An extensive genomic study led by Canadian and U.S. scientific institutions confirms hybridization between polar bears (Ursus maritimus) and grizzly bears (Ursus arctos horribilis) is exceptionally rare in nature. Despite growing speculation of increasing hybrids due to climate change, researchers found only the eight known crosses, debunking recent alarmism and redefining Arctic conservation priorities.

Genetics Debunks Hybrid Proliferation

Published June 13, 2024, in Conservation Genetics Resources, the research used a new genotyping chip—the Ursus maritimus V2 SNP—analyzing over 8,000 genetic markers with high precision in polar/grizzly bear samples. The study examined DNA from 371 polar bears and 440 grizzlies collected in Canada, Alaska, and Greenland (1975-2015).

Contrary to assumptions of rising hybridization, no new hybrids emerged beyond eight registered—all from female polar bear x male grizzly crosses. That’s under 1% of 819 samples. Environment and Climate Change Canada’s Evan Richardson stated: “Contemporary hybridization is restricted to a small western Arctic bear group and poses no significant current conservation concern.”

Research clarifies past gene flow existed (polar bears evolved from grizzlies hundreds of thousands years ago), but recent hybrids remain extremely limited, geographically confined, rare even where habitats overlap.

Grolars and Pizzlies: Genetic Rarity, Little Adaptive Value

Hybrids—popularly grolars or pizzlies (male parent-dependent)—are all grolars: female polar x male grizzly. Detected only where populations overlap, excluding high Arctic.

While climate change may push grizzlies north, increasing future hybridization, scientists agree hybrids aren’t better adapted to changing Arctic. Polar Bears International’s senior research director Geoff York: “Hybridization isn’t viable evolutionary strategy for polar bears. This report confirms climate adaptation won’t come via hybridization.”

Co-author Dr. Ruth Rivkin (University of Manitoba/San Diego Zoo Wildlife Alliance) highlighted the chip: “We’re proud this enables rapid/precise hybrid ID—critical tool amid rising species contact in changing climate.”

Key Tech Advance for Large Carnivore Conservation

The Ursus maritimus V2 SNP chip marks Arctic megafauna conservation milestone. Backed by Environment and Climate Change Canada’s Genomic R&D Initiative, it enables high-resolution genetic analysis, 100% accurately detecting grizzly-polar hybrids. It confirms field individuals’ genetic ID and monitors population diversity.

Lead author Dr. Joshua Miller (MacEwan University): “Our tech assesses 8,000+ markers, key to understanding species resilience amid changing environments.”

Chip development leveraged 1966+ Canadian monitoring data/samples via university/environmental org/conservation collaboration—exemplifying applied science improving at-risk species management amid rapid climate shifts.

This study transforms polar-grizzly hybridization debate. Climate alters habitats/raises contact, but hybridization remains exception, not norm. Far from adaptive pathway, crosses show limited frequency/ecological viability.

With advanced genetics/conclusive data, polar bear conservation refocuses on habitat, diet, warming Arctic survival—not improbable southern hybridization.

Reference:

• Polar Bears International/Hybridization Extremely Rare Between Grizzly and Polar Bears, Study Finds. Link

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