India is one of the world’s most biodiverse regions. Within its total land area of about 3,287,263 square kilometers, it harbors a variety of eco-zones ranging from deserts to high mountains and tropical to temperate forests. The country is situated on the Indian Plate, a tectonic plate which separated from Gondwanaland during the late Cretaceous, then collided with Eurasia in the Coenozoic. The collision led to the formation of Tibetan Plateau and the Himalayas. This varied geological history has led to the emergence of a wide diversity of flora and fauna in India.
The ant fauna is representative of this diversity, and includes 12 of the 22 known subfamilies (Aenictinae, Amblyoponinae, Cerapachyinae, Dolichoderinae, Dorylinae, Ectatomminae, Formicinae, Leptanillinae, Myrmicinae, Ponerinae, Proceratiinae, Pseudomyrmecinae). The current species list includes approximately 660 species from 87 genera and will continue to increase in number as researchers begin to systematically explore the diverse habitats of ants across the region. Ants in India occupy a variety of habitats such as leaf litter, trees, soil, and dead logs, while tramp speciesprefer human-modified habitats.
Myrmicinae forms the bulk of Indian ant diversity (45%) with Pheidole and Crematogaster having the most species. The subfamily Formicinae is the second largest ant group (25% of species), with Camponotus and Polyrhachis constituting the majority of the diversity. The subfamily Ponerinae contributes about 14% of species of which Leptogenys the most diverse.
Five Indian ant species are on the IUCN red list. The majority of catalogued species are of Indo-Malayan origin. Tramp/invasive ant species such as Paratrechina longicornis longicornis, Tapinoma melanocephalum melanocephalum, Anoplolepis gracilipes, and pest species such as Monomorium indicum and Monomorium pharaonis have already invaded Indian ecosytems, with Solenopsis invicta waiting in the wings (Bharti, 2009 in press).
The ecosystems of two important eco-regions, the Himalayas and Western Ghats, are under serious threat. Both areas are also listed as biodiversity hot spots, and their ants merit special mention.
The Himalayan system, which is more than 3,000 kilometers long, harbors about 202 species of ants, with 45% being endemic to the region (Bharti, 2008). Himalayan ecology is temperature dependent and altitudinal gradients have a remarkable effect on ant species composition and abundance (Bharti, 2009). Genera such as Myrmica, Aphaenogaster, Lasius, Temnothorax and Formica dominate the higher Himalayan ranges and nest under stones but do not penetrate more temperate, lower elevation areas.
By contrast, the Siwalik Range, the southernmost east-west range of the Himalayas, has a more moderate elevation and harbors more generalist species. The Siwalik Range is also more prone to human habitat disruption. Ant species are being monitored there to indicate the degree of local disturbance.
The Western Ghats mountains stretch along the western edge of India. They cover an area of 60,000 km2 with an average elevation of about 1,200 meters. The climate is humid, tropical in lower elevations and temperate in higher ranges. Its tropical and subtropical forests are marked by agricultural fields and grasslands. This mosaic environment provides excellent habitats for ants. Arboreal ants such as Oecophylla, Camponotus, Polyrhachis and Crematogaster can be found in the tree canopy, while Aenictus, Cerapachys, and Strumigenys find sustenance in rotten logs, leaf litter and soil. Interestingly, the forest floor is dominated by Harpegnathos, Diacamma, Platythyrea and a few other ponerines.
Indian ants display a remarkable range of diversity with many more taxa still to be discovered. We welcome the contributions of others in developing this comprehensive list of Indian ants.