because, like some other invertebrates, crabs don’t have the extensive fossil trail that early vertebrates do, says Joanna Wolfe, an evolutionary biologist at Harvard University.
Past research has also often treated marine, freshwater and land crabs as discrete subgroups when they’re more like a continuum, Wolfe says. “They’re not distinct and actually have a lot in common, and looking at them together helps trace their evolution.”
2023-11-20 10:00:00
Source from www.sciencenews.org
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