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DNA can help predict ecosystem changes when animals are reintroduced

A new technique developed by researchers at Stanford University can be used to forecast ecosystem changes that will occur when certain species vanish or become more prevalent. The study is the first of its kind to track various species’ interactions across a terrestrial ecosystem by analyzing DNA samples from animal feces. 

In 1995, wolves were reintroduced to Yellowstone National Park. As a result, the ecosystems across the region were completely transformed through cascading effects on other animals and plants.

The Stanford team has designed a low-cost tracking technique that could help inform conservation efforts and allow experts to anticipate the ecosystem changes that will take place when locally extinct species are reintroduced.

“It’s not just that we can rapidly capture the biodiversity of an area,” said study study lead author Dr. Jordana Meyer. “We can also quantify the extent of indirect links among species, such as how a specific predator’s behavior affects vegetation in an area. This allows us to measure impacts on species that are essential to the system or particularly vulnerable.”

The disappearance of animals can be as transformative as the introduction of species, and the ripple effects are difficult to predict. Dr. Meyer has witnessed these types of impacts firsthand in the Democratic Republic of Congo, where the absence of rhinos and elephants has shrunk the grassland savannas that the large herbivores once grazed

Across Stanford’s 1,193-acre Jasper Ridge Biological Preserve, the researchers analyzed feces from carnivores, omnivores, and herbivores such as mountain lions, gray foxes, and black-tailed deer.

Based on the DNA, the experts identified the diets of these animals and constructed a detailed, data-rich food web. They also captured the biodiversity of the area more quickly and reliably than other animal surveys, including a long-term camera trap study in the preserve.

The analysis revealed the indirect effects of predatory behavior on vegetation, as well as other ecosystem changes. The results were validated against evidence from camera trap data that has been collected in Jasper Ridge over the past seven years. 

The research showed that the return of mountain lions, the ecosystem’s top predator, caused a decline in the abundance of deer and coyotes. Without the coyote as a competitor, the formerly rare gray fox returned to Jasper Ridge. 

Compared to coyotes, gray foxes consume and redistribute more fruit and seeds. Ultimately, the prevalence of the gray fox was directly tied to the abundance of fruit plants in Jasper Ridge. Understanding these relationships can help conservation managers anticipate the impacts of shifting animal and plant communities.

The DNA that was collected in animal feces also revealed the presence of plant and animal species that were not known to occur within the preserve, providing an early warning of invasive species.

“We are excited about this approach because it will not only help us to understand how and why species survive in protected areas based on what they eat, but also whether animals are able to capitalize on non-native plant and animal species,” said study senior author Professor Elizabeth Hadly. 

According to Dr. Meyer, the researchers plan to scale-up their model across protected areas in Africa to assist in strategic adaptive management and rewilding strategies. “I am hopeful that techniques like this can help us secure and monitor natural spaces on a global scale.”

The study is published in the journal Frontiers in Ecology and Evolution.

By Chrissy Sexton, Staff Writer

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