We studied the DNA of African and Asian leopards and found big differences
Leopards are among the most widespread carnivores today, living in a wide range of habitats, from deserts to rainforests, and from the lowland plains to the mountainous highlands.
Over the past century, they’ve experienced extreme habitat losses due to human activity, both directly from hunting and indirectly from habitat reduction and prey competition. This has led to the land they occupy being reduced by over 50% in Africa, and over 80% in Asia, involving the local extinction of many populations.
Genetic analysis of leopards is important to understand their population history, structure and dynamics. Particularly important is the analysis of whole nuclear genomes, which means all the DNA contained in the cell core – approximately 2.5 billion DNA bases (pairs of DNA building blocks).
In new research, we studied the genomes of modern and historical leopards, using samples gathered from an unusual place – natural history museums. And we found a surprising level of genetic separation between leopards from different parts of the world.
Normally, genetic analysis involves collecting fresh tissue samples. For leopards, doing this would be extremely difficult. The animals are hard to track down, particularly in areas where they are rare, and invasive sampling can be bad for the animal.
Animals bred in zoos may not be a good option as they may be mixtures of multiple wild populations. Getting samples from areas where they have been eradicated is not possible at all. For these reasons, we turned our sampling efforts to museums.
Natural history museums across the world are filled with skins, skeletons and even complete taxidermy specimens, often collected decades and decades ago. It’s a lot more challenging to extract genetic material from these old specimens, both from a technical and a financial point of view, because the DNA in such samples is more degraded, and sometimes includes large amounts of contaminant DNA in addition to the leopard DNA. But doing so allowed us to collect data from leopards covering their entire distribution, both current and historical.
This would have been near impossible if we only looked for fresh tissue samples. The collection of this genetic data allowed us to investigate the global population dynamics of leopards, with unprecedented resolution.
We collected material from many museum specimens, and investigated the DNA quality in each. Then, we selected the best samples from which to sequence hundreds of billions of bases of DNA. Using high powered computational resources we compared the DNA from all leopards to each other, and ran a range of different types of analyses to better understand how they differ.
African and Asian leopards
One of the most striking revelations we found was a marked distinction between African and…