Morphology, phylogeny, and species delimitation of Micryletta (Anura: Microhylidae) reveals a new species from Singapore

The genus Micryletta, also known as paddy frogs, ranges across much of south, east, and southeast Asia. Due to their relatively broad distribution and overall morphological similarities, many species have gone undetected until recently, largely owing to the use of molecular data. Consequently, the species diversity within this genus has quadrupled in just three years from three species prior to 2018, to 12 species in 2021, indicating that the systematics of this genus is still poorly understood. As such, we assembled the most comprehensive molecular phylogeny of Micryletta hitherto including novel sequences from a previously unsampled population from Singapore to assess the species diversity within this genus. In particular, we investigate the population from Singapore whose specific identity remains in question due to the lack of voucher specimens and genetic material. Our results show that the Singapore population represents a strongly supported and distinct lineage that is most closely related to M. inornata sensu stricto from Sumatra, Indonesia. Morphological and species delimitation analyses corroborate its distinction as a new species, which we describe herein as M. subaraji sp. nov. This and recent new taxon discoveries in Singapore demonstrate that the biodiversity of the highly urbanized island-state is still far from being fully realized and underscores the need for continued systematic surveys and protection of remaining habitats.