Taxonomic reappraisal of the northeast Mindanao Stream Frog, Sanguirana albotuberculata (Inger 1954), validation of Rana mearnsi, Stejneger 1905, and description of a new species from the central Philippines

With a published multilocus phylogenetic analysis as our guide, we use new data from the external phenotype and genetically defined distributions of evolutionary lineages to resolve species boundaries associated with the southwest Mindanao Stream Frogs, Sanguirana everetti (Boulenger 1882), its junior synonym, Rana mearnsi, Stejneger 1905, and the northeast Mindanao Stream Frogs, Sanguirana albotuberculata (Inger 1954). Consideration of relationships, distributions, type localities, phenotypic data, and type specimens clearly indicates that the names R. mearnsi and S. albotuberculata refer to the same lineage, and we recognize the oldest available name (Sanguirana mearnsi) for this species. We also define the central Philippine lineage (from Negros, Masbate, and Panay islands) as a distinct new species. Long confused with S. everetti, the new taxon is readily diagnosed and biogeographically restricted to the West Visayan faunal region. The new multilocus estimate of phylogeny and our multivariate analysis of morphological variation demonstrate that the new species is closely related and phenotypically most similar to northern Philippine Sanguirana luzonensis, to the exclusion of S. everetti, the southern species with which it previously was confused. Morphological characters distinguishing the new species include body size, the absence of infracloacal tubercles, the presence of smooth dorsal skin without dorsolateral folds or dermal asperities, its degree of sexual size dimorphism, uniquely stratified flank coloration, bright white subarticular tubercles, bold pectoral patches, dark transverse bars on the limbs, and various body proportions. Recognition of this new species further emphasizes the predictable nature of island bank-structured endemism in the Philippines and demonstrates that the country’s vertebrate diversity remains underestimated. The new species is relatively rare, patchily distributed and, with so little natural forest remaining in the central Philippines, it constitutes an immediate conservation concern. Management of this problem will require continued, field-based collection of data on the new species, distribution, local abundance, population trends, natural history, reproductive biology, and larval ecology—most of which currently is unknown.