Recent Progress in Taxonomic Studies, Biogeographic Analysis, and Revised Checklist of Amphibians in Indochina

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The Indochinese Peninsula is recognized as one of the key global biodiversity hotspots. The amphibian fauna of Indochina (including Vietnam, Laos, Cambodia and Thailand) is one of the richest in the world. About 60% of the known species were described within the last 20 years. We review the literature and our data to assess all recent discoveries and taxonomic changes and compile the first annotated checklist of the amphibian fauna of Indochina since the middle of the 20th century, including updated faunal lists for Vietnam and Thailand. Amphibian checklists for Laos and Cambodia are published for the first time. For each species we provide the following information: scientific name; recommended common name in English; information on type specimens; type locality; data on its distribution within Indochina and beyond; IUCN conservation status; taxonomic comment and the most important references. We review the distribution of each species across the 23 biogeographic subregions of Indochina, estimate the similarity among the regional faunas and evaluate their species richness and endemism. In total we record 423 amphibian species belonging to three orders, 11 families and 71 genera; 199 species (47%) are endemic to Indochina. Comprising 270 known species, the amphibian fauna of Vietnam is the richest (98 endemics, 36.3%), followed by Thailand with 194 species (29 endemics, 14.9%), Laos with 121 species (13 endemics, 10.7%), and Cambodia with 72 species (6 endemics, 8.3%). A cluster analysis of faunal similarity between the subregions shows two major assemblages, divided by the Isthmus of Kra. Within the northern mainland portion of Indochina three clusters can be distinguished: (1) northeastern and northwestern uplands of Vietnam and northern Laos; (2) Northern, Central, and Southern Annamites, the Bolaven Plateau, and central-south Vietnam lowlands; (3) western Indochinese subregions. We identify the Northeast and Northwest Uplands of Vietnam, the Northern, Central and Southern Annamites, the Cardamom Mountains, the mountains of Northeast Thailand, Northern Tenasserim and southern Peninsular Thailand as nine major centers of diversity and endemism of Indochinese amphibians. The analysis of amphibian distribution patterns across Indochina suggests the presence of 14 chorotypes grouped in five major range types. Our results underline the role of Indochina as a key area for amphibian diversity and conservation. Among 423 species of Indochinese amphibians, 152 species (35.9%) were considered as data deficient (DD) or were not evaluated (NE) according to the IUCN Red List criteria; while 76 species (18.0%) were considered vulnerable (VU), endangered (EN) or critically endangered (CR), 20 species (4.7%) were considered to be near threatened (NT), and 175 species (41.4%) to be of the least concern (LC). Our study thus has implications for further conservation efforts on regional and global levels, as well as for understanding the biogeographic patterns of amphibian richness and endemism in Asia.