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Scientists develop models to evaluate amphibian biodiversity

February 26, 2020

These days, a lot of people are vying for territory in the nation’s capital, but you may be surprised to know that since 2005, the National Capital Region Network (NCRN) of 11 national parks in and around Washington, D.C. has been paying very close attention to the thin-skinned constituents who also live and breathe there—amphibians.

Frogs, toads, salamanders and newts breathe and absorb water through their skin, making them key vital signs of a healthy park, but for the past 10-15 years, these vital signs have been declining.

Two researchers in MSU’s Department of Integrative Biology and the Ecology, Evolution, and Behavior Program – Elise Zipkin, assistant professor, and Alex Wright, fourth year Ph.D. student – are developing statistical models to understand why.

In a recently published paper in Landscape Ecology, Wright and Zipkin, along with Evan Grant, director of the U.S. Geological Survey’s Northeast Amphibian Research and Monitoring Initiative, integrated amphibian biodiversity data across spatial scales into a statistical analysis to evaluate the factors influencing amphibian communities and inform management decisions across the NCRN.

“Models like this can help us evaluate species trends through time as well as the specific factors that influence their distributions across space,” said Zipkin, lead investigator of the Zipkin Quantitative Ecology Lab.

Image of adult green frog
An adult green frog, Lithobated clamitans, perched on a branch floating on the surface of a wetland.  Photo credit: USGS/C. Shafer

The team used the natural fragmentation of the NCRN as a case study to understand how scale mediates relationships between biodiversity and landscape variables such as connectivity between parks, habitat quality and the total area of a park.

“Amphibians are indicators of biological integrity, so when they decline, we know there is a larger problem with the ecosystem—whether that is driven by urbanization, climate change or other drivers,” said Wright, who has participated in data collection at the NCRN parks every summer for the past four years. “We also know from almost 15 years of monitoring in the NCRN that habitat fragmentation is occurring in this very urban region, but there is a lot of conflict in the scientific literature about the effect of fragmentation on species richness.”

With some amphibians active earlier in the year, like the spotted salamander, and some later, like the spring peeper, determining species richness with accuracy is tricky, but the team’s model was able to account for all species and parks across the NCRN, even estimating the number of species that were unobserved during data collection.

“Even though detection and wetland occupancy rates varied across species, our community occupancy model allowed us to estimate trends for both common and rare species across the network of parks,” Wright explained. “Being able to analyze these data at a large scale and to understand spatial variation among parks is a novel statistical advancement.”

Read more at NatSci and MSU Today.