Integrative reappraisal of the Amazonian nurse frog Allobates gasconi (Morales 2002) based on topotypical data, with implications for the systematics and taxonomy of a large species complex

Taxonomic uncertainty at the species level compromises our knowledge of biodiversity, conservation and systematics. The impact of such uncertainty is heightened in megadiverse regions such as Amazonia due to high levels of cryptic diversity. We used integrative taxonomy based on newly collected topotypical specimens to redescribe the Amazonian nurse frog Allobates gasconi and infer its phylogenetic relationships. This species was described in 2002 based solely on morphology, but several characters crucial for the reliable diagnosis of species in Allobates were not considered. Our results show that A. gasconi sensu stricto is not a member of the A. caeruleodactylus clade as previously claimed, but is a member of the A. trilineatus clade. Allobates gasconi is readily distinguished from congeners by a combination of morphological and bioacoustic characters; a revised diagnosis is provided. The type series of A. gasconi comprises more than one species, and we exclude a paratype from lower Jurua River. The species is restricted geographically to flooded environments in the middle and upper Jurua River in Brazil and in the Ucayali River in Peru. The initial misidentification, subsequent absence of topotypic molecular and acoustic data, and the poor preservation condition of the type series have contributed to taxonomic confusion since A. gasconi was first described. The descriptions of other species of Allobates published more than two decades ago were based mainly on gross morphology and we recommend integrative taxonomic revisions to elucidate their systematics.