A study from UCLA has revealed that animals with more genetic variation are the best candidates for relocation. The researchers analyzed the outcomes for more than 9,000 tortoises that were moved from the Mojave Desert to Nevada’s Ivanpah Valley. The study revealed that genetic variation was the strongest predictor of survival.
From 1997 to 2014, the U.S. Fish and Wildlife Service moved tortoises that had been displaced by development to a large translocation site that spanned about 39 square miles. The researchers expected that animals would fare best if they were adapted to living in areas that were closest to the site.
However, the study showed that the tortoises’ place of origin did not have an influence on their chances of survival. Instead, tortoises with lots of genetic variation were much more likely to survive after their relocation, explained study senior author Professor Brad Shaffer.
Most living organisms have two copies of their entire genome, with one copy from each parent. Animals that have greater differences among these copies have higher levels of heterozygosity. The researchers found that the surviving tortoises had a 23-percent higher level of heterozygosity.
“It flies in the face of what we know from other translocation studies, but lots of genetic variation was hands-down the best predictor of whether a tortoise lived or died,” said Professor Shaffer. “Relocating endangered plants and animals is increasingly necessary to counteract the effects of climate change, and this gives us a new tool to increase survival rates.”
Study lead author Peter Scott said that although the relationship between heterozygosity and survival was well supported by the study, it’s unclear why greater genetic variation is linked to survival rates.
“Potentially, individuals with higher heterozygosity have more genomic flexibility,” said Scott. “It’s likely that tortoises with more variation have a better chance of having one copy of a gene that works really well in stressful or new environments compared to those individuals with two identical copies that only work really well in their environment of origin.”
“The only reason we could do this study was because the U.S. Fish and Wildlife Service was incredibly forward-thinking when they set up the translocation site and tracked who lived and died,” explained Professor Shaffer. “Many died, and no one was happy about that. But we can learn a lot from that unfortunate result to help conservation management improve.”
“When thinking about moving animals or plants out of danger, or repopulating an area emptied by wildfire, now we can easily and economically measure genetic variability to better gauge the survival probability of those translocated individuals. It’s not the only criteria, but it’s an important piece of the puzzle.”
The study is published in the journal Science.