Abstract
We report on a discovery of Siamophryne troglodytes Gen. et sp. nov., a new troglophilous genus and species of microhylid frog from a limestone cave in the tropical forests of western Thailand. To assess its phylogenetic relationships we studied the 12S rRNA–16S rRNA mtDNA fragment with final alignment comprising up to 2,591 bp for 56 microhylid species. Morphological characterization of the new genus is based on examination of external morphology and analysis of osteological characteristics using microCT-scanning. Phylogenetic analyses place the new genus into the mainly Australasian subfamily Asterophryinae as a sister taxon to the genus Gastrophrynoides, the only member of the subfamily known from Sundaland. The new genus markedly differs from all other Asterophryinae members by a number of diagnostic morphological characters and demonstrates significant mtDNA sequence divergence. We provide a preliminary description of a tadpole of the new genus. Thus, it represents the only asterophryine taxon with documented free-living larval stage and troglophilous life style. Our work demonstrates that S. troglodytes Gen. et sp. nov. represents an old lineage of the initial radiation of Asterophryinae which took place in the mainland Southeast Asia. Our results strongly support the “out of Indo-Eurasia” biogeographic scenario for this group of frogs. To date, the new frog is only known from a single limestone cave system in Sai Yok District of Kanchanaburi Province of Thailand; its habitat is affected by illegal bat guano mining and other human activities. As such, S. troglodytes Gen. et sp. nov. is likely to be at high risk of habitat loss. Considering high ecological specialization and a small known range of the new taxon, we propose a IUCN Red List status of endangered for it.
Highlights
Microhylidae is one of the largest frog families belonging to the Ranoidea, with a pantropical distribution
Sequence variation The studied 12S rRNA–16S rRNA mtDNA fragment consisted of 2,591 sites: 1,070 sites were conserved and 1,394 sites were variable, 1,070 of which were found to be parsimonyinformative
Systematics and biogeography In the present paper, we report a new lineage of Asterophryinae microhylid frogs from western Thailand, Tenasserim region of mainland Southeast Asia
Summary
Microhylidae is one of the largest frog families belonging to the Ranoidea, with a pantropical distribution. To date, it includes 641 species (nearly 9.4% of anuran diversity) (Frost, 2017). Family-level taxonomy of Microhylidae is considered to be a “phylogeneticist’s nightmare” (Peloso et al, 2016) and is the subject of numerous studies and an ongoing debate. The degree of coherence between the morphological and molecular classifications of the family is quite low due to the high morphological variation and widespread convergence in microhylids, which, in many cases, likely is connected to specializations associated with a burrowing lifestyle (see de Saet al., 2012; Peloso et al, 2016). The basal split within Microhylidae is estimated to coincide with the Cretaceous–Paleogene boundary (65 Ma) (Feng et al, 2017); previous studies argued for Mesozoic origin of Microhylidae and considered the constituent subfamilies as full families of Anura (Bossuyt & Roelants, 2009)
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