An update to the taxonomy and distribution of the Arabian Tapinoma Foerster, 1850 (Hymenoptera: Formicidae) with an illustrated key and remarks on habitats

Abstract Background Tapinoma Foerster belongs to the ant subfamily Dolichoderinae and the vast majority of its species are arboreal or generalised foragers. The genus is composed of 70 described species, 22 known subspecies and six valid fossil species worldwide, while from the Arabian Peninsula, three species have been recorded so far. New information Ants of the genus Tapinoma of the Arabian Peninsula are reviewed, keyed and illustrated, based on the worker caste. Three species are diagnosed, T. melanocephalum (Fabricius, 1793), T. simrothi Krausse, 1911 and T. wilsoni Sharaf & Aldawood, 2012. We present the first illustrated key to the Arabian Tapinoma, enhanced by automontage images to facilitate species recognition. New distributional data for species are presented, based on recently-collected material from the region and literature records. Information on habitats' preference and biology of species are given.


Introduction
The Arabian Peninsula, in western Asia, covers a surface area of 3.2 million km comprising Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates (UAE) and Yemen (Fig. 1). It turns out to be a very interesting biogeographic area, since it straddles the Afrotropical, the Palaearctic and, to a lesser extent, the Oriental realms (Larsen 1984, Hölzel 1998. With its location at the interchange of three biogeographic realms, the Arabian Peninsula shares faunal elements from those three Regions (Zunino and Zullini 1995, Abdel-Dayem et al. 2018, Ziani et al. 2019, Abdel-Dayem et al. 2020, Letardi et al. 2020. Several faunistic contributions have shed light on zoogeography of the Arabian ants, indicating the predominance of Afrotropical species in the south-western mountains of the Arabian Peninsula and extending southwards to Yemen and eastwards to the Dhofar Province of Oman. While the species from the Palearctic prevail outside this mountainous range including the vast desert regions of the central and northern Arabia, in addition to the countries of the eastern region (Kuwait, Bahrain, Oman, Qatar and UAE) (Collingwood 1985, Collingwood and Agosti 1996, Collingwood et al. 1997, Collingwood et al. 2011, Sharaf et al. 2014, Sharaf et al. 2018, Sharaf et al. 2020a, Sharaf et al. 2020b). The genus Tapinoma was described with the type-species T. collina (junior synonym of Tapinoma erraticum), by monotypy (Foerster 1850). With 71 described species, 24 known subspecies and six valid fossil species, Tapinoma is one of the largest genera of the subfamily Dolichoderinae (Bolton 2021). The vast majority of species are arboreal (Shattuck 1992) or generalised foragers (Brown 2000), with a remarkable preference for attending honeydew-producing insects (Venkataramaiah and Rehman 1989).
The genus was recorded and keyed for the first time from the Arabian Peninsula by two species, Tapinoma melanocephalum (Fabricius 1793) and T. simrothi Krausse 1911, collected from the Kingdom of Saudi Arabia (KSA) and Oman (Collingwood 1985). The faunal study of the ant species of the Arabian Peninsula (Collingwood and Agosti 1996) reported T. melanocephalum from Yemen and T. simrothi from Kuwait and Yemen. Tapinoma melanocephalum and T. simrothi were collected from UAE by Collingwood et al. (1997), Collingwood et al. (2011). The rare species T. wilsoni Sharaf & Aldawood, 2012 was described from the Al Sarawat Mountains of Saudi Arabia, based on the worker caste (Sharaf et al. 2012). Recently, Al-keridis et al. (2021) described the queen of T. wilsoni and presented the first key of the Arabian Tapinoma, based on the queen caste. More recently, Sharaf et al. (2020b) reported T. melanocephalum and T. simrothi from the State of Qatar.
Tapinoma melanocephalum and T. simrothi, are widely spread either in urban sites or wild habitats of the Arabian Peninsula, including agricultural fields and date palm farms (Collingwood 1985). The two species are frequently collected by research projects concerned with the environment and agriculture of the Region (Sharaf et al. 2012). Due to the documented relationships between numerous dolichoderine ants (e.g. T. simrothi) and a wide range of sap-sucking insects, such as mealybugs (e.g. Aldawood 2011, Xu et al. 2019) and aphids (e.g. Addicott 1978, Venkataramaiah andRehman 1989), ecological and biological studies of these ant species are necessary from an agricultural perspective, since it is likely that they contribute in the protection and distribution of such agricultural pests.
The aims of this study are to provide an illustrated key to facilitate Tapinoma species recognition, study the geographical distribution of species and give notes on species habitat preference.

Materials and methods
In total, 457 specimens were collected from countries of the Arabian Peninsula (Suppl. material 1) using different collecting techniques including hand picking (HP), Light trap (LT), Malaise trap (MT), pitfall trap (PT), sifting tray (SF), sweeping net (SW) and Yellow Pan trap (YPT). Specimens were examined using a stereomicroscope Leica M205 with an optical resolution of 0.952 µm, 20.5:1 zoom, 7.8x to 160x magnification and up to 1050 lp/ mm resolution (with 2.0x objective). Digital colour images of each species were taken using a Leica DFC450 digital camera with a Leica Z16 APO microscope and LAS (v.3.8) software. The images are available online on AntWeb (http://www.AntWeb.org) and are accessible through unique specimen identifiers (e.g. CASENT0906356). The species

Diagnosis
Worker. This is an easily recognised species by its bicoloured body (Fig. 2a, b), with head and mesosoma pale brown to dark brown, antennae, maxillary palps and mandibles pale brown to yellow, gaster and legs pale yellow. Head in full-face view with scapes, when laid back from their insertions, surpass posterior margin of head (Fig.  2c); eyes located in front of mid-length of head (Fig. 2c). The size is small (1.20-1.90 mm) and mesosoma is without dorsal hairs.  (Collingwood 1985); Al Qatif, (Collingwood 1985

Distribution
Tapinoma melanocephalum is a widely distributed invasive species that is spread by human commerce especially in the Tropics and Subtropics of the Old and New Worlds (Wetterer 2009) with an unknown native range. The species is widely spread in several countries of the Arabian Peninsula, including SA and Oman (Collingwood 1985), Yemen (Collingwood and Agosti 1996), UAE (Collingwood et al. 1997), the Socotra Archipelago (Sharaf et al. 2017) and, recently, it has been reported from Qatar (Sharaf et al. 2020b).

Ecology
The species inhabits a broad range of habitats worldwide (Sharaf et al. 2017), including both humid and dry soil of wild and urban localities, in homes, restaurants, hospitals, well-heated buildings and greenhouses (Wetterer 2009), under bark and stones, in leaf litter and sometimes nests are built in walls and potted plants indoors (Smith andWhitman 1992, Ellison et al. 2012), in moist soil of lawn and grasses and under debris (Oster and Wilson 1978) or in opportunistic places (Hölldobler and Wilson 1990). In the Socotra Archipelago (Yemen), the species was observed foraging on a tree located on a mountainside next to a stream drainage where the soil was moist and the area was dominated by the ponerine ant, Brachyponera sennaarensis (Mayr, 1862) and Adiantum capillus-veneris L. (Pteridaceae) (Sharaf et al. 2017). It also inhabits localities rich in organic matter of animal faeces in date palm plantations (Phoenix dactylifera L.) (Sharaf et al. 2017). Workers attend honeydew-excreting insects for honeydew (Venkataramaiah and Rehman 1989) and also feed on both dead and live insects and when disturbed workers are running erratically and rapidly. (Smith 1965).

Diagnosis
Worker. Head in full-face view with strongly convex sides and nearly straight posterior margin (Fig. 3c); anterior central margin with a median well-defined notch, deeper than broad; with head in full-face view, scape surpassing posterior margin of head by about one third of its length (Fig. 3c); metanotal groove distinct (Fig. 3a); propodeal dorsum short, meeting declivity at an obtuse angle; colour uniform dark brown to black, tarsi yellow-brown; whole body covered with appressed pubescence (Fig. 3a, b).

Ecology
In SA, T. simrothi was found nesting amongst roots of lawns, attending mealybugs and co-existing with Solenopsis abdita (Sharaf and Aldawood 2011). The species also attends Aphis gossypii Glover, 1877 for honeydew and the latter gains protection from predators in return (Karami-jamour et al. 2018

Diagnosis
Worker. Head in full-face view longer than broad with shallowly convex posterior margin and sides; anterior clypeal margin broadly and distinctly concave; scapes, in full-face view, surpass posterior margin of head by about 1/6 of its length; all funicular segments distinctly longer than broad (Fig. 4c); metanotal groove indistinct; propodeum in profile with the transition from dorsum to declivity sharply defined, the declivity concave and the angle with a raised apex (Fig. 4a); colour yellow to brown-yellow, antennae and legs uniform yellow (Fig. 4a, b).

Distribution
Saudi Arabia.

Ecology
Tapinoma wilsoni was found foraging on the ground surface of a Banana farm in Dhi Ayn Archeological Village, a semi-isolated area that is completely surrounded by high mountains of the Al Sarawat Mountains (KSA) and the soil is clay and humid (Sharaf et al. 2012). Nothing is known about the biology of the species. The species is co-existing with the ant species Carebara arabica (Collingwood & van Harten, 2011), Tetramorium sericeiventre Emery, 1877, Pheidole minuscula Bernard, 1953, Trichomyrmex destructor (Jerdon, 1851 and Monomorium exiguum Forel, 1894.

Identification keys
Key to the Arabian species of the genus Tapinoma 1 Propodeum in profile with the transition from dorsum to declivity sharply defined, the declivity concave and the angle with a raised apex (Fig. 5a) T. wilsoni Sharaf & Aldawood -Propodeum in profile with the transition from dorsum to declivity has a rounded angle (Fig. 5b)

Discussion
Amongst the three Arabian Tapinoma species, T. simrothi is the most widespread species, followed by T. melanocephalum, whereas T. wilsoni is the rarest species with a limited geographic distribution confined to the type locality (Dhi Ayn Archeological Village) at the Al Sarawat Mountains, KSA) (Figs 6, 7, 8). The wide geographic distribution of T. melanocephalum is related to the broad habitat preference of the species (Smith 1965, Oster and Wilson 1978, Venkataramaiah and Rehman 1989, Hölldobler and Wilson 1990, Smith and Whitman 1992, Wetterer 2009, Ellison et al. 2012, Sharaf et al. 2017. Tapinoma simrothi is broadly distributed, especially in public gardens and agricultural fields of the Central Region of the Arabian Peninsula and with apparent associations with the sapsucking insects for honeydew (Collingwood et al. 2011, Sharaf andAldawood 2011). The species is also widely spread in the wild sites of the deserts in Riyadh Province, especially near to Acacia trees. The ability of species to inhabit both urban and wild habitats of the Arabian Peninsula identifies the wide geographic distribution.