Tenasserim faunal region

Tenasserim faunal region
Name	Tenasserim faunal region
Country	Myanmar, Thailand
Area km2	200000
Bioregion	Indomalayan realm
Highest point	Doi Inthanon

Tenasserim faunal region is a biogeographic subdivision of the Indomalayan realm spanning the Isthmus of Kra southward through the Tenasserim Hills along the borderlands of Myanmar and Thailand, extending toward the Malay Peninsula. The region links montane systems such as Doi Suthep and Khao Luang with lowland complexes including Titiwangsa Mountains fragments and coastal zones adjacent to the Andaman Sea, forming a corridor for species exchange between Southeast Asia and Peninsular Malaysia.

Geography and boundaries

The region occupies a narrow, elongated tract from the southern margins of Myanmar near Myeik and Dawei through the Tenasserim Range bordering Ranong and Phang Nga provinces before tapering toward Songkhla and the Isthmus of Kra. Boundaries are defined against adjacent provinces like the Irrawaddy Basin and the Chao Phraya Basin, and abut the Sunda Shelf-influenced zones of the Malay Peninsula. Major river systems such as the Salween River, Pattani River, and smaller coastal estuaries create physiographic demarcations, while protected areas like Khao Sok National Park, Kaeng Krachan National Park, and Tanintharyi Nature Reserve sit within or adjacent to the region.

Geology and climate

The orogeny of the Tenasserim Hills reflects accretionary processes related to the Indian Plate–Sunda Plate interaction and preserves metamorphic, ophiolitic, and sedimentary sequences comparable to those seen in the Tenasserim–Titiwangsa belt and parts of the Malay Peninsula. Soils range from lateritic profiles on uplands to alluvial deposits along coastal plains near Mergui Archipelago islands. Climatically, the region is dominated by the Southwest Monsoon and Northeast Monsoon regimes, producing a pronounced wet season and a drier intermonsoonal period; rainfall gradients mirror elevation and maritime exposure seen at sites like Phang Nga Bay and Ranong Hot Springs.

Flora and vegetation types

Vegetation gradients encompass evergreen lowland dipterocarp forests similar to those recorded in Kaeng Krachan and Khao Sok, transitioning into montane oak–laurel assemblages on peaks akin to Doi Inthanon and Khao Luang. Mangrove stands occupy estuaries adjoining Andaman Sea inlets and are comparable to those catalogued near Mergui Archipelago. Floristic elements show affinity with genera documented in Peninsular Malaysia, Sumatra, and Borneo, including representatives of Dipterocarpaceae, Lauraceae, Myrtaceae, and specialized epiphytes such as those recorded in Doi Suthep–Pui National Park.

Faunal assemblages and endemism

Faunal communities include terrestrial and marine taxa with taxonomic overlap with the Indochinese and Sundaland biotas, incorporating iconic mammals, birds, reptiles, amphibians, and invertebrates found in Kaeng Krachan and Khao Sok. Mammalian assemblages document species analogous to records from Tanintharyi and Peninsular Malaysia, including large carnivores and ungulates whose ranges intersect conservation landscapes like Khao Nor Chuchi. Avian diversity reflects passage and residency patterns similar to Pak Thale and Hat Yai, while herpetofauna displays high beta diversity with endemics comparable to taxa described from Nakhon Si Thammarat and Phuket. Freshwater fish and crustaceans mirror lineages recorded in the Salween River and coastal archipelagos such as Mergui Archipelago. Endemism is concentrated in isolated montane outcrops and karst systems resembling the endemic hotspots of Langkawi and Khao Sam Roi Yot.

Biogeographic history and faunal connections

The region functions as a biogeographic corridor and filter between continental Southeast Asia and Sundaic islands. Pleistocene sea-level fluctuations on the Sunda Shelf and repeated connections across the Isthmus of Kra facilitated dispersal events mirrored in phylogeographic patterns documented for taxa across Sumatra, Peninsular Malaysia, and Borneo. Tectonic uplift associated with the Indian Plate–Sunda Plate boundary and climatic oscillations tied to Last Glacial Maximum cycles drove range fragmentation and allopatric speciation similar to processes inferred in studies of Doi Inthanon endemics and Tenasserim-adjacent populations. Paleobiogeographic affinities link to faunal assemblages recorded in historic collections by expeditions referencing British Burma and naturalists associated with institutions such as the British Museum (Natural History) and Smithsonian Institution.

Conservation status and threats

Conservation in the region faces pressures from deforestation for plantations similar to land-use changes documented in Songkhla Province and Perlis, infrastructure expansion including road corridors and hydropower projects observed near Salween River tributaries, and extractive activities analogous to operations in Tanintharyi oil palm concessions. Protected area networks such as Kaeng Krachan and Khao Sok provide refugia but are challenged by illegal wildlife trade linked to trafficking routes through Mergui Archipelago and cross-border markets in urban centers like Bangkok and Yangon. Climate change, sea-level rise affecting Andaman Sea coasts, and fragmentation mirror threats facing adjacent ecoregions and complicate transboundary conservation initiatives involving organizations like WWF and governmental agencies in Myanmar and Thailand. Urgent priorities include landscape-scale connectivity, community-based management modeled on successes in Karen State and participatory conservation initiatives documented by Fauna & Flora International.

Category:Biogeography