Unearthing the names of burrowing frogs: The taxonomic status of the Chacoan populations of Leptodactylus fuscus (Schneider, 1799) (Anura: Leptodactylidae)

Abstract The widely distributed Neotropical frog Leptodactylus fuscus has long been suspected to represent a species complex. Among its numerous synonyms is Leptodactylus gualambensis Gallardo, 1964, described based on specimens from the western South American Gran Chaco and regarded as a typical Chacoan species. This species was synonymized 40 years ago and has not been reassessed since. In this study, we evaluate the taxonomic validity of the Chacoan populations of L. fuscus potentially assignable to L. gualambensis , based on molecular phylogenetic analyses, lineage delimitation, bioacoustics, and morphology using extensive sampling from the South American Gran Chaco and adjacent regions. Our phylogenetic analyses revealed three clades: One distributed across northern South America and Central America, including topotypes of L. fuscus ; a second primarily occurring in the South American Gran Chaco, including topotypes of L. gualambensis ; and a third found in parts of Paraguay, Argentina, and Brazil. This structure is corroborated by lineage delimitation analysis, genetic differentiation, gene flow estimations, and by differences in advertisement call duration and frequency, as well as head and limb proportions. Based on these results, we support the revalidation of L. gualambensis , redefine the geographic distribution of L. fuscus sensu stricto, and discuss the status of other available synonyms. In addition, we discuss variation in certain morphological traits of L. gualambensis that may be associated with its broad geographic distribution, which encompasses both dry, highly seasonal environments and humid, relatively homogeneous habitats.