How Biodiversity Arises: Fish Skulls Shed Light on Evolution with Gene Mutation

It turns out that a single gene mutation could explain exactly how biodiversity arises. Scientists have discovered that this mutation can lead to different consequences not only in how animals' skull and jaw are shaped, but could also lead to different feeding strategies that allow animals to exploit different ecological niches.

Until now, the field of evolutionary developmental biology has mostly focused on connecting gene-level changes with the evolution of different anatomical shapes, or morphology. Yet scientists have been less successful in revealing how these anatomical changes influence how an organism performs in a specific environment.

"It is not the shape of an organism that determines fitness, per se," said Craig Albertson, one of the researchers, in a news release. "Rather, it is how an organism interfaces with its environment that determines its survival. Shape tells part of this story, but function gets you a lot closer to understanding how well suited an animal is to its surroundings."

In order to better understand the process of evolution, the scientists took a look at the cichlid fish. More specifically, they combined traditional genetic mapping and experimental embryology to show how changes in the ptch1 ("patch1") gene, a member of the hedgehog signaling pathway, alter skull and jaw development in the fish, leading to pronounced shape changes as an adult.

"One form of the gene helps to produce faster moving jaws that are better able to collect highly mobile prey," said Yinan Hu, one of the researchers, in a news release. "The alternate form leads to the development of jaws that are slower but more powerful, which is better for consuming hard prey. It accomplishes this by altering many bones in the head at once. In other words, these simple genetic variants should go a long way toward allowing organisms to carve out different ecological niches."

In the end, the researchers found that the effects of different ptch1 variants on jaw development may help explain how this group of fish has managed to evolve so many species in such a brief period of time. Because a single genetic change drastically impacts several skeletal elements, the fish managed to evolve different feeding strategies and take advantage of different ecological niches.

"Natural selection doesn't need to coordinate changes at multiple places in the genome to enable a species to adapt to a new environment," said Albertson in a news release. "A small number of changes is likely sufficient to enable competing species to carve out different niches, enabling their coexistence."

The findings are published in the journal Nature Communications.