Population genetics of the endangered South American freshwater turtle, Podocnemis unifilis, inferred from microsatellite DNA data

Abstract

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.

Extremely low genetic diversity and weak population differentiation in the endangered Colombian river turtle Podocnemis lewyana (Testudines: Podocnemididae)

“…Vargas-Ramírez et al (2007) studied a 488-bp-long fragment of the mitochondrial cytochrome b gene in 109 individuals from five regions in the Magdalena and Sinú River Basins and found only two haplotypes, differing by only one substitution. By contrast, in two other Podocnemis species high levels of genetic diversity were discovered with mtDNA and microsatellite data (Pearse et al 2006;Escalona et al 2009). In the present study, we use rapidly evolving nuclear and mitochondrial markers [microsatellites, variable part of the control region (CR)] and a range-wide sampling to assess population genetic structure, bottlenecks, gene flow, and population expansion in P. lewyana.…”

A Short Review of the International Trade of Wild Tortoises and Freshwater Turtles Across the World and Throughout Two Decades

“…reported possible occurrence in Trinidad and Tobago and introduced populations in Florida. Based on a study using microsatellites, Escalona et al (2009) suggested that the populations of the Amazon and Orinoco drainages represent genetically divergent lineages.…”

“…However, recent studies confirm a population decline. Escalona et al (2009) found genetic evidence of a "substantial recent population decline" in ten localities, and Escalona (2010) estimated that the populations had declined by at least 80 per cent during 2000-2010. Mittermeier et al (2010) noted that the species had disappeared from some beaches where it had previously nested.…”

Polymorphic microsatellite markers for the endangered fish, the slender shiner Pseudopungtungia tenuicorpa and cross-species amplification across five related species

“…A wild population of P. tenuicorpa in the Dal stream showed a higher average H E than those by R. ventralis (average 0.627) (Shao et al, 2015) and G. brevibarba (average 0.759) (Kim et al, 2014). These results suggest that the decline in wild populations of P. tenuicorpa is not the result of a decrease in genetic diversity but of human activities (Escalona et al, 2009). In addition, our results indicated that the genetic diversity of P. tenuicorpa was not significantly lower than that observed in other closely related species.…”