A new study by Clemson University into the impact of landscape on tiger and leopard gene flow reveals two interesting human impacts on tiger genes caused by man. The first splitting of tiger genes into two distinct clusters happened 700 years ago with the arrival of agriculture. The second splitting of genes into four clusters happened with the arrival of the British.
The study was looking at the impact of landscape use on the gene flow of tigers and leopards. The researchers examined the genetic profile of the estimated 273 tigers and 217 leopards living in four distinct populations in the 17,375-mile Satpura-Maikal region of central India, then used computer modeling to compare contemporary and historical gene flow among the region’s tiger and leopard populations.
The study by Sandeep Sharma and Trishna Dutta, with colleagues from the Smithsonian Conservation Biology Institute, showed that tigers had two major splits in their gene-flow during recent times.
The first occurred 700 years ago when great swathes of Indian forest was turned over to agriculture during the early Mughal era. The second split occurred about 200 years ago when the British arrived and cleared large areas of forest for timber to build railways and ships – not to mention the boost in tiger hunting.
The study published in the journals Proceedings of the Royal Society B: Biological Sciences and Evolutionary Applications also has important implications for modern day conservation. The study looked at tigers and leopards in 4 protected areas. Some parts of the protected areas are still connected with forested landscape while other parts are connected with degraded corridors.
The study found that those areas which maintain high quality forested areas still had good gene-flow between the tiger and leopard populations indicating a healthy and sustainable population. The areas connected with degraded and fragmented forest corridors saw the biggest declines in gene-flow between animals.
“The viability of the forest corridors connecting tiger habitats has a direct affect on a tigers’ chance of finding an unrelated mate and on the ability of tiger populations to maintain genetic diversity,” Dutta said. “As we know, genetic diversity allows species to survive disease and habitat stress and encourages long-term survival.”
While the areas of study were protected from development the connecting wildlife corridors are often without any legal protection. In two of the study areas the Indian Ministry of Environment and Forests has just given permission for coal mining in the connecting corridors despite the disturbance that the developments will bring.
“Mining brings with it many ancillary habitat disruptions,” Sharma said. “There are settlements, roads and infrastructure that will have an inevitable impact on the corridors and possibly obstruct the flow of genes between the habitats.”
In cases where habitats become islands and a genetic bottleneck occurs, dramatic human intervention is required to save isolated populations of cats from the perils of inbreeding.
“Moving animals is inefficient, costly and stressful for the animals. There is also no guarantee that the animals will mate,” Sharma said. “And building manmade corridors is very expensive and logistically challenging. Since we now know that the existing corridors play such a vital role in long-term survival, the best way to enable their success is to take a landscape-scale approach to conservation and protect the corridors from further damage.”