New populations of two threatened species of Alsodes (Anura, Alsodidae) reveal the scarce biogeographic knowledge of the genus in the Andes of central Chile

摘要

High Andean environments of central Chile (32°–38°S) are inhabited by several endemic species of the genus Alsodes. Two of them, A. pehuenche and A. hugoi, have geographic distributions restricted to their type locality and surroundings. The Chilean government classifies A. pehuenche as Critically Endangered (like the IUCN) and A. hugoi as Vulnerable. In this study we report 16 new localities of Alsodes, corresponding to first order streams, located in the Andes of Chile between 35°58’ and 36°32’S (1800–2470 m). In some of these sites, adults and juveniles morphologically similar to A. pehuenche and A. hugoi were observed, as well as specimens of Alsodes that could not be identified by their external morphology. A Bayesian phylogenetic analysis with mitochondrial sequences (cytochrome b) was performed to identify the new populations to species level. All populations around 36°S belong to A. pehuenche, while most of those located south of that area would be A. hugoi. The exception is Cajón de Plaza (36°23’S), where specimens with sequences of A. hugoi or A. pehuenche coexist, whose taxonomic status could not be determined. These findings imply not only a westward range extension of A. pehuenche in Chile of about 14.5 km and of A. hugoi about 100 km southward, but also that practically all the first order streams of the Andes of central Chile would be inhabited by populations of Alsodes. Both results demonstrate the scarce biogeographic knowledge of the genus in the Andes, which has important implications for its conservation at local and species levels.