A New Species of Terrestrial Foam-Nesting Frog (Adenomera, Leptodactylidae) from the Várzea Forests of Western Amazonia

Cryptic diversity within species poses a challenge to traditional taxonomy, often leading to underestimation of species richness and incorrect assessments of extinction risks. The taxonomy of Adenomera frogs has greatly benefited from the integrated assessment of morphological, acoustic, and DNA sequence data. Here we address a taxonomic problem by analyzing the external morphology, color patterns, advertisement calls, and genetic variation of one of the nine molecular lineages of the Adenomera simonstuarti species complex, distributed in western Amazonia. Based on novel data from the upper Juruá River, in northwestern Brazil and Ecuador, we found that this lineage exhibits significant differences in morphology (body size), coloration (absence of a solid stripe on the ventral surface of the forearm), and calls (nonpulsed and formed by a single type of note) in comparison with congeners. This combination of phenotypic traits supports the taxonomic distinction of this lineage, which is formally described as a new species. Interestingly, the new species uses várzea (seasonally flooded) forests as its calling and breeding habitat, a unique feature among forest-dwelling Amazonian species of the genus, which are always associated with terra firme (non-flooded) forests. This study reinforces the relevance of acoustic mating signals combined with DNA sequences in uncovering new species, contributing to a better understanding of the anuran diversity in Amazonia.