Microsatellite DNA is among the several molecular tools used for determining genetic variability ... more Microsatellite DNA is among the several molecular tools used for determining genetic variability and inbreeding depression in threatened populations. It has been used extensively for population genetics studies in conservation of crocodilians. Even though single nucleotide polymorphisms have higher precision compared to microsatellite DNA markers, microsatellites offer a cost advantage which is particularly important to researchers in the global south. Here, we review the role of microsatellite DNA as a conservation tool in crocodilians. Employing appropriate keywords in three online databases, we studied 78 publications, where microsatellite DNA had been used to study crocodilian species. We found that 504 species-specific markers were designed for 13, out of a total of 24 crocodilian taxa. Genus Crocodylus had the highest number of species-specific markers and was the most studied taxa using microsatellites. Moreover, microsatellite markers developed for C. porosus were successful in cross amplification of microsatellite markers in 19 other crocodilian species. Microsatellite based studies had highest focus on analyses of multiple populations of a single species. Based on our review of microsatellite based studies on populations of crocodilian species, we recommend that microsatellite DNA markers are an effective conservation tool that can provide critical information on population structures of threatened crocodilian species.
The gharial Gavialis gangeticus (Gmelin, 1789) is a critically endangered crocodile, endemic to t... more The gharial Gavialis gangeticus (Gmelin, 1789) is a critically endangered crocodile, endemic to the Indian sub-continent (Lang et al., 2019). The global gharial population size has shown an increasing trend in recent years, with the number of adult individuals estimated to be 650 (range 300-900; Lang et al., 2019). However, habitat alteration and fragmentation caused by damming, as well as rising pressures such as illicit sand mining and fishing, remain a risk for the survival of the species in the wild (
The gharial (<i>Gavialis gangeticus</i>) is a critically endangered, long-snouted cro... more The gharial (<i>Gavialis gangeticus</i>) is a critically endangered, long-snouted crocodylian, endemic to the Indian sub-continent. Today, the species' distribution and numbers have reduced by >95% in all the large rivers where it was formerly abundant. Living upstream in a reservoir dammed in 1976, the Katerniaghat gharial population has continued to nest along the Girwa River, subject to seasonal flooding in recent decades. In 2010, a natural flood upstream in Nepal, resulted in a permanent reduction in the mainstream river flow. As a consequence, the formerly open sand banks and mid river islands have converted gradually to riverbanks with woody vegetation in years subsequent to the flood. Coincident with the increased vegetation growth, gharial nesting sites and nest numbers declined by >40% by 2018. In an attempt to reverse the observed decline in nesting, we intervened with vegetation removal (VR) in 2019 and sand addition (SA) in 2020, to augment availab...
Gharial (Gavialis gangeticus) is a critically endangered fresh water crocodile endemic to the Ind... more Gharial (Gavialis gangeticus) is a critically endangered fresh water crocodile endemic to the Indian subcontinent. The species has suffered > 95% decline in population and habitat size. A small population of gharials comprising of 50 breeding adults is resident in a 20 Km stretch of the River Girwa in Katerniaghat wildlife sanctuary, India. Gharials in this 20 Km stretch have been genetically isolated since 1976 by a barrage that functions as a barrier to gene flow. A captive rear and release program has been initiated since 1979 under Project Crocodile for restocking declining wild gharial populations. Thousands of gharial eggs were collected from gharial populations at Girwa and Chambal Rivers. Hatchlings from the collected eggs were captive reared at a common location in Kukrail Gharial Centre, India and released back to multiple gharial populations including the isolated population at Girwa. This restocking programme was not preceded by a genetic screening of captive animals ...
The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to sout... more The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverbank of the Girwa River. A natural channel shift in the mainstream Karnali River (upstream in Nepal) has reduced seasonal flow in the Girwa stretch where gharials nest, coincident with a gradual loss of nest sites, which in turn was related to an overall shift to woody vegetation at these sites. To understand how these changes in riparian vegetation on riverbanks were related to gharial nesting, we sampled vegetation at these sites from 2017 to 2019, and derived an Enhanced Vegetation Index (EVI) from LANDSAT 8 satellite data to quantify riverside vegetation from 1988 through 2019. We found that sampled sites transitioned to woody cover, the ...
The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to sout... more The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverbank of the Girwa River. A natural channel shift in the mainstream Karnali River (upstream in Nepal) has reduced seasonal flow in the Girwa stretch where gharials nest, coincident with a gradual loss of nest sites, which in turn was related to an overall shift to woody vegetation at these sites. To understand how these changes in riparian vegetation on riverbanks were related to gharial nesting, we sampled vegetation at these sites from 2017 to 2019, and derived an Enhanced Vegetation Index (EVI) from LANDSAT 8 satellite data to quantify riverside vegetation from 1988 through 2019. We found that sampled sites transitioned to woody cover, the ...
Microsatellite DNA is among the several molecular tools used for determining genetic variability ... more Microsatellite DNA is among the several molecular tools used for determining genetic variability and inbreeding depression in threatened populations. It has been used extensively for population genetics studies in conservation of crocodilians. Even though single nucleotide polymorphisms have higher precision compared to microsatellite DNA markers, microsatellites offer a cost advantage which is particularly important to researchers in the global south. Here, we review the role of microsatellite DNA as a conservation tool in crocodilians. Employing appropriate keywords in three online databases, we studied 78 publications, where microsatellite DNA had been used to study crocodilian species. We found that 504 species-specific markers were designed for 13, out of a total of 24 crocodilian taxa. Genus Crocodylus had the highest number of species-specific markers and was the most studied taxa using microsatellites. Moreover, microsatellite markers developed for C. porosus were successful in cross amplification of microsatellite markers in 19 other crocodilian species. Microsatellite based studies had highest focus on analyses of multiple populations of a single species. Based on our review of microsatellite based studies on populations of crocodilian species, we recommend that microsatellite DNA markers are an effective conservation tool that can provide critical information on population structures of threatened crocodilian species.
The gharial Gavialis gangeticus (Gmelin, 1789) is a critically endangered crocodile, endemic to t... more The gharial Gavialis gangeticus (Gmelin, 1789) is a critically endangered crocodile, endemic to the Indian sub-continent (Lang et al., 2019). The global gharial population size has shown an increasing trend in recent years, with the number of adult individuals estimated to be 650 (range 300-900; Lang et al., 2019). However, habitat alteration and fragmentation caused by damming, as well as rising pressures such as illicit sand mining and fishing, remain a risk for the survival of the species in the wild (
The gharial (<i>Gavialis gangeticus</i>) is a critically endangered, long-snouted cro... more The gharial (<i>Gavialis gangeticus</i>) is a critically endangered, long-snouted crocodylian, endemic to the Indian sub-continent. Today, the species' distribution and numbers have reduced by >95% in all the large rivers where it was formerly abundant. Living upstream in a reservoir dammed in 1976, the Katerniaghat gharial population has continued to nest along the Girwa River, subject to seasonal flooding in recent decades. In 2010, a natural flood upstream in Nepal, resulted in a permanent reduction in the mainstream river flow. As a consequence, the formerly open sand banks and mid river islands have converted gradually to riverbanks with woody vegetation in years subsequent to the flood. Coincident with the increased vegetation growth, gharial nesting sites and nest numbers declined by >40% by 2018. In an attempt to reverse the observed decline in nesting, we intervened with vegetation removal (VR) in 2019 and sand addition (SA) in 2020, to augment availab...
Gharial (Gavialis gangeticus) is a critically endangered fresh water crocodile endemic to the Ind... more Gharial (Gavialis gangeticus) is a critically endangered fresh water crocodile endemic to the Indian subcontinent. The species has suffered > 95% decline in population and habitat size. A small population of gharials comprising of 50 breeding adults is resident in a 20 Km stretch of the River Girwa in Katerniaghat wildlife sanctuary, India. Gharials in this 20 Km stretch have been genetically isolated since 1976 by a barrage that functions as a barrier to gene flow. A captive rear and release program has been initiated since 1979 under Project Crocodile for restocking declining wild gharial populations. Thousands of gharial eggs were collected from gharial populations at Girwa and Chambal Rivers. Hatchlings from the collected eggs were captive reared at a common location in Kukrail Gharial Centre, India and released back to multiple gharial populations including the isolated population at Girwa. This restocking programme was not preceded by a genetic screening of captive animals ...
The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to sout... more The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverbank of the Girwa River. A natural channel shift in the mainstream Karnali River (upstream in Nepal) has reduced seasonal flow in the Girwa stretch where gharials nest, coincident with a gradual loss of nest sites, which in turn was related to an overall shift to woody vegetation at these sites. To understand how these changes in riparian vegetation on riverbanks were related to gharial nesting, we sampled vegetation at these sites from 2017 to 2019, and derived an Enhanced Vegetation Index (EVI) from LANDSAT 8 satellite data to quantify riverside vegetation from 1988 through 2019. We found that sampled sites transitioned to woody cover, the ...
The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to sout... more The gharial (Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverbank of the Girwa River. A natural channel shift in the mainstream Karnali River (upstream in Nepal) has reduced seasonal flow in the Girwa stretch where gharials nest, coincident with a gradual loss of nest sites, which in turn was related to an overall shift to woody vegetation at these sites. To understand how these changes in riparian vegetation on riverbanks were related to gharial nesting, we sampled vegetation at these sites from 2017 to 2019, and derived an Enhanced Vegetation Index (EVI) from LANDSAT 8 satellite data to quantify riverside vegetation from 1988 through 2019. We found that sampled sites transitioned to woody cover, the ...
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