Reef fish on a narrow diet evolve faster, study finds

Reef fish evolve faster and have greater genetic diversity when they have less food to choose from, according to researchers from Monash University and the USA.

The team found that fish at the top or bottom of the food-web, who have less variety in their diet, evolve faster than fish in the middle of the food-web.

The findings are from a collaborative study between Monash University and the University of Tennessee, which has produced the first large-scale diet study in coral reef fishes.

The study, published today in Nature Ecology and Evolution, shows that fish species at the top of the food chain evolve into more diverse forms more quickly than other fish species.

Monash researcher Dr Matthew McGee with his fish. Image credit: Steve Morton

“Understanding how these systems evolve is critical for informing successful conservation measures on coral reefs,” said senior study author Dr Matthew McGee, who heads the Fish Biodiversity Group at Monash University.

The researchers produced an evolutionary ‘family tree’ describing the relationships of over 1500 coral reef species. Over 50 percent of these fish are known to occur on the Great Barrier Reef.

They then added information on each species’ diet, as well as key traits like body size, mouth size, and body shape.

They found that species specialised to feed exclusively on other fish, like coral trout, longtom, and frogfish, evolved at a much faster rate than species with broader diets.

The prevailing theory was that species that ate a wide variety of different foods might evolve more quickly, but the researchers showed that the exact opposite pattern occurred.

Dr McGee said that the more limited focus of previous studies may have contributed to this.

“By combining information from many fish groups, we were able to see that studying a single group at a time, as researchers have done in the past, was not enough to understand the broad-scale patterns across reef fishes,” Dr McGee said.

“Unfortunately, many of the species evolving the fastest are also commercially exploited,” he said.

“Coral reef predators, like coral trout, are some of the most heavily targeted species on reefs. Our research suggests that overfishing has the potential to dramatically reduce the functional diversity of reef fishes.”

For further information, or to arrange an interview with Dr McGee, contact:

Silvia Dropulich Marketing, Media and Communications Manager, Science

T: +61 3 9902 4513 M: +61 (0) 0435138743 E: silvia.dropulich@monash.edu