Species with highly restricted distributions are vulnerable to extinction, and modification of natural habitats within their small ranges is a primary threat to their persistence. Expansion of urban development significantly impacts natural habitats and, therefore, threatens local diversity. The Mexican axolotl, Ambystoma mexicanum
, is a strictly aquatic species that persists currently in two highly threatened and isolated populations. The current habitat remaining for these species are remnants of a historically extensive lacustrine system that occupied the entire Valley of Mexico, but has been destroyed by the growth of Mexico City. Unexpectedly, a third viable population of axolotls has been found in Chapultepec Park, a public recreational area in the heart of Mexico City.
Phylogenetic analyses of mitochondrial DNA sequences confirmed low genetic differentiation and a recurrent lack of monophyly in many of the taxa belonging to the Ambystoma tigrinum
species group, including A. mexicanum
, but clustered the Chapultepec samples with other A. mexicanum
samples. Our data revealed higher haplotypic diversity in A. mexicanum
populations than previously recorded, due to new haplotypes from Chapultepec Park. We found high incidence of parasites and deformities among individuals in this population, which could negatively impact their viability. Our results emphasize the important role that artificial or semi-natural urban habitats can play in the conservation of highly threatened species.
Maintenance of the Chapultepec population is an alternative to ex-situ conservation in aquaria and terrariums, and may offer benefits because individuals experience natural seasonal dynamics and breed naturally in the lakes. This semi-natural setting might prevent some of the negative effects of captivity, such as loss of fitness due to small breeding groups and artificial selection for traits favored in captivity. A healthy breeding population in Chapultepec would also facilitate future reintroduction programs and serve as a source of acclimatized animals. Finally, the location of the population and the number of visitors to Chapultepec provide a suitable environment for the development of conservation and educational programs. Green areas such as large urban parks can be of great conservation value as reserves for local biodiversity and for education of the public about environmental challenges facing local flora and fauna.