Summit County Citizens Voice

Water shrews are native to northern Rockies and parts of the Pacific Northwest. Photo courtesy USFWS.

Studies of small mammals could help inform wildlife management in the face of climate change

By Summit Voice

SUMMIT COUNTY — U.S. Geological Survey scientists say various species of shrews in the Arctic have evolved rapidly in response to past climate changes, making them good test subjects to project how current climate change scenarios might play out.

Since the tiny mammals breed quickly and don’t migrate, they illustrate how species might change in response to global warming, showing both ecological and evolutionary responses to local conditions year-round.

“Evolutionary adaptation is driven by necessity, favored by large gene pools, and accelerated by short intervals to reproductive maturity,” USGS Director Marcia McNutt said, discussing findings in a recent USGS study.

“All of these factors make shrews the ideal organism for examining genetic adaptation to climate change, understanding which is critical to helping manage wildlife in the decades ahead,” she said.

Shrews rely on insects, worms and other invertebrates for food. Despite their diminutive size, they can be found in virtually every available terrestrial habitat in North America excluding the most arid desert regions, reflecting adaptation to a broad range of environmental conditions.

The researchers used historical climate data and modern molecular evidence from multiple genes, to determine that some shrew species respond positively to periods of warmer and wetter climate through expanding geographic ranges and increased population sizes. Other shrew species respond the same way during periods of colder and drier climate.

Climatic changes over the last 350,000  years have caused dramatic environmental shifts at high latitudes. For example, glacial cold phases lasting approximately 75 thousand years were interspersed with warmer periods lasting 20 thousand years and the earth is now experiencing yet another of these warmer periods.

“Our research suggests that early ancestors of this group of roughly a dozen shrew species experienced an ecological separation due to isolation in different areas, adapting to wetter or drier local conditions respectively,” said Dr. Andrew Hope, a geneticist with the USGS Alaska Science Center who led the research.

Following initial adaptation to different environments, each cold and dry glacial phase caused rapid expansion of one group of shrew species while those adapted to warmer and wetter conditions contracted into multiple small isolated areas.

Then during each warm and wet interglacial phase the opposite dynamics occurred. As high-latitude climates alternated between warm and cold climate changes, species such as the shrews rode an evolutionary see-saw of alternating population growth and decline, which promoted the formation of new species.

The result has been a rapid increase in number of species in the Arctic in a very short evolutionary timespan. Investigation of these shrews has also uncovered previously unrecognized genetic diversity possibly representing un-described species.

The article “A climate for speciation: Rapid spatial diversification within the Sorex cinereus complex of shrews” is published in the journal Molecular Phylogenetics and Evolution, written by Andrew Hope and Sandra Talbot of the USGS Alaska Science Center, Joseph Cook and Kelly Speer from the Museum of Southwestern Biology at the University of New Mexico and John Demboski from the Denver Museum of Nature & Science.

Filed under: climate and weather, Environment, global warming Tagged: | adaptation, Arctic, climate, climate change, evolution, global warming, USGS