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Podocnemis lewyana is an endangered endemic river turtle of Colombia. Using ten unlinked polymorphic microsatellite loci and a 691-bp-long DNA fragment corresponding to the more variable portion of the mitochondrial control region, we investigated genetic diversity and population structure throughout its range. Both neutral markers showed extremely low diversity and weak population differentiation. Our data indicate that the genetic history of P. lewyana has been impacted by multiple bottlenecks and population expansion since the Pleistocene. The observed differentiation pattern is most likely the result of historically low genetic variation resulting from restricted geographic range and aggravated by recent anthropogenically induced bottlenecks. Based on slight differences in allele frequencies among populations, we suggest that three regions should be treated as demographically independent Management Units in order to preserve maximal genetic diversity: (1) the Upper Magdalena River Basin, (2) the Lower Magdalena ? Lower Cauca ? San Jorge River Basins, and (3) the Sinú River Basin. Among the Management Units, only low to moderate levels of gene flow were detected; these are largely unidirectional from Management Units 1 and 3 into Management Unit 2.Resumen Podocnemis lewyana es una tortuga endémica y amenazada de Colombia. Usando diez loci polimórficos de microsatélites y un fragmento de 691 pares de bases correspondiente a la porción más variable de la región control mitocondrial, investigamos la diversidad genética y estructura poblacional a través de su rango de distribución. Ambos marcadores neutrales revelaron una diversidad extremadamente baja y débil diferenciación poblacional. Nuestros datos indican que la historia genética de P. lewyana ha sido impactada por múltiples cuellos de botella y expansión poblacional desde el Pleistoceno. El patrón de diferenciación observado es más probable el resultado de la variación genética historica baja derivada del rango de distribución restringido, agravada por cuellos de botella recientes resultado de intervención antrópica. Basados en diferencias tenues de frecuencias alélicas entre poblaciones, sugerimos que tres regiones deben ser tratadas como Unidades de Manejo (UM) demográficamente independientes con el fin de preservar al máximo la diversidad genética. (1) Cuenca del alto río Magdalena, (2) Cuencas del bajo río Magdalena ? Bajo río Cauca ? río San Jorge, y (3) Cuenca del río Sinú. Entre las UM se detectaron niveles bajos a moderados de flujo genético que es principalmente unidireccional de las UM 1 y 3 a la UM 2.

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 first 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 five 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 five 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 fine-scale phylogeographic structures in this species.

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Mesoclemmys dahliandM. zuliaeare two endangered, little-known toad-headed turtles with small distribution ranges in Colombia and Venezuela, respectively. Using the mitochondrial cytochromebgene as a marker, we investigate their phylogeographic differentiation. Furthermore, based on 2341 bp of mtDNA and 2109 bp of nDNA ofM. dahli,M. zuliaeand allied chelid turtles, we infer their divergence time using a fossil-calibrated relaxed molecular clock approach.Mesoclemmys dahliandM. zuliaeare closely related species, with an estimated mean divergence time of 10.6 million years. This estimate correlates with the uplift of the Serranía de Perijá, an Andean mountain chain separating their distribution ranges, suggesting that this event could have caused the evolution of the two species. Haplotype and nucleotide diversities ofM. dahliare markedly higher than inPodocnemis lewyana, another endemic turtle species of Colombia. This pronounced dissimilarity may reflect differences in the phylogeographies and demographic histories of the two species, but also different habitat preferences.

Taxonomy. -Mesoclemmys dahli was originally described as Phrynops (Batrachemys) dahli by Zangerl and Medem in 1958, based on four specimens collected "near" Sincelejo, Sucre, Colombia. The epithet honors the collector, ichthyologist, and professor George Dahl from the Liceo Bolivar of Sincelejo. Medem (1966) later published data on the ecology and behavior of the species and provided information regarding its geographic range. Additionally, he collected a few more individuals that are deposited at the Instituto de Ciencias Naturales of the Universidad Nacional de Colombia.For many years the taxon was referred to as simply Phrynops dahli, as the use of subgenera did not gain wide acceptance. McCord et al. (2001) conducted a study of the broad genus Phrynops and suggested resurrecting and elevating the old subgenus Batrachemys, designating the species Batrachemys dahli. Their analyses were not accepted by some authors (Joyce et al. 2004 and others), mainly because the phylogenetic relationships of South American chelids are not well resolved, and the species was subsequently placed in the broader genus Mesoclemmys, also an old subgenus of Phrynops. Vargas-Ramírez et al. (2012) analyzed sequences of the mitochondrial cytochrome b gene and identified a close relationship and weak genetic divergence between M. dahli and M. zuliae from Venezuela. Currently, the Turtle Taxonomy Working Group (2012) recognizes the species as Mesoclemmys dahli.Description. -Mesoclemmys dahli is a small to medium-sized freshwater turtle. Maximum carapace length (CL) is 297 mm recorded from a female from Cesar. The species is characterized by having a proportionally large head with a pointed snout and a relatively thin and very long neck; tympanic head width is 23-26% of the carapace length (Rueda-Almonacid et al. 2007).