A ‘blind spot’ in species formation contradicts Darwin

3 Jan. () –

Most species evolve adapting to similar large-scale environmental pressuresaccording to a study that contradicts Darwin’s theories.

Evolutionary biologists have traditionally believed that most new species form because they have adapted to different environments.

But a new study from the University of Toronto, published in Science magazinesheds light on what researchers have called a “blind spot” in our understanding of why new species form.

“We found that species actually adapt systematically to similar environmental pressures,” he says. it’s a statement Sean Anderson co-authored the paper with Professor Jason Weir while earning his PhD at the University of Toronto Scarborough. “They are undergoing the classic Darwinian adaptation, but they don’t do it in very different environments.”

Although it is generally accepted that populations must be separated physically to begin to evolve into new species, the researchers say that what happens during that isolation has been murky. For decades, the prevailing theory has been ecological speciation, that is, groups evolve because they migrate to different environments and experience pressures not faced by the rest of their species, be it new food sources or predators. Environmental features, called divergent adaptation, drive natural selection that results in the formation of a new species. Darwin’s finches, which evolved beaks more suitable for seeds than insects, are one example.

But it is also common to see species that have evolved to the point that they can no longer reproduce with their closest relatives, even though they still share most traits with their peers. This made the researchers think that the environments in which evolution took place, while geographically distant, might not have been so different. This is an established but less accepted explanation, known as parallel adaptation.

“Insights about divergent adaptation have been largely dominated by the study of model organisms, that is, species with large ecological differences,” Anderson explains. “We wanted to see what patterns we could find by studying as many species as possible.”

The researchers used the largest and most extensive data set ever assembled on the divergent traits of species and their closest relatives, sister pairs. They also created a statistical model that allows, for the first time, to estimate whether a species evolved with a parallel or divergent adaptation. In nearly 3,000 sister pairs of birds, mammals, and amphibians, species evolved for the most part under similar large-scale environmental pressures.

“We found that parallel adaptation seems to dominate, and no matter what traits you look at, it’s the same in almost every pairing group of species,” says Anderson, who is now doing postdoctoral research at the University of Carolina. North on Chapel Hill. “We were surprised at how consistent this signing was.”