Integrating genomic and vocal evidence to reassess species’ limits and the biogeography of a widely distributed Neotropical passerine, the white-throated spadebill, <i>Platyrinchus mystaceus</i> (Aves: Platyrhinchidae)

Abstract The white-throated spadebill (Platyrinchus mystaceus) is a small passerine with a circum-Amazonian distribution from Costa Rica to southern Brazil. Despite its broad range, the evolutionary processes driving population differentiation remain unclear, and its taxonomy has not been assessed using modern molecular data. Traditionally treated as a single species with at least 14 subspecies, some classifications separate eastern (P. mystaceus) and western (P. albogularis) forms, while recent data suggest three genetically distinct clusters. We integrated genetic data and song recordings to assess species’ limits in the P. mystaceus complex. We analysed population structure, phylogeographic relationships, and evolutionary processes underlying divergence. Vocalizations were examined for correspondence with genetic clusters. Our analyses identified three genetic clusters: (i) north-eastern Atlantic Forest in Brazil; (ii) southern/central Atlantic Forest, northern Brazil, Guiana Shield, and the Caribbean; and (iii) Central America, Chocó region, and the Andes. Genetic admixture was detected in Bolivia. Demographic analyses support vicariant divergence with post-divergence migration. Divergence occurred during the Calabrian and Middle Pleistocene, highlighting the role of Quaternary climate changes. Song types aligned with genetic clusters. Genetic and vocal analyses support recognizing three species: P. mystaceus, P. albogularis, and P. niveigularis, the latter representing an independent evolutionary lineage in north-eastern Brazil.