Abstract
Despite massive global conservation strategies, tiger populations continued to decline until recently, mainly due to habitat loss, human-animal conflicts, and poaching. These factors are known to affect the genetic characteristics of tiger populations and decrease local effective population sizes. The Terai Arc Landscape (TAL) at the foothills of the Himalaya is one of the 42 source sites of tigers around the globe. Therefore, information on how landscape features and anthropogenic factors affect the fine-scale spatial genetic structure and variation of tigers in TAL is needed to develop proper management strategies for achieving long-term conservation goals. We document, for the first time, the genetic characteristics of this tiger population by genotyping 71 tiger samples using 13 microsatellite markers from the western region of TAL (WTAL) of 1800 km2. Specifically, we aimed to estimate the genetic variability, population structure, and gene flow. The microsatellite markers indicated that the levels of allelic diversity (MNA = 6.6) and genetic variation (Ho = 0.50, HE = 0.64) were slightly lower than those reported previously in other Bengal tiger populations. We observed moderate gene flow and significant genetic differentiation (FST= 0.060) and identified the presence of cryptic genetic structure using Bayesian and non-Bayesian approaches. There was low and significantly asymmetric migration between the two main subpopulations of the Rajaji Tiger Reserve and the Corbett Tiger Reserve in WTAL. Sibship relationships indicated that the functionality of the corridor between these subpopulations may be retained if the quality of the habitat does not deteriorate. However, we found that gene flow is not adequate in view of changing land use matrices. We discuss the need to maintain connectivity by implementing the measures that have been suggested previously to minimize the level of human disturbance, including relocation of villages and industries, prevention of encroachment, and banning sand and boulder mining in the corridors.
Highlights
Knowledge of the genetic structure and gene flow in wild animal populations is crucial for making decisions to improve their sustainability
Given the previous ecological knowledge and the lack of genetic information, the present study focused on the following objectives: (1) genetic characterization and determination of population structure; (2) determination of the effect of anthropogenic pressure and recent developmental activity on genetic structure; (3) tracing the demographic history of the Bengal tiger in western region of TAL (WTAL)
Within the scat samples, genotyping error rate varied among loci, allele dropout (ADO) rate ranged from 0% to 17% and false allele (FA) between 0 to 5% (S1 Table)
Summary
Knowledge of the genetic structure and gene flow in wild animal populations is crucial for making decisions to improve their sustainability. Fragmentation and loss of habitat result in the isolation of populations, which in the long-term reduces genetic variation and increases extinction probability due to inbreeding and reduced fitness [19, 20]. The loss of genetic variability in many highly vagile and long-ranging species, such as Ethiopian wolves (Canis simensis) [21], pumas (Puma concolor) [22], Eurasian lynx (Lynx lynx) [23], brown bears (Ursus arctos) [24], jaguars (Panthera onca) [25], and Isle Royale wolves (Canis lupus) [26] has been affected by reduced movements of individuals together with other ecological/biological factors that have inhibited migrating individuals from contributing to gene pools. Knowledge of the patterns of gene flow is crucial for developing conservation plans by identifying population units and source populations that require management [19]
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