Preserving The Genetic Diversity Of Sumatran Rhinos

Genetic studies suggest that breeding centers and a cell bank are necessary to preserve the genetic diversity of critically endangered Sumatran rhinos.

AsianScientist (May 17, 2018) – To save the critically endangered Sumatran rhinoceros (Dicerorhinus sumatrensis), scientists are recommending that two subpopulations should be combined into a single breeding center. These findings have been published the Journal of Heredity.

The population of Sumatran rhinoceros, the little-known and smallest member of the rhinoceros family, is dwindling. Today, between 30 and 100 individuals are isolated on the islands of Sumatra and Borneo in Southeast Asia.

In the present study, researchers urged conservationists to translocate the two island groups—representing two subspecies of the Sumatran rhino—and create a cell bank to preserve the genetic diversity uncovered by this work.

“It is heartbreaking as a geneticist to recommend that two subspecies, which are probably as different as humans were from the Neanderthals, should be combined into a single conservation unit,” said principal investigator Professor Alfred Roca at the University of Illinois.

The researchers analyzed 13 samples taken from zoos and the wild, as well as 26 museum specimens, to reveal differences in the species’ mitochondrial DNA, the small proportion of the genome that is passed down only from mothers to their offspring.

The study exposed 17 distinct mitochondrial haplotypes, a group of genes inherited from one parent, that can be used to trace a species’ migrations and distribution across thousands of years. The mitochondrial DNA also confirmed the classification of three subspecies of Sumatran rhinos: D. s. lasiotis (likely extinct), D. s. harrissoni, and D. s. sumatrensis.

In the wild, Sumatran rhinos are solitary creatures, only coming together to breed. In such small numbers, it is increasingly difficult for them to find each other in their mountainous habitat. What’s more, if they are not able to mate, females develop reproductive diseases that prevent them from successfully breeding.

“My strongest recommendation is that they are brought into breeding centers as soon as possible because they aren’t going to survive in the wild in such low numbers,” Roca said. “A population of ten individuals loses five percent of their genetic diversity each generation, which they cannot spare.”

This genetic erosion can be prevented or slowed by combining the remaining rhinos to create a larger population. A century of captive breeding efforts has yielded few babies, but recent successes suggest that ex situ breeding facilities could help save this species from the brink of extinction—the result of poaching and habitat loss due to legal and illegal logging for desirable hardwoods.

To ensure the long-term genetic health of the species, the authors implore conservationists to preserve the genomes of every living Sumatran rhino. In the future, preserved cell lines could be used to create artificial gametes, to reverse the effects of inbreeding and harmful mutations.

“We may one day be able to use stored cells to bring back what was once lost, reversing the effects of inbreeding, drift and our own folly,” Roca said. “Because they are at such low numbers, every single living Sumatran rhino is genetically very valuable, and preserving cells with genetic material from each surviving individual is of paramount importance.”

The article can be found at Brandt et al. (2018) Genetic Structure and Diversity Among Historic and Modern Populations of the Sumatran Rhinoceros (Dicerorhinus sumatrensis).


Source: University of Illinois.
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