Biogeography of the Weakly Electric Knifefish Gymnotus carapo (Teleostei: Gymnotidae) in the Guianas

The electric knifefishes (Gymnotiformes) are widely distributed across South and Central America, with the highest species concentrations occurring in the Amazon and Orinoco basins. Riverine features such as waterfalls and rapids can cause disjunct populations to form between highland and lowland areas in these basins. The Guiana Shield provides a good model to study the genetic differences between populations precisely because it has upland and lowland areas with extant populations of Gymnotiformes. To examine genetic divergence between highlands and lowlands, mitochondrial (cytochrome b) and nuclear (S7) DNA was sequenced for members of the Gymnotus carapo species complex (Gymnotidae). Population and phylogenetic analysis indicate a distinct split between upland and lowland populations, with those species in the highlands showing greater genetic similarity to populations from the Amazon basin.M.Sc