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

ABSTRACT 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, Michoacán state, Mexico, ~60 km away from the type locality (Tacícuaro). 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.