African, Asian Lion Populations Genetically Diverse, Research Suggests
GenomeWeb News - NY,USA By a GenomeWeb staff reporter
NEW YORK (GenomeWeb News) – Lion populations contain unexpected genetic diversity, according to a new study.
An international team of researchers used a combination of mitochondrial DNA, Y-chromosome, biparental nuclear DNA, and feline immunodeficiency virus sequence data to characterize lion population genetics and evolutionary history. Their work, appearing online today in PLoS Genetics, suggests that existing lion populations fall into at least eleven genetic groups, challenging the notion that African lions fall into one large genetic group. That, in turn, provides insights into potential lion conservation strategies.
"We refute the hypothesis that African lions consist of a single panmictic population," senior author Warren Johnson, a staff scientist with the National Cancer Institute's Laboratory of Genetic Diversity, and his colleagues wrote, "highlighting the importance of preserving populations in decline rather than prioritizing larger-scale conservation efforts."
In the past, lion fossils dating back millions of years have been unearthed in eastern and southern Africa. The animals appear to have spread from Africa to other parts of the continent and into Eurasia and the Americas. These days, though, remaining free-ranging lion populations are found in just a few primary regions, such as sub-Saharan Africa and India's Gir Forest, where researchers estimate that there are fewer than 50,000 lions remaining.
The team compiled genetic data from 357 lions from Africa and Asia, focusing on sequences from mitochondrial genes, the SRY-3' UTR on the Y-chromosome, two biparental nuclear genes, and 22 microsatellite markers.
They also compared sequences from FIV samples, since the viruses vary genetically from one lion population to the next. FIV genetics, meanwhile, added another layer to the picture. The virus is endemic to eight of the 11 lion populations, absent only in populations in India, Namibia, and the Botswana/Kalahari region.
Overall, the team found eleven genetically distinct groups of lions: one each in Namibia, South Africa's Kruger National Park, Tanzania's Ngorongoro Crater, Kenya, Uganda, and Gir, India, two groups in Botswana, and three in the Serengeti National Park.
In Botswana, the researchers found one distinct genetic cluster of lions in northern Botswana and another in southern Botswana and the Kalahari in South Africa. In the Serengeti region, on the other hand, three genetic clusters were found in an overlapping region.
Along with their assessment of existing lion populations, the researchers were also able to make inferences about past migration events. Their analysis of lion and FIV genetic data indicates that East African lions are genetically older than other lions, supporting the notion that lions were present in East Africa before spreading to other regions sampled.
The genetic patterns in each region also revealed information about some past lion migration events. For instance, the team concluded that lion populations living today originated in East and Southern Africa during the Pleistocene period, between 169,000 and 324,000 years ago.
From there, the researchers inferred that there were two major migration events. The first migration, from southern and eastern Africa to Central and North Africa and Asia, appears to have occurred during the Late Pleistocene about 100,000 years ago. More recently, during the Pleistocene/Holocene transition (some 7,000 to 14,000 years ago), lions appear to have migrated from Southern Africa towards East Africa, inter-breeding with other lion populations on the way.
"[W]e found substantial population subdivision, reduced gene flow, and large differences in FIVPle sequence and sero-prevalence among lion populations, as well as evidence of historic secondary contact between populations," the authors wrote.
Beyond providing information about past lion populations, the team noted, the findings could have implications for those designing lion conservation schemes. Because there appears to be a substantial amount of genetic diversity between different lion populations, genetic clusters could be lost should individual lion populations disappear.
"[E]mploying a bottom-up perspective that prioritizes populations, rather than large-scale units (e.g. all African lions), might preserve and maintain lion diversity and evolutionary processes most efficiently," the authors wrote.