Mitochondrial DNA analysis reveals extremely low genetic diversity in a managed population of the Critically Endangered Gharial (Gavialis gangeticus, Gmelin, 1789)

Abstract

A decline in the numbers of threatened species is often reversed by reintroduction with the aim of repopulating or strengthening the population to reduce the risk of extinction. The success of reintroduction programs is associated with demographic and genetic monitoring of the reintroduced populations. We undertook a genetic assessment of the Critically Endangered gharial (Gavialis gangeticus) to assess the current level of genetic variation using three partial mitochondrial (mt) DNA regions: cytochrome b, cytochrome c oxidase subunit-I and the control region. We sequenced 103 samples collected across 14 nesting sites. A low level of mtDNA variation was observed in the sampled population (hd = 0.462 ± 0.048; Pi = 0.00029 ± 0.00004). Only five distinct haplotypes were observed in three segregating sites. This is the first assessment of the genetic variation in the wild gharial population to be made using mtDNA. Homogeneity in the 520 bp hypervariable control region of the crocodilian mtDNA is reported here for the first time. The low mitochondrial diversity and no genetic structure in the sampled population is indicative of a genetic bottleneck, the founder effect and probably associated with humanassisted augmentation of the population of the gharial. An extremely low level of genetic variation in the largest gharial population highlights the vulnerability of the gharial population in the wild and calls for immediate genetic assessment of other gharial populations so that a robust conservation plan focusing on connectivity and enhanced protection can be developed for the long-term persistence of the gharial in the wild.