An isolated population of Austrolebias charrua (Rivulidae, Cyprinodontiformes) detected in a fragile ecosystem (Maldonado, Uruguay)

Annual killifishes inhabit seasonal ponds and wetlands that dry out completely during the dry season, and tend to present very restricted distributions, meaning that local extinctions can lead to the disappearance of entire populations. Using morphological and genetic approaches the present study identifies a new population of Austrolebias charrua in an isolated area of the lower basin of Maldonado stream (Atlantic Ocean coastal basin) in Uruguay. The new population extends the previous area of occurrence by 20 km(2), 100 km to the south of previous records, and shows some genetic and morphological characteristics that indicate it is isolated from other populations in the previously known range. This species has been catalogued as a priority for conservation by the National System of Protected Areas of Uruguay; the new record does not significantly affect the size of the area of occupation of the species. The new site, located in the Alameda de San Carlos, is a small area that suffers human threats that may lead to environmental impacts and thus jeopardize the conservation of this population.