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<p>Turtles represent one of the most imperilled groups of organisms on earth, with approximately 40% of the world’s existing turtle species facing the risk of extinction due to various anthropogenic factors. The northern river terrapin (<i>Batagur baska</i>), a critically endangered species belonging to the Geoemydidae family, is currently limited to the Sundarbans in India and Bangladesh. <i>B. baska</i> has been wiped out from much of its former habitat, with no known wild populations remaining. Captive breeding programs were initiated at the Sajnekhali range station within the Sundarbans Tiger Reserve to bolster dwindling populations. Until now, no genetic data have been available for the last remaining population of <i>B. baska</i> in the Sundarbans, India. In this study, we sequenced and characterized the mitogenome of <i>B. baska</i> (~ 16,280&#xa0;bp) to explore the gene arrangements and phylogenetic relationships with other Testudines and gain insights into the adaptive evolution of mitochondrial protein-coding genes. Furthermore, we examined genetic diversity and population demography using the mtDNA control region (CR: ~747&#xa0;bp) for <i>B. baska</i> and compared the diversity with other endangered Batagur species. The data revealed the presence of 5 haplotypes in 22 sequences, indicating low levels of nucleotide diversity (π = 0.0012). Phylogenetic analyses using mitogenome (except control region) produce a well-supported genetic relationship with high posterior probability (PP ~ 0.99) between the Northern (<i>B. baska</i>) and Southern (<i>B. affinis</i>) river terrapins followed by <i>B. kachuga</i>. Population demography analysis suggested a declining trend from the late Pleistocene to the Last Glacial Maximum. Considering the ongoing in-situ breeding programs, we suggest to expand this program and continue reinforcement and integration with translocation to mitigate the impact of the low nucleotide and limited population size. These measures are crucial for preserving the genetic diversity and conservation of the critically endangered <i>B. baska</i>. Further, we emphasize the need for extensive research by incorporating microsatellite analysis or whole genome sequencing to gain for deep insight into the genetic status of <i>B. baska</i> in the Sundarbans.</p>

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Unveiling the contemporary genetic diversity and population demography of the critically endangered northern river terrapin (Batagur baska) in the sundarbans

  • 期刊论文

  • 发表日期：

    2025年11月5日

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  • Ajit Kumar,
  • Anand Sharma,
  • Naveen Negi,
  • Ruchi Badola,
  • Syed Ainul Hussain,
  • Sandeep Kumar Gupta

摘要

Turtles represent one of the most imperilled groups of organisms on earth, with approximately 40% of the world’s existing turtle species facing the risk of extinction due to various anthropogenic factors. The northern river terrapin (Batagur baska), a critically endangered species belonging to the Geoemydidae family, is currently limited to the Sundarbans in India and Bangladesh. B. baska has been wiped out from much of its former habitat, with no known wild populations remaining. Captive breeding programs were initiated at the Sajnekhali range station within the Sundarbans Tiger Reserve to bolster dwindling populations. Until now, no genetic data have been available for the last remaining population of B. baska in the Sundarbans, India. In this study, we sequenced and characterized the mitogenome of B. baska (~ 16,280 bp) to explore the gene arrangements and phylogenetic relationships with other Testudines and gain insights into the adaptive evolution of mitochondrial protein-coding genes. Furthermore, we examined genetic diversity and population demography using the mtDNA control region (CR: ~747 bp) for B. baska and compared the diversity with other endangered Batagur species. The data revealed the presence of 5 haplotypes in 22 sequences, indicating low levels of nucleotide diversity (π = 0.0012). Phylogenetic analyses using mitogenome (except control region) produce a well-supported genetic relationship with high posterior probability (PP ~ 0.99) between the Northern (B. baska) and Southern (B. affinis) river terrapins followed by B. kachuga. Population demography analysis suggested a declining trend from the late Pleistocene to the Last Glacial Maximum. Considering the ongoing in-situ breeding programs, we suggest to expand this program and continue reinforcement and integration with translocation to mitigate the impact of the low nucleotide and limited population size. These measures are crucial for preserving the genetic diversity and conservation of the critically endangered B. baska. Further, we emphasize the need for extensive research by incorporating microsatellite analysis or whole genome sequencing to gain for deep insight into the genetic status of B. baska in the Sundarbans.