A striking new genus and species of cave-dwelling frog (Amphibia: Anura: Microhylidae: Asterophryinae) from Thailand

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.

A new limestone-dwelling species ofMicryletta(Amphibia: Anura: Microhylidae) from northern Vietnam

“…The complex terrain of isolated karstic hills and caves create multiple ecological niches what along with their highly fragmented habitat-island nature result in high degrees of site-specific endemism within, and diversity among them ( Oliver et al, 2017 ; Grismer et al, 2018 ). Limestone karsts are also known as important “biodiversity arks” for both surface and cave faunas, yet karstic regions are rapidly becoming some of the most imperiled ecosystems on the planet ( Clements et al, 2006 ; Grismer et al, 2016a , 2016b , 2018 ; Luo et al, 2016 ; Suwannapoom et al, 2018 ). South-east Asia harbors more limestone karsts than anywhere else on earth ( Day & Urich, 2000 ) with numerous new species including relic lineages of amphibians and reptiles being discovered from limestone areas (e.g.…”

“…South-east Asia harbors more limestone karsts than anywhere else on earth ( Day & Urich, 2000 ) with numerous new species including relic lineages of amphibians and reptiles being discovered from limestone areas (e.g. see discussions in Milto et al, 2013 ; Grismer et al, 2014 ; Grismer & Grismer, 2017 ; Grismer et al, 2016a , 2016b , 2017 , 2018 ; Nazarov et al, 2014 , 2018 ; Connette et al, 2017 ; Suwannapoom et al, 2018 and references therein). Ironically, though acting as major biodiversity hotspots, limestone karsts are critically endangered due to unregulated quarrying mostly for cement manufacturing, which is the primary threat to the survival of karst-associated species ( Grismer et al, 2018 ); their continued exploitation for limestone cannot be stopped ( Clements et al, 2006 ).…”

中南半岛发现姬蛙科一新属及三个新种（两栖纲：无尾目）

“…We amplified mtDNA fragments, covering partial sequences of the 12S rRNA and 16S rRNA mtDNA genes and complete sequence of the tRNA mtDNA gene to obtain a 2 591-bp long continuous fragment of mtDNA. These mtDNA markers have been used for comprehensive phylogenetic studies on Microhylidae frogs ( De Sá et al, 2012 ; Matsui et al, 2011 ; Peloso et al, 2016 ; Pyron & Wiens, 2011 ; Van Der Meijden et al, 2007 ; and references therein), including molecular taxonomic research on the subfamily Asterophryinae ( Blackburn et al, 2013 ; Frost et al, 2006 ; Günther et al, 2010 ; Köhler & Günther, 2008 ; Kurabayashi et al, 2011 ; Oliver et al, 2013 ; Rittmeyer et al, 2012 ; Suwannapoom et al, 2018 ). PCR was performed in 20 L reactions using 50 ng of genomic DNA, 10 nmol of each primer, 15 nmol of each dNTP, 50 nmol of additional MgCl 2 , Taq PCR buffer (10 mmol/L of Tris-HCl, pH 8.3, 50 mmol/L of KCl, 1.1 mmol/L of MgCl 2 and 0.01% gelatin), and 1 U of Taq DNA polymerase.…”

“…PCR was performed in 20 L reactions using 50 ng of genomic DNA, 10 nmol of each primer, 15 nmol of each dNTP, 50 nmol of additional MgCl 2 , Taq PCR buffer (10 mmol/L of Tris-HCl, pH 8.3, 50 mmol/L of KCl, 1.1 mmol/L of MgCl 2 and 0.01% gelatin), and 1 U of Taq DNA polymerase. The PCR conditions as well as primers used for PCR procedures and sequencing followed Suwannapoom et al ( 2018 ).…”

“…In their work, Kurabayashi et al ( 2011:9 ) predicted, that the “biogeographic findings on Gastrophrynoides imply the possible occurrence of further microhylid taxa with unexpected evolutionary backgrounds and give a basis for future paleontological and biogeographic studies of Asian anurans”. Our more recent work ( Suwannapoom et al, 2018 ) reported on the unexpected discovery of Siamophryne — a striking troglophilous microhylid frog found in a limestone cave in Tenasserim (southern Thailand) — with phylogenetic analyses placing it as a sister lineage of Gastrophrynoides , further suggesting that mainland Southeast Asia likely served as a cradle of initial divergence and radiation of asterophryine frogs.…”