Biologists discover new home for evolution of fish

Avatar By Lliane Hunter | 2 years ago

Biologists have compiled the largest evolutionary family tree of fish in the history of the field, writes Emma Betuel for Inverse. The purpose of the study, published in the journal Nature, was to further understand geographical patterns when it comes to how species form. According to lead study author and University of Michigan zoologist, Daniel Rabosky, “the difference in species diversity from the poles to the tropics is one of the ‘big patterns’ in biology.”

The understanding in the field had been that warm, tropical places tend to have far more varieties of species than cold barren ones. However, the new paper disputes this theory, suggesting that it’s actually the coldest places on earth that are hotbeds for new species. After constructing an evolutionary tree of some 30,000 species of fish, Rabosky’s team concluded that, over the past million years, fish living in polar waters formed new species twice as fast than those in tropical waters.

The team started by analyzing the available DNA data from around 5,000 species of fish, and used other placement methods to estimate where the remaining fish should fit in the family tree, Betuel explains. “This tree is much larger than any previous study on fishes,” Rabosky says. “It enabled us to estimate the rates at which species form with much greater accuracy than previous studies.” He isn’t sure why the rate of speciation is faster in the poles, but suggests that it could stem from tough polar conditions  prompting a series of mass extinctions that opened the door for new species to form.