Warmer Temperatures Expedite Hybrid Trout Takeover

When two species mate, their offspring end up with new names like ‘pizzly’ (a grizzly and polar bear pairing) or ‘sparred owl’ (for barred owl and spotted owl hybrids). According to a June High Country News article, the more rare species in such couplings face a far worse fate--hybridization can be a path to extinction. That’s why hybridization is a major concern for conservationists of the West’s 12 cutthroat trout species. For over a century, rainbow trout native to the Pacific Coast have been enthusiastically planted throughout the U.S., plus every continent besides Antarctica, for sport fishing. In the West, they interbreed with their ruby-jawed cousins to form “cuttbow” hybrids. Those offspring are often not as fit to survive and reproduce. And it turns out that our warming climate (and resulting warmer water temperatures) is setting the stage for these less adaptable mutts to prosper. In a new study in the journal Nature Climate Change, a research group led by Clint Muhlfeld, an aquatic ecologist with the U.S. Geological Survey in Glacier National Park, connected warmer temperatures and decreased precipitation to accelerated hybridization of rainbow trout and the Northern Rocky’s Westslope cutthroat trout. Though scientists have long predicted that climate change will increase opportunities for species to hybridize, the new research results are the first to show it.