Corridor success in connecting tiger metapopulation

One way to measure the effectiveness of linkages is by examining the level of gene flow between populations connected by corridors. For a corridor to have high functionality, it should show evidence of high genetic mixing between the populations it connects, providing evidence that individuals are able to disperse easily. While gene flow through corridors has been examined in several species before, until recently few have ever looked at in large cats over a large landscape. With their new study in Proceedings of the Royal Society, Sandeep Sharma and colleagues provide evidence of not only current gene flow through corridors between critically small tiger populations in India, but also historical gene flow that can be compared to current rates.

Their results conclusively show that forested corridors are effective in maintaining gene flow between tiger populations in four wildlife preserves connected by corridors. There was significant reduction in gene flow between reserve pairs with degraded corridors compared to those with well maintained corridors. The implication is that without these corridors, this metapopulation would remain as fragmented populations with less chance of individual mixing, leading to higher probabilities of extinction. Further, rates of historic gene flow occurred at significantly higher rates than contemporary gene flow. The increased fragmentation of habitat along with human encroachment on tiger home ranges over the past 300 years has led to population isolation that has been saved in part from low genetic diversity through the presence of corridors. With these findings,there is strong compelling evidence that corridors play an important role in maintaining gene flow, and can contribute greatly to preventing endangered species such as tigers from going extinct.