Abstract
The Sundarbans tiger inhabits a unique mangrove habitat and are morphologically distinct from the recognized tiger subspecies in terms of skull morphometrics and body size. Thus, there is an urgent need to assess their ecological and genetic distinctiveness and determine if Sundarbans tigers should be defined and managed as separate conservation unit. We utilized nine microsatellites and 3 kb from four mitochondrial DNA (mtDNA) genes to estimate genetic variability, population structure, demographic parameters and visualize historic and contemporary connectivity among tiger populations from Sundarbans and mainland India. We also evaluated the traits that determine exchangeability or adaptive differences among tiger populations. Data from both markers suggest that Sundarbans tiger is not a separate tiger subspecies and should be regarded as Bengal tiger (P. t. tigris) subspecies. Maximum likelihood phylogenetic analyses of the mtDNA data revealed reciprocal monophyly. Genetic differentiation was found stronger for mtDNA than nuclear DNA. Microsatellite markers indicated low genetic variation in Sundarbans tigers (He= 0.58) as compared to other mainland populations, such as northern and Peninsular (Hebetween 0.67- 0.70). Molecular data supports migration between mainland and Sundarbans populations until very recent times. We attribute this reduction in gene flow to accelerated fragmentation and habitat alteration in the landscape over the past few centuries. Demographic analyses suggest that Sundarbans tigers have diverged recently from peninsular tiger population within last 2000 years. Sundarbans tigers are the most divergent group of Bengal tigers, and ecologically non-exchangeable with other tiger populations, and thus should be managed as a separate “evolutionarily significant unit” (ESU) following the adaptive evolutionary conservation (AEC) concept.
Highlights
Tiger (Panthera tigris) conservation remains an enormous challenge at both national and global scales and its long-term persistence depends on effective conservation and managementPLOS ONE | DOI:10.1371/journal.pone.0118846 April 28, 2015Sundarbans Tiger: A Separate Conservation Unit?strategies
In order to investigate if Sundarbans tigers have characteristics that distinguish them from other mainland tiger populations, Barlow et al [10] compared five tiger skulls from the Bangladesh Sundarbans with 175 skulls representing nine tiger subspecies
In order to investigate if Sundarbans tigers have characteristics that distinguish them from other mainland tiger populations, we examined a large sample of the published literature in order to find evidence of adaptive differences or traits, such as morphology, habitat type, size of prey, competition with other predators, tiger density [5, 8, 10, 68,69,70,71]
Summary
Tiger (Panthera tigris) conservation remains an enormous challenge at both national and global scales and its long-term persistence depends on effective conservation and managementPLOS ONE | DOI:10.1371/journal.pone.0118846 April 28, 2015Sundarbans Tiger: A Separate Conservation Unit?strategies. In order to investigate if Sundarbans tigers have characteristics that distinguish them from other mainland tiger populations, Barlow et al [10] compared five tiger skulls from the Bangladesh Sundarbans with 175 skulls representing nine tiger subspecies ( including three that are already extinct). They found that the skulls of Sundarbans tigers were smaller and significantly different from all other subspecies. Morphological distinctiveness of Sundarbans tigers raised questions regarding their conservation status Based on their results, the authors recommended that Sundarbans tigers should be managed separately and evaluated further to determine if they form an ESU
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