KOTA KINABALU: Inbreeding is causing health and genetic problems among Asian elephants, with Bornean elephants showing the highest levels, according to scientists.
Director of the Danau Girang Field Centre and Cardiff University professor Dr Benoit Goossens said the finding came from a study analysing the complete genomes of 81 Asian elephants from all four recognised subspecies.
Published in the scientific journal Genome Biology and Evolution, the study found that about 65% of the DNA in Bornean elephants was inherited identically from both parents – a clear sign of long-term inbreeding.
Sumatran elephants also showed elevated levels of inbreeding, at about 35%, while elephants on the Asian mainland and in Sri Lanka recorded considerably lower levels, at around 11% and 10% respectively.
Goossens, a co-author of the study, said introducing elephants from other populations could potentially reduce inbreeding by bringing new genetic variation into isolated populations.
However, he stressed that such measures must be carefully considered to avoid compromising local genetic adaptations.
“For example, you want to avoid losing local genetic adaptations to the environment. Further research is therefore needed before such measures can be applied responsibly,” Goossens said in a statement yesterday.
The approach, known as genetic rescue, is being considered as a potential conservation measure for Bornean elephants.
“Ecological, practical and ethical considerations all play an important role,” said Goossens.
The study found substantial differences in the genetic health of the four Asian elephant subspecies, all of which face varying levels of pressure.
The Asian elephant (Elephas maximus) is classified as endangered by the International Union for Conservation of Nature.
Habitat loss and fragmentation, human-elephant conflict and poaching have reduced and isolated populations, increasing the risk of inbreeding.
The researchers obtained many of the blood samples from elephants now living in European and North American zoos.
The EAZA Biobank, an international repository for zoo animal blood samples, together with detailed records of the animals’ origins, allowed researchers to accurately assign the DNA profiles to the respective subspecies.
First author Jeroen Kappelhof, a PhD candidate at Wageningen University and Research, and affiliated with Rotterdam Zoo, said inbreeding poses a twofold risk.
“On the one hand, genetic diversity declines. This makes it more difficult for populations to adapt to changes such as new diseases or climate change,” he said.
“Inbreeding also increases the likelihood of harmful inherited traits being expressed, potentially resulting in reduced fertility.
“Both processes make populations more vulnerable and increase their risk of extinction.”
Researchers identified inbreeding by examining long stretches of DNA inherited identically from both parents, a pattern that occurs more frequently when related animals reproduce in small, isolated populations.
Kappelhof said one surprising finding was that despite differences in inbreeding, the four subspecies still shared a large proportion of their original genetic diversity.
This suggests they have not been separated from each other for very long in evolutionary terms, while the differences seen today are largely due to some populations losing more genetic variation than others.
The findings suggest genetic rescue could offer conservation prospects for populations with low genetic diversity.
The study was funded by the Dutch Research Council and led by researchers from Wageningen University and Research, and Vrije Universiteit Amsterdam, in collaboration with international partners.
