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English Bulldogs' Low Diversity

English bulldogs have such low genetic diversity that researchers are unsure whether their health can be improved without crossing them with another breed, LiveScience reports.

English Bulldogs, known for their squishy faces and wrinkly coats, are prone to breathing, skin, and other issues. The breed all descends from a founder population of 68 individuals and underwent selective breeding for certain traits.

Researchers from the University of California, Davis, studied the genetic diversity of 102 registered English bulldogs from the US and Europe, including ones that presented with health problems. They examined the dogs' maternal and paternal haplotypes, various STR loci, allele frequencies, and runs of homozygosity. As Niels Pedersen and his colleagues report in Canine Genetics and Epidemiology, their sample harbored four paternal haplotypes, one of which was found in 93 percent of dogs, and they had an average of 6.45 alleles per locus. In particular, they noted a loss of diversity in immune-related gene regions.

"Improving health through genetic manipulations presumes that enough diversity still exists to improve the breed from within, and if not, to add diversity by outcrossing to other breeds," Pedersen says in a statement. "We found that little genetic 'wiggle room' still exists in the breed to make additional genetic changes."

Crossing English bulldogs with other breeds might alleviate some of their health issues, but LiveScience notes that breeders might not then consider the dogs to be English bulldogs any more.