A new study reveals that hidden genetic variation allowed a small group of brown tree snakes to overcome inbreeding and become a major invasive force on Guam. Researchers identified more than 19,000 structural variants in the snakes' DNA, many linked to immunity and smell. The findings were published on July 24 in Science Advances.
The brown tree snake reached Guam after World War II, likely aboard military cargo planes. Its population grew rapidly despite starting from just a few individuals, driving many native forest birds to extinction and causing frequent power outages.
University at Buffalo researchers used long-read DNA sequencing to examine the genome. They found structural variants concentrated in genes tied to immune function and olfaction, which may have supported adaptation and survival in the new environment.
"The brown tree snake is maybe not wildly diverse, but it has important sources of genetic diversity that have been underappreciated," said corresponding author Trevor Krabbenhoft. The team obtained samples through collaboration with the U.S. Geological Survey.
The results suggest that endangered species with small populations may also retain more genetic flexibility than previously thought. Scientists do not yet know whether the variants originated before or after the snakes arrived on Guam.