Tigers of Central India

[Pckts]

Spatial genetic analysis reveals high connectivity of tiger (Panthera tigris) populations in the Satpura–Maikal landscape of Central India

Abstract
We investigated the spatial genetic structure of the tiger meta-population in the Satpura–Maikal landscape of central India using population- and individual-based genetic clustering methods on multilocus genotypic data from 273 individuals. The Satpura–Maikal landscape is classified as a global-priority Tiger Conservation Landscape (TCL) due to its potential for providing sufficient habitat that will allow the long-term persistence of tigers. We found that the tiger meta-population in the Satpura–Maikal landscape has high genetic variation and very low genetic subdivision. Individual-based Bayesian clustering algorithms reveal two highly admixed genetic populations. We attribute this to forest connectivity and high gene flow in this landscape. However, deforestation, road widening, and mining may sever this connectivity, impede gene exchange, and further exacerbate the genetic division of tigers in central India.
Keywords: Central India, connectivity, non-invasive genetic analysis, Panthera tigris, spatial genetics, tiger
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Introduction
The tiger (Panthera tigris) is the largest extant cat species and has become an iconic conservation emblem for Asian forest ecosystems (Seidensticker 2010). Tigers historically ranged widely across Asia (Mazák 1981). By 2006, their occupancy had been reduced to 7% of their historical range, which was fragmented into 76 Tiger Conservation Landscapes (TCL) that were hypothesized to each contain one meta-population (Dinerstein et al. 2007). The Indian subcontinent has the largest number of TCLs (40, of which 11 are of global priority). These TCLs are home to 60% of wild tigers of the world (Sanderson et al. 2006) and the majority of this population is found in the alluvial flood plains of the Himalayan foothills, the Central Indian highlands, and the forests of Western Ghats (Jhala et al. 2011).
The “Central Indian highlands” is an important biogeographic province (Rodgers et al. 2002) and one of the six landscape complexes defined for tiger conservation in India (Jhala et al. 2011). It is occupied by 35% of India's tiger population, in 47% of India's remaining tiger habitat (Jhala et al. 2011). The Satpura–Maikal landscape is located in the central Indian highlands and categorized as a global-priority TCL for its potential to support long-term persistence of tigers (Dinerstein et al. 2007). It supports an estimated 12% of India's tiger population and contains 13% of India's tiger habitat (Jhala et al. 2011).
Tiger populations in India have been increasingly isolated over the last century due to habitat fragmentation and population decimation (Project Tiger-Tiger Task Force report 2005; Jhala et al. 2011). The genetic deterioration of insular populations can be prevented by gene exchange with neighboring populations by means of dispersing individuals and their successful breeding in the new population, thus maintaining a large and diverse gene pool (Bohonak 1999). Large terrestrial predators often exhibit limited genetic subdivision because they have high rates of dispersal-mediated gene flow (Wayne and Koepfli 1996).
In previous studies on the population genetics of tigers, various molecular methods revealed very low to moderate levels of genetic diversity in the tiger population of the Indian subcontinent. Shankaranarayanan et al. (1997) found that average heterozygosity was 0.28 in the RAPD (random amplified polymorphic DNA) analysis and 0.23 at three microsatellite loci in a study on the captive tigers in Indian zoos. Wentzel et al. (1999) also found very low levels of genetic variation in tigers at mitochondrial and nuclear genome segments. Luo et al. (2004) used 30 polymorphic microsatellite markers on Indian tigers and reported average observed heterozygosity of 0.524 (±0.039 SD), and average allele per locus of 3.5 (±1.22 SD). Mondol et al. (2009a) reported that Indian tigers are the most diverse among all tiger sub-species and have more than half of the extant genetic diversity in the species.
Recently, the tiger populations in India were classified into six landscape complexes on the premise that the habitat in each complex was contiguous in the recent past and the tigers living in them probably share a common gene pool (Jhala et al. 2011). However, this landscape taxonomy of tiger population sub-structuring was not based on an actual analysis of the genetic structure and gene flow of tiger meta-populations. Therefore, in this study, we aimed to investigate the patterns of genetic structure of a spatially extensive meta-population of tigers in central India (one of the six landscape complexes proposed by Jhala et al. 2011) to test the premise of this taxonomy.
In this paper, we present the results of our study of genetic diversity and fine-scale spatial genetic structure of tiger populations in the Satpura–Maikal landscape of central India using multilocus genotypic information from non-invasively collected samples. This landscape has lost more than 75% of its forest cover to farmlands and urbanization in the last 300 years (S. Sharma, T. Dutta, J. E. Maldonado, T. C. Wood, H. S. Panwar, J. Seidensticker, unpubl. data). This anthropogenic transformation of land may have posed a barrier to dispersal and gene flow among tiger populations and led to genetic subdivision. Therefore, we tested for genetic structure that might have been created by potential impediments to tiger dispersal and risks posed by the features in the existing corridors.
Our tests for genetic subdivision in this tiger meta-population were based on (1) assessing the genetic variation and estimating the population-level genetic difference by calculating and comparing FST and genetic distances between tiger populations, (2) by testing the pattern of isolation by distance (IBD) in this meta-population, and (3) using two different Bayesian clustering methods that utilize individual-based information to decipher underlying genetic subdivision patterns. In the last century, the tiger population in India has experienced a dramatic demographic decline that may have eroded the genetic variation and left a genetic signature of a bottleneck in this population. We used two different approaches to test for evidence of a genetic bottleneck in this meta-population.
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Materials and Methods
Study area and sampling
Our study area in the Satpura–Maikal landscape in central India covers approximately 45,000 km2 (21.15–22.8°N and 76.5–81.05°E). The Satpura range is one of the oldest mountain ranges in the world and, together with the Vindhyachal range in the north and the Maikal range in the east, forms the catchments of the Narmada and the Tapti rivers and their tributaries (Krishnan 1982). Our study area consisted of the five major tiger reserves of this landscape: Kanha Tiger Reserve (Kanha), Bori-Satpura Tiger Reserve (Satpura), Pench MP (Madhya Pradesh) and Pench Mh (Maharashtra) Tiger Reserves (combined we refer to these two as Pench; as they are geographically connected to each other, but located in different states), and Melghat Tiger Reserve (Melghat), along with the forest corridors connecting these reserves. Kanha is connected to Pench and located toward the east of the landscape, while Melghat has a corridor with Satpura and lies to the west of the landscape (Fig. 1a). Tigers and their prey species were reported from these two corridors (Jhala et al. 2011). However, the intervening landscape matrix is composed of agricultural land and fragmented forest patches, interspersed with numerous small villages and towns (Jhala et al. 2011). Details describing the climatic and vegetation attributes of these tiger reserves are in Table S1.
Abstract
We investigated the spatial genetic structure of the tiger meta-population in the Satpura–Maikal landscape of central India using population- and individual-based genetic clustering methods on multilocus genotypic data from 273 individuals. The Satpura–Maikal landscape is classified as a global-priority Tiger Conservation Landscape (TCL) due to its potential for providing sufficient habitat that will allow the long-term persistence of tigers. We found that the tiger meta-population in the Satpura–Maikal landscape has high genetic variation and very low genetic subdivision. Individual-based Bayesian clustering algorithms reveal two highly admixed genetic populations. We attribute this to forest connectivity and high gene flow in this landscape. However, deforestation, road widening, and mining may sever this connectivity, impede gene exchange, and further exacerbate the genetic division of tigers in central India.
Keywords: Central India, connectivity, non-invasive genetic analysis, Panthera tigris, spatial genetics, tiger
Figure 1

(a) Map of the Satpura–Maikal landscape with its location in India (inset). Red dots represent locations of individual tigers identified in each tiger reserve (Orange boundary) and corridors using multilocus genotype data. Pie charts show admixed ...

During April–June 2009 and November 2009–May 2010, we conducted extensive surveys covering 15,000 km of forest trails and roads in these five tiger reserves and the corridors among them to collect fecal samples. We used systematic sampling inside the tiger reserves using a 10-km2 grid as the sampling unit (Fig. S1). All grids inside tiger reserves were sampled at least once except those that were completely occupied by dense human populations, barren-land, inaccessible terrain, or water bodies. We used stratified random sampling in corridors. Each corridor was stratified based on previous information about tiger occupancy (Jhala et al. 2008); grids with known occupancy were searched preferentially. We identified tiger fecal samples by their size and associated signs such as scrapes and pugmarks. We collected the outermost layer of the scat weighing approximately 5–10 g. Hair and claw samples were also collected opportunistically from trees marked by tigers and from kill sites. Only hairs that were found in a single clump were collected to avoid cross-individual contamination (see also error-checking methods below). Sample locations were recorded with a GPS unit (Garmin International, Inc., Olathe, Kansas) along with habitat information. Samples were preserved in 100% ethanol and stored at room temperature until further analysis.


the remainder of the study is here... http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3568842/ Reply