Mitochondrial DNA variation, phylogeography and social organization of Asian elephant (Elephas maximus) of North East India

North east India is one of the exotic hotspots for Asian elephant (Elephas maximus) and harbors about half of the global population of the Asian elephant. Here we present the first population genetic study of free-ranging Asian elephants, examining within- and among-population differentiation by analyzing mitochondrial DNA (mtDNA) differentiation across the Brahmaputra valley and elephant reserves of North east India. Surprisingly, the population here had shown lower mtDNA haplotype diversity with little mtDNA differentiation among localities within the Brahmaputra valley. This suggests extensive gene flow in the past, which is compatible with the home ranges of several hundred square kilometers for elephants in this region. Conversely, the Brahmaputra valley population is genetically distinct at a mitochondrial level than other tested elephant populations. These results significantly indicate the importance of population bottlenecks, social organization, and bio-geographic barriers in shaping the distribution of genetic variations among Asian elephant populations in North east India.