Hope in the dark: discovery of a population related to the presumably extinct micro-endemic Blunt-headed Salamander (Ambystoma amblycephalum)

We report on the discovery of a population related to the Blunt-headed Salamander (Ambystoma amblycephalum), a micro-endemic axolotl from Mexico scientifically confirmed only once since its original description in 1940, and now presumably extinct. In 2018, paedomorphic and metamorphosed adults, as well as clutches and larvae, were found in a cattle pond at Nahuatzen, Michoacan state, Mexico, similar to 60 km away from the type locality (Tacicuaro). Morphometric comparisons suggested high similarity with the type series of A. amblycephalum, while mitochondrial DNA barcoding (16S and control region) revealed close (but imperfect) matching to a reference sequence. We gathered data on life history and ecology of this population, which could be the only extant relic of A. amblycephalum. Its highly limited distribution and presumably low population density are hallmarks for a high risk of extinction, and alarms on the critical situation of many micro-endemic salamanders of Mexico, hence calling for immediate conservation actions.

Automated summary

This study reports the discovery of a population related to the Blunt-headed Salamander, a micro-endemic axolotl from Mexico that has been scientifically confirmed only once since 1940 and is now presumed to be extinct. The population was found in a cattle pond in Michoacan state, Mexico, similar to 60 km away from the type locality. Morphometric comparisons suggested high similarity with the type series of A. amblycephalum, while mitochondrial DNA barcoding revealed close matching to a reference sequence. The highly limited distribution and presumably low population density of this population pose a high risk of extinction, emphasizing the urgent need for conservation actions.