As one of the 17 megadiverse countries of the world and with four biodiversity hotspots represented in its borders, India is home to an impressive diversity of life forms. However, much work remains to document and catalogue the species of India and their geographic distributions, especially for diverse invertebrate groups. In the present study, a comprehensive and critical list of Indian ant species is provided with up-to-date state-wise distribution. A total of 828 valid species and subspecies names belonging to 100 genera are listed from India. Potential erroneous data, misidentifications and dubious distributional records that may exist in the literature are also identified. The present exhaustive listing of Indian ants will provide a holistic view about diversity and distribution and will also help to identify major undersampled areas where future sampling and taxonomic efforts should be directed.

Checklist, Indian Ants, Formicidae

The Indian subcontinent is well known for its high biodiversity, varied environments and habitats, and interesting geological history. However, much work remains to document and catalogue the species of India and their geographic distributions, especially for diverse invertebrate groups. The country, with a total land area of over 3.2 million km², is positioned on the Indian Plate (the northern portion of Indo-Australian plate) which separated from Gondwanaland during the late Cretaceous, then collided with Eurasia in the Cenozoic (Briggs 2003, Lomolino et al. 2010), although the precise age of this event is still debated (Aitchison et al. 2007). The collision led to the formation of Tibetan Plateau and the Himalaya. The Indian Plate has acted as a vessel carrying fauna and flora from Africa and Madagascar to Eurasia (Briggs 2003). This varied geological history has led to the emergence of a wide diversity of flora and fauna in India, which comprises Malayan, Afrotropical, Mediterranean, central Asian and eastern Palearctic elements.

Most of the country’s land can be assigned to one of two ecozones, the Palaearctic and Indo-Malayan, and 13 terrestrial ecoregions (Olson et al. 2001). The Himalayan system, part of the Palaearctic ecozone, stretches over 3000 kilometers in length, from Myanmar to east of Afghanistan (between longitudes 70E to 100E and latitudes 25N to 40N) and from 80 kilometers to 300 kilometers in width (Bharti 2008). The Himalayas, which form the northern boundary of the country, span across ten states (Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, Meghalaya, Tripura, Manipur, Mizoram, Nagaland, Arunachal Pradesh and a little part of Assam and West Bengal). The mountain system extends from east of Brahmaputra to the bend of Indus in the west, but the Himalayan system stretches further from Myanmar to Afghanistan. Kunlun represents the northern extreme of the Himalayan range, followed by the Tibetan plateau. The mountain system meets with high ranges of Central Asia (Hindu Kush, Trans Karakoram, Tian Shan, Kunlun, Trans Alai) forming the Pamir Knot, and Tibet lies to the north-east. The Western Ghats are part of the Western Ghats-Sri Lanka global hotspot, running roughly in a North-south direction for about 1500 kilometres parallel to the coast bordering the Arabian Sea.

Approximately 21% of the country’s landmass is covered by forests (tree canopy density >10%), of which 12% comprises moderately or very dense forests (tree canopy density >40%) (CBD 2014). These include tropical rainforests of the Andaman Islands, the Western Ghats, and Northeast India; coniferous forests of Himalaya; deciduous Sal (Shorea robusta) forest of Eastern India; the dry deciduous Teak (various species of Tectona) forest of Central and Southern India; and the Babul (Acacia) dominated thorn forest of the Central Deccan and Western Gangetic plain (Tritsch 2001). According to the latest estimates (CBD 2014), the country accounts for 7–8% of the total plant and animal species globally recorded, including over 45,000 species of plants and 92,873 species of animals. This included 423 mammalian species (7.81% of Indian total), 1,233 avian species (13.66%), 526 reptilian species (5.7%), 342 amphibian species (5.05%), 3,022 fish species (9.41%) and 63,423 of insects species (6.22%). Out of these, about 4,045 species of flowering plant (angiosperms), 47 species of mammals, 53 species of birds, 156 species of reptiles and 168 species of amphibians are endemic to India (CBD 2014). Most of the endemic taxa listed above are localised in one of the four biodiversity hotspots recognised in India; Himalaya, Indo-Burma, the Western Ghats - Sri Lanka and Sundaland (Nicobar Islands) (Myers et al. 2000 and CBD 2014).

Current data about the diversity and distribution of Indian ants is provided in this work. Ants constitute an important fraction of the animal biomass in terrestrial ecosystems and respond to stress on a much finer scale compared to vertebrates (Hölldobler and Wilson 1990; Andersen 1997). They are widely used to assess landscape disturbance and species diversity (Paknia and Pfeiffer 2011). They perform major ecological functions (predators, scavengers, soil turners, nutrient cyclers, pollinators) and are also responsible for dispersal of numerous plant species (Lach et al. 2010, Del Toro et al. 2012, Guénard 2013). Furthermore, ants mark their presence at almost all levels of terrestrial food webs (Pfeiffer et al. 2013). In this context, knowledge about their diversity and distribution may add to our understanding of their ecological functions, biogeographic patterns and global affinities.

Jerdon (1851, 1854) catalogued the ants of Southern India. Later, Forel (1900a,b, 1901) extended the list by adding 267 new species from the region. Comprehensive documentation of Indian ants was carried by Bingham (1903), who included all the previous works. Later, further contributions were made by various myrmecologists including Forel, Donisthorpe, Emery, Santschi, Mukerjee, Brown, Bolton in terms of descriptions of new taxa (Appendix 1). However, the first ever checklist which cited Indian ants was published by Chapman and Capco (1951; Appendix 1) in their revision of Asian ants. Later efforts to combine knowledge on Indian ants were performed by Guénard and collaborators (Guénard et al. 2010; 2012) in the context of global generic richness and distribution in Asia. In recent years, Bharti and co-workers significantly increased our understanding of ant diversity with both new species descriptions and new distributional records (Appendix 1). This led Bharti (2011) to compile the first modern species checklist inclusive of all earlier records for 652 valid species and subspecies from India and include all the ant records from Himalaya irrespective of its political division. Despite all these efforts, our knowledge about the diversity and distribution of Indian ants remains incomplete and fragmentary, especially on finer geographic scales.

In the present study we provide a comprehensive and critical list of Indian ants with current known state-wise distribution. Our aim is to consolidate previous data, to identify potential erroneous data, misidentifications, dubious distributional records, and more generally to provide a holistic view about the diversity and distribution of Indian ants. This list should also help identify major undersampled areas where future sampling and taxonomic efforts should be directed.

Species lists were compiled for 28 Indian states and two union territories (Andaman and Nicobar Islands and Delhi). Data from Union territories of Chandigarh were merged with Punjab, Dadra and Nagar Haveli with Maharashtra, Daman and Diu with Goa, Lakshadweep with Kerala, and data for the state of Telangana were merged with Andhra Pradesh. These lists have been generated based on the literature review of published material, physical examination of material lying in Natural History Museum, London; Indian depositories; personal collection of the first author and websites (cited in the reference section). Additionally, the outcome of recent surveys in approximately the last 15 years in the various regions of India have also significantly enriched the data and have added to the much needed distributional data of various species. Morphospecies have not been included in the list and species name validity, authority and spelling conform to Bolton’s (2015) Synopsis of the Formicidae and Catalogue of Ants of the World.

From India, distributional data for 828 species and subspecies is listed, representing 100 genera grouped in 10 subfamilies. In terms of species richness, the subfamily Myrmicinae is the most speciose (354 species, 42.7%), followed by Formicinae (241 species, 29.1%) Ponerinae (111 species, 13.4%), Dorylinae (55 species, 6.6%) and Dolichoderinae (30 species, 3.6%), while the rest of the smaller subfamilies together constitute 4.2% (Pseudomyrmecinae 11 species, Amblyoponinae 10 species, Proceratiinae 6 species, Ectatomminae 5 species and Leptanillinae 4 species). The trend for generic richness is almost the same except for the subfamily Ponerinae which represents a larger percentage of generic richness than Formicinae (Myrmicinae 37.4%, Ponerinae 20.2% and Formicinae 18.2%).

Undersampling and future directions

With 828 species recorded, India represents one of the richest countries in the Indo-Malayan region. India remains less diverse than China with over 950 species recorded (Guénard and Dunn 2012; Liu et al. 2015), but similar to the island of Borneo (Pfeiffer et al. 2011, http://antmaps.org) and more diverse than the Philippines (General and Alpert 2012, http://antmaps.org). However, considering the high number of species recently described from India by Bharti & co-workers (Appendix 1) and the lack of knowledge for a large part of India (Figure 2), there is little doubt the number of ant species reported from India should keep increasing in the forseeable future.

Figure 1. 

List and geographic position of Indian states considered in this study

Figure 2. 

Generic (A) and species (B) richness based on nominal species for the different states of India.

We present, for the first time, patterns of species richness for the different Indian states, and thereby provide a more detailed biogeographic picture of ant richness. Above all, these results reveal large areas lacking surveys and/or taxonomic resolution on the local myrmecofauna (Figure 2A, B). Our results indicate that no less than seventeen of the thirty administrative regions studied (57%) have fewer than 100 species recorded. In comparison, this roughly corresponds to the species richness observed in countries located in cooler-temperate regions like Poland (Czechowski et al. 2012) or North Korea (Radchenko 2005). Considering the geographic position of Indian states and their climatic ranges (Attri and Tyagi 2010), with most of these regions located in humid subtropical, wet and dry tropical or semi-arid climates, the faunal richness for these regions should be much higher than our current data indicate. For example, the small, Himalayan state of Sikkim (278 species) has higher recorded richness than the tropical moist region of Kerala (259 species). Similarly, regions of the northeastern part of India bordering Myanmar have highly diverse tropical moist forest ecosystems, but only have sparse records for ants.

These gaps in our current knowledge underscores the need for vigorous sampling and identification programs to target specific regions of India. Moreover, due to this incomplete knowledge, the true richness of the Indian ant fauna cannot be assessed with high confidence at this time. However, in light of the undersampling of most regions of the country, we expect the true richness to be greater than 1000 species.

As some of the states/regions are clearly undersampled, future explorations will reveal more species diversity of ants from India. Similarly, upcoming taxonomic revisions will redefine species boundaries, species distributions and affinities with adjoining biogeographic regions. Consequently, the data presented here marks a waypoint in the effort towards elucidating the regional diversity and distribution of Indian ants. In light of the ecological importance of ants in most terrestrial ecosystems, the relatively poor available knowledge of ants in most Indian states, and the high level of endemism of Indian ants, we encourage urgent, large-scale, and sustained efforts to monitor, characterize, and conserve the Indian myrmecofauna.