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CALIFORNIA, U.S., CMC – Scientists in the United States say the study of Caribbean lizards reveals that evolution is predictable.
According to a study of Caribbean lizards by researchers at the University of California at Davis (UC Davis), Harvard University and the University of Massachusetts and published in the journal, “Science” if you could hit the reset button on evolution and start over, the same species would essentially appear.
“The predictability of evolution over timescales of millions of years has long been debated by biologists,” says Luke Mahler, a postdoctoral fellow at UC Davis and first author on the paper.
For example, he says the late scientist Stephen Jay Gould predicted that if you “rewound the tape” on evolution and started over, you would get an entirely different outcome, arguing that small events, such as a storm that wiped out a particular pond and a poor season for insects, could have a disproportionate effect.
On the other hand, Mahler says there are a number of examples of species in similar habitats that evolve independently into similar-looking forms, such as the cichlid fishes of African lakes.
“It’s a big question in evolutionary biology, but very hard to test,” Mahler said, noting that he found his test subjects in the Anole lizards that live on four islands, namely Cuba, Hispaniola, Jamaica and Puerto Rico.
Mahler says anoles began colonizing these islands, all similar in climate and ecology, about 40 million years ago, and once there, they began to multiply, resulting in a diversity of species on each.
The researchers say they studied 100 of the 119 Anole lizard species from the islands, taking measurements of their bodies from wild and museum specimens and comparing them across islands.
They say they found a striking degree of convergence, stating that, on each island, evolution had produced a set of very similar-looking lizards occupying similar environmental niches.
“The adaptive radiations match on all four islands, with few exceptions, each species on an island has a match on the other islands,” Mahler says.
By combining the body-form data with a family tree of the Anoles, Mahler says he and his colleagues were able to construct an “adaptive landscape” for the lizards.
Mahler said an adaptive landscape is a fundamental concept in evolutionary biology but difficult to show in practice, and that peaks on an adaptive landscape represent various combinations of features that will be favored by natural selection, whereas valleys are just the opposite. Species with similar habits will tend to cluster on the same peak.
