Genetic Variability in the Magdalena River Turtle, Podocnemis Lewyana (Duméril, 1852), in the Mompos Depression, Colombia (original) (raw)
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DOAJ (DOAJ: Directory of Open Access Journals), 2008
Two populations of the endangered Magdalena River turtle, Podocnemis lewyana, separated by 55 km in the Mompos Depression were sampled to quantify levels of genetic variation and inspect for evidence of genetic structure. Allozyme analyses resolved 22 presumptive gene loci, but only one resulted polymorphic. Genotype proportions at this locus departed from those expected under Hardy-Weinberg equilibrium, showing heterozygote deficiencies in both populations. However, allele frequencies at the locus did not differ between the two sites. The level of genetic variability documented is one of the lowest yet reported for a turtle species, and may reflect either a historical or recent bottleneck event. The lack of evidence for genetic structure suggests gene flow among the sites, at least historically, but the heterozygote deficiencies at each site also imply that inbreeding may be occurring presently within each deme.
Two populations of the endangered Magdalena River turtle, Podocnemis lewyana, separated by 55 km in the Mompos Depression were sampled to quantify levels of genetic variation and inspect for evidence of genetic structure. Allozyme analyses resolved 22 presumptive gene loci, but only one resulted polymorphic. Genotype proportions at this locus departed from those expected under Hardy-Weinberg equilibrium, showing heterozygote deficiencies in both populations. However, allele frequencies at the locus did not differ between the two sites. The level of genetic variability documented is one of the lowest yet reported for a turtle species, and may reflect either a historical or recent bottleneck event. The lack of evidence for genetic structure suggests gene flow among the sites, at least historically, but the heterozygote deficiencies at each site also imply that inbreeding may be occurring presently within each deme.
Contributions to …, 2007
The Magdalena River Turtle (Podocnemis lewyana) is a Colombian endemic species, endangered due to human exploitation and habitat destruction. To date, this species is poorly known ecologically and data on its genetic diversity are lacking. Here we report on the fi rst genetic survey of the species across its distribution range. We obtained mitochondrial DNA sequences (488 bp) of the cytochrome b gene from 109 individuals. Samples belong to populations located at several different localities, grouped in fi ve regions, along the four main river basins: Magdalena, Cauca, San Jorge, and Sinú drainages. We found two haplotypes, which differ in only one nucleotide substitution and which are represented with different frequencies in the fi ve geographic regions. These results suggest that P. lewyana harbors little genetic variation and is a genetically uniform species, but more variable markers (i.e., microsatellites) should be used to unravel fi ne-scale phylogeographic structures in this species.
2008
We studied the population genetics of Podocnemis unifilis turtles within and among basins in the Orinoco and Amazon drainages using microsatellites. We detected high levels of genetic diversity in all sampled localities. However, 'M-ratio' tests revealed a substantial recent population decline in ten localities, in accord with current widespread exploitation. Our results reveal a consistent pattern across multiple analyses, showing a clear subdivision between the populations inhabiting the Amazon and Orinoco drainages despite a direct connection via the Casiquiare corridor, and suggesting the existence of two biogeographically independent and widely divergent lineages. Genetic differentiation followed an isolationby-distance model concordant with hypotheses about migration. It appears that migration occurs via the flooded forest in some drainages, and via river channels in those where geographic barriers preclude dispersal between basins or even among nearby tributaries of the same basin. These observations caution against making generalizations based on geographically restricted data, and indicate that geographically proximate populations may be demographically separate units requiring independent management.
Podocnemis sextuberculata (Pleurodira: Podocnemididae) is widely distributed throughout the Amazon drainage basin in Brazil, Colombia, and Peru. Telemetry and previous molecular data suggest that P. sextuberculata lacks population structure in the central Amazon basin of Brazil. Generalization of these results, however, requires much-broader sampling across a range of habitats of this broadly distributed species. For this reason, we tested the hypothesis of panmixia in P. sextuberculata, analyzing a total of 319 specimens sequenced for the mitochondrial control region. Our sampling included localities from 16 areas in the Amazon basin from rivers characteristic of the Amazon basin (whitewater), clearwater rivers of the Guiana shield (Branco, Trombetas, and Nhamund´a rivers), and the Brazilian shield (Xingu River). The hypothesis of panmixia was rejected because the results of analysis of molecular variance, pairwise VST, and Bayesian analysis of population structure indicated population structure in the group of individuals from the locality of Xingu which was not correlated to a pattern of isolation by distance. We suggest that the populations of P. sextuberculata of the Brazilian Amazon basin are composed of 2 management units, one represented by populations restricted to the Xingu River and the other represented by all other populations. The population of the Xingu should be viewed with attention and concern, especially considering the direct and indirect impacts of damming the Xingu River.
ContextWaterfalls and rapids of Amazon basin have been suggested as causing the speciation and genetic structure of many freshwater species, including turtles. The species behavior affects the way waterfalls and rapids limit gene flow. The Yellow-spotted River Turtle (Podocnemis unifilis), a widely distributed and endangered Amazonian turtle, does not show the habit to migrate long distances for breeding or eating, but has a complex geographic pattern of genetic variation.ObjectivesHere, we investigate isolation by distance and by resistance of P. unifilis. We analyzed if the species ecological niche and waterfalls explain the genetic distance in Brazilian Amazonia.MethodsWe evaluated the P. unifilis spatial distribution of genetic variability and diversity using the control region of mitochondrial DNA. We tested the hypotheses of isolation either by distance and resistance through an integrative approach using genetic, geographic, and ecological data. We created a resistance matrix...
Mitochondrial DNA, 2012
We present a mtDNA analysis of Podocnemis expansa (n ¼ 81) and Podocnemis unifilis (n ¼ 228) turtles traded in Peru to evaluate the potential origin of these animals. In particular, we were interested in the relationship between samples reported in the Iquitos markets (IMs) and a Pacaya Samiria Natural Reserve (PSNR) where illegal hunting is presumed. Our mtDNA data showed that, for both species, all haplotypes found within the PSNR were observed in the IM, and that these markets also displayed haplotypes not documented in the reserve. This suggests that the IMs are recipients of Podocnemis turtles from within and outside the PSNR. The fact that most of the haplotype diversity observed in the markets was not found within the PSNR strongly suggests that Podocnemis genetic diversity is exploited in areas where conservation actions are limited. Hence, we recommend expanding Podocnemis conservation efforts outside of protected areas.
Stand out from the Crowd: Small-Scale Genetic Structuring in the Endemic Sicilian Pond Turtle
Diversity
The geographical pattern of genetic diversity was investigated in the endemic Sicilian pond turtle Emys trinacris across its entire distribution range, using 16 microsatellite loci. Overall, 245 specimens of E. trinacris were studied, showing high polymorphic microsatellite loci, with allele numbers ranging from 7 to 30. STRUCTURE and GENELAND analyses showed a noteworthy, geographically based structuring of the studied populations in five well-characterized clusters, supported by a moderate degree of genetic diversity (FST values between 0.075 and 0.160). Possible explanations for the genetic fragmentation observed are provided, where both natural and human-mediated habitat fragmentation of the Sicilian wetlands played a major role in this process. Finally, some conservation and management suggestions aimed at preventing the loss of genetic variability of the species are briefly reported, stressing the importance of considering the five detected clusters as independent Management U...
Frontiers in Ecology and Evolution, 2021
Marine turtle nesting areas are characterized by receiving several females every year. The species Eretmochelys imbricata, known as hawksbill turtle is listed as Critically Endangered by the IUCN, and has been the target of studies on genetic structure and population diversity in nesting areas. Therefore, this study aimed to analyze the genetic diversity and haplotype composition of populations sampled in nesting areas from the coast of northeastern Brazil based on the mtDNA D-loop region. We used genetic information and compared it with data from feeding areas available in public databases. We recorded a total of six exclusive haplotypes in the nesting areas and 27 exclusive haplotypes for the feeding areas. The H_1 haplotype was shared in all nesting areas. The turtles of these regions had a low diversity and a genetic structure composed of five divergent groups separating the reproductive areas from the ones of feeding areas. Positive and significant geographical distance relatio...