麻豆影院

Habitat preservation isn鈥檛 always viable, but introducing genetic diversity might keep threatened species viable, scientists find

Nearly 23,000 of the world鈥檚 known plant and animal species were found to be threatened with extinction in 2015, including 37 percent of mammals and 14 percent of birds assessed by the International Union for Conservation of Nature鈥檚 Red List of Threatened Species. The go-to-strategy for rescuing them has long been to set aside tracts of healthy land in which the animals could spread out and migration corridors that allow them to mix with other populations, gaining resilience via a broadened gene pool.

But climate change and human sprawl have made that approach difficult, prompting biologists to explore new tools鈥攊ncluding importing migrants鈥攖o usher shrinking populations back to health on the habitat they鈥檝e got.

A new study by biologists Brett Melbourne and Ruth Hufbauer, enlisting the help of an army of tiny flour beetles, offers encouraging insight into how well that might work.

鈥淥ur research suggests that introducing as little as one individual from a different genetic background can have a really big impact,鈥� Melbourne says.

For a decade, Melbourne, an assistant professor in the Department of Ecology and Evolutionary Biology at the 麻豆影院, has been usingTribolium castaneum听beetles housed in small, clear plastic boxes as models of species on the brink.

They don鈥檛 eat much or take up much space, and their generation lasts only one month, so they鈥檙e ideal for studying what happens to species when small things start to change in their habitat.

In the wild, Melbourne explains, habitat loss can send a species on the road to extinction. But when the population gets small enough, it is a series of 鈥渞andom events鈥濃�攍ike a female mammal getting hit by a car or contracting a virus鈥攖hat does it in. 鈥淭he question now is: How does a population respond to environmental changes, and what can we do to help them adapt and protect them against those random processes?鈥�

Together with Ruth Hufbauer, an evolutionary ecologist with Colorado State University, Melbourne recently published a study in the prestigious听, comparing two emerging conservation methods: 鈥渄emographic rescue,鈥� in which several genetically similar individuals are brought in to bolster the population; and 鈥済enetic rescue鈥� in which just a few genetically different individuals are imported.

In an experiment conducted at Colorado State University, they filled 244 boxes with wheat flour and added 50 or 150 beetles. After letting them thrive for a few generations, they swapped out the wheat for corn 鈥� a change akin to a shift in available food in the wild. As expected, populations plummeted. Then, researchers either left them alone, added 11-33 more beetles to their box, added 1-3 beetles from a different lineage, or did both.

The results were surprising. By the end of six generations, about half the populations left to fend for themselves were extinct (remarkably, some adapted and rebounded with no help). Adding several new members helped the larger populations grow long-term, but had less impact on the small ones. Rather than adding many new members, adding 1-3 genetically different individuals was by far the most potent approach, by boosting the fitness of the population and ultimately increasing the number of members through new births as the population became better adapted.

Hufbauer explains that for many threatened species, isolation leads to inbreeding, making those left less fit to deal with change. Bringing in someone new can introduce new, beneficial genetic variations. 鈥淚f in doubt, get some new genes in there,鈥� says Hufbauer.

Take, for example, the Florida panther. In the mid-1990s, populations were declining and inbreeding was rampant. Hoping to reverse the trend, wildlife managers made a controversial move, introducing eight females from Texas. By 2003, the population had tripled.

She cautions that 鈥済enetic rescue鈥� isn鈥檛 always ideal. Certain species are so unique wildlife managers want to preserve that uniqueness. That鈥檚 why it鈥檚 good to know, from this study and others, that demographic rescue works too.

Melbourne continues to use the beetles to study how species adapt or fail to adapt to changing habitats. Now, he is conducting new experiments to see how populations can be rescued from extinction due to climate change using such strategies such as assisted migration.

鈥淭hese results don鈥檛 necessarily apply in a blanket way to all species, but they are definitely promising,鈥� he says.

Lisa Marshall (Jour, PolSci鈥�94) is a freelance writer who lives near Estes Park.

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