An updated checklist of Nepalese ants (Hymenoptera, Formicidae)

Abstract The location of Nepal in the Central Himalaya promotes high habitat and species diversity. Ant diversity is likely high, but there have been few studies of the diversity and distribution of ants in Nepal. Here we present an updated checklist list of Nepalese ants that includes 128 named species in 48 genera and eight subfamilies. Among these species, 21 species have a type locality from Nepal, nine species are endemic to Nepal, and three are introduced species. We add six new ant records for Nepal, namely Harpegnathos venator, Monomorium pharaonis, Nylanderia bourbonica, Odontoponera denticulata, Polyrhachis tyrannica and Pseudoneoponera bispinosa. The checklist presents distribution records for Nepalese ant species and provides comparisons with the neighboring countries of China and India.


Introduction
Ants (family Formicidae) are one of the most successful groups of organisms on the planet (Hölldobler and Wilson 1990) and together with termites, have been found to make up 30% of animal biomass in the Amazon rain forest (Fittkau and Klinge 1973). Ants are present in almost all terrestrial ecosystems, with the peak of their diversity found within the tropical regions (Guénard 2013). Estimate of global ant species rich-ness exceeds 20,000 species (Hölldobler and Wilson 1990). Seventeen valid subfamilies, 337 genera, and over 13,837 species of ants have been described (Bolton 2020). Over 87% of all described ant species belong to four main subfamilies: Myrmicinae, Formicinae, Ponerinae, and Dolichoderinae (Guénard 2013). Global Ant Biodiversity Informatics (GABI) is the first comprehensive global database with ant species records in available publications and existing databases (Guénard et al. 2017).
Nepal is a Himalayan country located in the Oriental region at the junction of the Palaearctic and Palaeotropic regions. Nepal covers an area of 147,516 km 2 and lies in the center of the Himalayas between latitudes 26°28.986'N to 29°50.4726'N and longitudes 80°19.9998'E to 88°5.6616'E. Its unique geographical and ecological diversity promote a high diversity of flora and fauna, including of ants. However, the study of ants in Nepal is still in its infancy. The diversity and distribution of ants in Nepal is little known and there are few published records of ants of Nepal.
Early compilations of the ants of the Indian region by Bingham (1903) and of Asia by Chapman and Capco (1951) did not include ants from Nepal. The first reports of Nepalese ants were Aphaenogaster pachei and Myrmica pachei by Forel (1906). The next record of Nepalese ants appeared in Menozzi (1939). Collingwood (1970) published the first list of 34 species of ants of Nepal from the collections of the 1954 British Museum expedition to east Nepal and from Professor H Janetshek's 1961 expedition to the Khumbu Himal region. Summaries of the insects of Nepal by Thapa (2000Thapa ( , 2015 listed 44 species (24 genera) of ants and 52 species (44 named species; 29 genera) of ants, respectively. The number of Nepalese ant species reported in online ant databases ranges from 57 named species (AntWeb 2020) to 86 species/subspecies (AntWiki 2020) to 141 species (antmaps.org 2020) but some of the records need verification of their occurrences in Nepal.
Thus, the information available on the diversity and distribution of Nepalese ants is scattered and incomplete. As a first step towards filling information gaps, this paper presents a thorough review of publications on the ants of Nepal to provide an up-todate checklist of Nepalese ants. We also add additional species records and distribution information from collections done by the first author. This paper further compares the occurrence of the Nepalese ants in the neighboring countries of China and India. This checklist provides a baseline for Nepalese ant diversity and will hopefully stimulate additional research on the myrmecofauna of Nepal.

Materials and methods
The species list of the ants of Nepal has been synthesized from a literature review of articles, books and reports. Information was also extracted from the online ant databases, AntWeb (2020) and AntWiki (2020) and species distribution information from antmaps.org (Janicki et al. 2016;Guénard et al. 2017). Species described as morphospecies or unidentified species are not included in this checklist. The data presented here are based mainly on existing literature and are thus dependent on the quality of the identification made by the authors at the time the record was published. New records and additional distribution localities of Nepalese ants were provided from the first author's collection, deposited at Central Department Zoology Museum of Tribhuvan University, Nepal, CDZMTU. Taxonomic changes made to some of the Nepalese ant taxa are also incorporated. The valid name, spelling and authority of ant species were updated from Bolton (2020).
The subfamilies, genera within a subfamily, and species within a genus are arranged alphabetically. For each genus, type species and type locality are also provided. The species list provides the distribution range within Nepal including district, specific locality, altitude, collectors' names, and depositories of ant specimens based upon the availability of data. Separate lists of the ant species first described from Nepal, endemic species of Nepal, and introduced species are also presented. A comparison of the occurrence of Nepalese ants in the neighboring countries of China and India is also included, which could aid in assessing the patterns of diversity and composition of Nepalese ants. Previously reported species if not substantiated by specimens or literature records, are marked as dubious/unverified. They have been excluded from the main species list and presented in a separate list.

Results and discussion
The checklist of the ants of Nepal includes 128 valid species. These ant species represent ca. 0.9% of the global ant diversity (Bolton 2020). The list includes nine ant species endemic to Nepal and three introduced species. Twenty-one ant species were first described from Nepalese specimens. A comparison of the Nepalese ant species to those of the surrounding countries of China and India is also presented.

Species and generic diversity within subfamily
The presented checklist is comprised of 128 named ant species belonging to 48 genera and eight subfamilies (see checklist below). The eight recorded subfamilies are Amblyoponinae, Dolichoderinae, Dorylinae, Formicinae, Leptanillinae, Myrmicinae, Ponerinae, and Pseudomyrmecinae. The ant species and genus level richness for each subfamily is given in Table 1.
This paper adds 84 named ant species to the list of Nepalese ants since the publication of Thapa's 2015 "Insect diversity in Nepal" which listed 44 named ant species based upon bibliographic review. Further, this paper adds 79 named ant species to the AntWeb (2020) list and 46 named species to the AntWiki (2020) list. In light of the ant species richness found in neighboring countries (e.g., China: Guénard and Dunn 2012;India: Bharti et al. 2016a) and the ecological diversity of Nepal, many more than the 128 ant species on this checklist can be expected from Nepal. The majority of early ant collections on which the list is mainly based were done by direct hand collecting, which was not extensive. The checklist records show that the entire country is under sampled and that little sampling effort has been made in the western and southern regions in particular. To overcome this sampling bias and to establish a more thorough ant species list, we recommend that future investigations of ant diversity following standard ant sampling techniques (see Agosti and Alonso 2000) in all parts of the country. A more intensive and systematic collection of Nepalese ants would certainly add new species and new distribution records.

New ant records for Nepal
Six ant species, namely Harpegnathos venator, Monomorium pharaonis, Nylanderia bourbonica, Odontoponera denticulata, Polyrhachis tyrannica and Pseudoneoponera bispinosa are new records for Nepal identified from the first author's collection. The ant genus Harpegnathos is recorded for the first time for Nepal.

Endemic ants of Nepal and the species described from Nepalese specimens
Of the 128 ant species recorded from Nepal, 21 species were described from Nepalese specimens and nine species are considered endemic to Nepal (Table 2). No ant genera are known to be endemic to Nepal. However, voucher specimens from previous records from Nepal were not found to be deposited in the country. Three ant species, namely Paratrechina longicornis, Trichomyrmex destructor and Monomorium pharaonis are globally distributed ant species that have been introduced into Nepal.  (Forel, 1906) Strumigenys exilirhina Bolton, 2000Mayriella transfuga Baroni Urbani, 1977 Strumigenys hemisobek (Bolton, 2000) *Meranoplus nepalensis Schödl, 1998 *Strumigenys hindu De Andrade, 2007 Myrmica alperti Elmes & Radchenko, 2009 Strumigenys nepalensis De Andrade, 1994 *Myrmica boltoni Radchenko & Elmes, 1998 Strumigenys podarge (Bolton, 2000) Myrmica brancuccii Radchenko, Elmes & Collingwood, 1999 Tetramorium difficile Bolton, 1977 *Myrmica martensi Radchenko & Elmes, 1998 *Emeryopone franzi (Baroni Urbani, 1975) Myrmica pachei Forel, 1906 China. Fifty-nine species are found in all three countries and 26 species are unique to Nepal. Almost half of the genera recorded from India (100) and China (103) are also recorded from Nepal (48). In terms of named and recorded species, Nepal harbors approximately 15% of the species from India and nearly 14% of the species from China. Interestingly, 47 ant species recorded from Nepal have India as the type locality while only six species have China as the type locality.

Conclusions
An updated checklist of the ants of Nepal contains 128 valid ant species belonging to 48 genera and eight subfamilies. Six ant species (Harpegnathos venator, Monomorium pharaonis, Nylanderia bourbonica, Odontoponera denticulata, Polyrhachis tyrannica and Pseudoneoponera bispinosa) are new records for Nepal. The ant genus Harpegnathos is recorded for the first time for Nepal. The most speciose subfamily and genus in Nepal are Myrmicinae and Myrmica respectively. Overall, 21 species were first described from Nepalese specimens, nine species are endemic to Nepal, and three ant species are introduced species. No ant genera are known to be endemic to Nepal. Nepal shares over half of the listed ant species with its neighboring countries.
Despite an extensive literature review, the checklist remains incomplete because it is based on limited sampling efforts and on inadequate taxonomic knowledge of the ants of Nepal. Many regions of Nepal are clearly under sampled, such that future exploration should reveal additional species. The insufficient collections and limited published information present challenges to determining and evaluating distribution patterns of Nepalese ants (Subedi and Budha 2020). However, the checklist presented here provides a waypoint for further studies of diversity and distribution of Nepalese ants.

Dubious and unverified records of ants in Nepal
Thirty-seven ant species reported in AntWiki (2020) and/or AntWeb (2020) and/or antmaps.org are not substantiated by specimens, or literature records and/or are with references unverified. These species are marked as dubious and have been excluded from the main species list. We present them below with explanation of their exclusion (Table 3). Table 3. Dubious and unverified records of ants in Nepal.