DIVERSITY & ENDEMISM
Biogeographically, the Himalayan Mountain Range straddles a transition zone between the Palearctic and Indo-Malayan realms. Species from both realms are represented in the hotspot. In addition, geological, climatic and altitudinal variations in the hotspot, as well as topographic complexity, contribute to the biological diversity of the mountains along their east-west and north-south axes.
Of the estimated 10,000 species of plants in the Himalaya hotspot, about 3,160 are endemic, as are 71 genera. Furthermore, five plant families are endemic to the region, the Tetracentraceae, Hamamelidaceae, Circaesteraceae, Butomaceae and Stachyuraceae. The largest family of flowering plants in the hotspot is the Orchidacea, with 750 species, and a large number of orchids, many representing rather young endemic species, have recently been reported from the hotspot, indicating that further exploration will probably reveal a much higher degree of plant endemism. The Eastern Himalaya is also a center of diversity for several widely distributed plant taxa, such as Rhododendron, Primula, and Pedicularis.
In the Himalaya Hotspot, a zone of permanent rock and ice begins at about 5,500-6,000 meters; in spite of these harsh conditions, there are records of vascular plants occurring at some of the highest elevations on Earth. Cushion plants have been recorded at more than 6,100 meters, while a high-altitude scree plant in the mustard family, Ermania himalayensis, was found at 6,300 meters on the slopes of Mt. Kamet in the northwestern Himalayas.
Nearly 980 birds have been recorded in the hotspot, but only 15 are endemic. The Critically Endangered Himalayan quail (Ophrysia superciliosa) represents an endemic genus in the region, although it has not been recorded with certainty since 1876, despite reports of possible sightings around Nainital in 2003.
BirdLife International has identified four Endemic Bird Areas that overlap partially or fully with the Himalaya hotspot. The Western Himalaya EBA has 11 species restricted to it, including the Himalayan quail as well as the cheer pheasant (Catreus wallichii, VU) and the western tragopan (Tragopan melanocephalus, VU). The Eastern Himalaya EBA, which also overlaps with part of the Indo-Burma Hotspot, has nearly 20 endemic species, including four that are fully endemic to the Himalayas: the chestnut-breasted partridge (Arborophila mandellii, VU) and rusty-throated wren babbler (Spelaeornis badeigularis, VU), plus the white-throated tit (Aegithalos niveogularis) and orange bullfinch (Pyrrhula aurantiaca).
Some of Asia's largest birds live in this hotspot, and many are threatened by human activities. For example, some of the region's vultures (Gyps spp.) have undergone dramatic declines after feeding on the carcasses of cattle that have been treated with the anti-inflammatory drug diclofenac. Of other birds present in the hotspot, the greater and lesser adjutants (Leptoptilos spp.) in the foothill grasslands and broadleaf forests, as well as the hornbills in the broadleaf forests, are threatened by loss of nesting trees and lack of food sources.
Other avian flagships include the white-winged duck (Cairina scutulata, EN), the endemic white-bellied heron (Ardea insignis, EN), and the Bengal florican (Houbaropsis bengalensis, EN).
About 300 mammal species have been recorded in the Himalayas, including a dozen that are endemic to the hotspot. Among the endemic species are the golden langur (Trachypithecus geeiHemitragus jemlahicus, VU) and the pygmy hog (Sus salvanius, CR), which has its stronghold in the Manas National Park. The only endemic genus in the hotspot is the Namadapha flying squirrel (Biswamoyopterus biswasi, CR), described only from a single specimen from Namdapha National Park.
The mammalian fauna in the lowlands is typically Indo-Malayan, consisting of langurs (Semnopithecus spp.), Asiatic wild dogs (Cuon alpinus, VU), sloth bears (Melursus ursinus, VU), gaurs (Bos gaurus, VU), and several species of deer, such as muntjac (Muntiacus muntjak) and sambar (Cervus unicolor). In the mountains, the fauna transitions into Palearctic species, consisting of snow leopard (Uncia uncia, EN), black bear (Ursus thibetanus, VU), and a diverse ungulate assemblage that includes blue sheep (Pseudois nayaur), takin (Budorcas taxicolor, VU), and argali ( Ovis ammon, VU).
The alluvial grasslands support some of the highest densities of tigers (Panthera tigris, EN) in the world, while the Brahmaputra and Ganges rivers that flow along the foothills also support globally important populations of the freshwater Gangetic dolphin ( Platanista gangetica). Some of the world's last remaining populations of wild water buffalo ( Bubalus bubalis, EN) and swamp deer (Cervus duvaucelii, VU) are restricted to protected areas in southern Nepal and northeastern India.
Alhough there has been little systematic study of reptiles and amphibians in the Himalaya hotspot, at least 175 reptiles have been documented, of which nearly 50 are endemic. There is just one endemic genus, represented by a single species, the lizard Mictopholis austeniana, known only from the holotype. Other genera are well represented, and have many endemic species. These include Oligodon, Cyrtodactylus, and Japalura.
Among amphibians, there are 105 species known to occur in the hotspot, more than 40 of which are endemic. Most of these are frogs and toads, although there are also two species of caecilians, one of which, (Ichthyophis sikkimensis, is endemic and occurs in northern India (in the States of Sikkim and West Bengal) and extreme eastern Nepal (in Dabugaun in the Ilam District) at elevations of 1,000 to 1,550 meters.
Fish species from three major drainage systems, the Indus, Ganges, and Brahmaputra, inhabit the Himalaya hotspot, although the ranges of many species only just reach into the cold, high-altitude waterways of this region. As a result, only 30 of nearly 270 species are endemic.
The three most diverse of the 30 different families represented here are minnows and carps (Cyprinidae; 93 species and 11 endemics), river loaches (Balitoridae; 47 species and 14 endemics), and sisorid catfishes (Sisoridae; 34 species and four endemics). The genus Schizothorax is represented by at least six endemic species in the high mountain lakes and streams, while two other genera of these snowtrout, the genus Ptychobarbus and the Ladakh snowtrout (Gymnocypris biswasi) — a monotypic genus now thought to be extinct — are also unique to the Himalaya Hotspot.