uld result in a younger estimated timing of decline, while a lower generation time would result in an older estimated timing of decline.
The differences between the observed patterns of population differentiation between mitochondrial and nuclear markers could be because of the lower effective size for mitochondrial DNA , or due to interactions between mode of inheritance and sex-biased dispersal. Female tigers have smaller home ranges than males, with daughters inheriting the home range of their mothers . This would result in strong population subdivision for maternally inherited mitochondrial DNA. On the other hand, biparentally inherited nuclear (microsatellite) data are consistent with expectations for a large carnivore species that exhibits long-range dispersal movements . Discordant patterns for population differentiation between mitochondrial and nuclear DNA are common for mammals with female philopatry and male-biased dispersal . It is interesting that population subdivision between Southern and Central India is not significant for both mitochondrial and nuclear DNA, suggesting dispersal through a wide range of habitat types as well as relatively recent fragmentation of the formerly contiguous tiger habitats in peninsular India.
Implications for conservation
Our results are important for global tiger conservation because they suggest that Indian tiger populations are critical for species recovery. However, because tiger habitats in India are often small, disjunct and fragmented, conservation options are limited. Ecological studies ,, have identified a few protected landscapes in India with high tiger densities and potential connectivity. Conservation efforts must prioritize these tiger populations in larger landscapes like the Western Ghats, Central India and the alluvial flood plains in the Himalayan foot hills that support high potential tiger densities, and relatively larger populations.
Genetic diversity retains the history of a species ,, and is vital for survival and future adaptation to changes . Although it is possible that other tiger populations outside of India harboured increased genetic variation in the past, our results show that currently Indian tiger retain the majority of the species' genetic variation. This suggests subspecies-based conservation criteria are inappropriate. Despite having experienced recent demographic declines, extensive habitat loss, extant Indian wild tigers retain 76% of the mitochondrial diversity and 63% of the species' nuclear genetic diversity and are adapted to a greater diversity of habitats ,. They are thus critically important from demographic, evolutionary and ecological perspectives for future survival and recovery of the species. More than a billion people, afflicted by poverty and yet experiencing rapid economic growth live in India. That Indian tigers have managed to retain their genetic diversity in the face of such high anthropogenic pressure provides some hope for species survival in the future.
Materials and Methods
Sampling and DNA extraction
Samples were opportunistically collected from wild individuals living inside protected areas and national parks spanning all over India. We collected 71 fecal samples and two tissue samples from most of the tiger habitat in India. Tissue samples were collected from poached animals with permissions. All samples were collected in sterile vials and preserved in absolute alcohol until processed. To avoid the effects of inbreeding in our analyses, samples were collected spatially far apart within a protected area (at least 15 km apart). DNA extraction and species identification was performed by methods explained in Mukherjee et al. . Sampling information is provided in supplementary material (Table S1). We generated mitochondrial DNA data for 54 samples and STR data for 58 samples. In addition to the samples collected in this study, we used genetic data from all tiger subspecies (Indo-Chinese, Malayan, Sumatran and Siberian, in addition to Indian tigers) from Luo et al. . All genetic data for tigers outside the Indian subcon