Arya News - Habitat loss and fragmentation, human–elephant conflict, and poaching are causing populations to become smaller and increasingly isolated, increasing the risk of inbreeding.
KOTA KINABALU – Inbreeding among elephants has been found to cause health and genetic issues within the species, but further research is needed to find out the most feasible way to address this problem, scientists say.
Danau Girang Field Centre director Dr Benoit Goossens, who is also a professor at Cardiff University, said this was found in a recent study analysing the complete genomes of 81 Asian elephants from all four recognised subspecies.
According to the scientific journal Genome Biology and Evolution, inbreeding, which can lead to a loss of genetic variation and reduce the resilience of populations, has been found in the DNA of Asian elephants.
The Bornean elephants have by far the highest level of inbreeding. In this subspecies, around 65% of the DNA has been inherited identically from both parents, a clear sign of long-term inbreeding, the study found.
Dr Goossens said that though introducing other species into existing herds is seen as one way to reduce the risk of inbreeding, careful consideration has to be taken before implementing them.
“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,” he said in a statement Sunday (Aug 16).
He said if possible, the introduction of animals from other populations could bring new genetic variation into the population and can make populations more resilient.
This approach is known as genetic rescue, Dr Goossens, who is co-author of the study, explained, saying that for the Bornean elephant, the researchers consider this a potential management measure.
Ecological, practical, and ethical considerations all play an important role, he said.
Based on this research, the DNA of Asian elephants tells a concerning story and although all four subspecies are under pressure, there are considerable differences in their genetic health.
The Asian elephant (Elephas maximus) is found across South and Southeast Asia and is classified as Endangered by the the International Union for Conservation of Nature (IUCN).
Habitat loss and fragmentation, human–elephant conflict, and poaching are causing populations to become smaller and increasingly isolated, increasing the risk of inbreeding.
For the study, the researchers obtained many of the blood samples that came from elephants that now live in European and North American zoos.
Thanks to the EAZA Biobank – a kind of international blood bank for zoo animals – and well-documented information on the animals’ origins, the researchers were able to reliably assign the DNA profiles to the correct subspecies.
The analyses show that the genetic health of the four subspecies differs substantially.
Other than the Borneo elephants, the Sumatran elephant also shows elevated levels of inbreeding, at around 35%.
By contrast, populations on the Asian mainland and in Sri Lanka show considerably fewer signs of recent inbreeding, at around 11% and 10%, respectively.
“The risk of inbreeding is twofold,” says Jeroen Kappelhof, first author and PhD candidate at Wageningen University and Research, who is also affiliated with Rotterdam Zoo.
“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.
He said inbreeding increases the likelihood that harmful inherited traits will be expressed, which can, for example, lead to reduced fertility.
Both processes make populations more vulnerable and ultimately increase their extinction risk.
“This is why it is important to identify inbreeding at an early stage,” Kappelhof said, adding that researchers assessed this by looking at long stretches of DNA that were inherited identically from both parents.
He said such patterns arise when related animals reproduce with each other and this happens more often in small, isolated populations, causing inbreeding to increase over generations.
“One surprising finding is that, despite the major differences in inbreeding, the four subspecies still share a large proportion of their original genetic diversity,” says Kappelhof, suggesting that in evolutionary terms, they have not been separated from each other for very long.
He said the differences seen today have mainly arisen because some populations have lost more genetic variation than others, a situation which offers prospects for conservation, as genetic rescue may be an option for populations with low genetic diversity.
The study is part of a Dutch Research Council (NWO-funded research project led by Mirte Bosse (Wageningen University and Research and Vrije Universiteit Amsterdam) and was carried out in collaboration with international research partners.