The Ants (Hymenoptera:Formicidae) of Rawdhat Khorim Nature Preserve, Saudi Arabia, with Description of a New Species of the Genus Tetramorium Mayr

Zootaxa 3709 (6): 565–580 ISSN 1175-5326 (print edition) www.mapress.com/zootaxa/ Article ZOOTAXA Copyright © 2013 Magnolia Press ISSN 1175-5334 (online edition) http://dx.doi.org/10.11646/zootaxa.3709.6.6 http://zoobank.org/urn:lsid:zoobank.org:pub:10D447D5-D5C0-409F-85FC-6E3E4619C487

The ants (Hymenoptera:formicidae) of Rawdhat Khorim Nature Preserve, Saudi Arabia, with description of a new species of the genus Tetramorium Mayr

MOSTAFA R. SHARAF1*, MAHMOUD S. ABDEL-DAYEM2, HATHAL M. AL DHAFER2 & ABDULRAHMAN S. ALDAWOOD1 King Saud University, College of Food and Agriculture Sciences, Plant Protection Department, P.O. Box 2460 Riyadh 11451, Saudi Arabia. E-mail:[email protected]; [email protected]; [email protected]; [email protected] 1*Corresponding author. E-mail: [email protected] 1Economic Entomology Research Unit (EERU). 2King Saud University Museum of Arthropods (KSMA).

Abstract

Rawdhat Khorim, a densely vegetated alluvial basin supporting a distinctive floral community in the hyper-arid desert of central Saudi Arabia, is one of the most important protected nature sanctuaries of the country. The ant fauna (Formicidae) of Rawdhat Khorim was sampled and 14 species, including one new species were collected using a variety of sampling methods. The new species, Tetramorium saudicum sp. n., a member of the T. caespitum-group, is described based on the worker caste. Cataglyphis viaticoides (André) is recorded for the first time from Saudi Arabia. The information in this paper will allow natural resource managers to establish long-term ecological studies, using sentinel taxa such as ants to evaluate present and future impacts on Rawdhats.

Key words: Saudi Arabia, Formicidae, ant communities, Tetramorium, new species, new records

Introduction

In many regions of the world nature reserves, sanctuaries, and wildlife parks are often the last refuges of biological diversity. Increasing human populations and associated impacts are usually at the expense of natural ecosystems and biological resources. These perturbations often impact even protected or managed landscapes (Likens, 1991; Hobbs and Huenneke, 1992; NCWDC, 2005). The Arabian Peninsula, a region of a unique mixture of Palaearctic, Afrotropical, and Oriental faunal elements is being impacted by rapid population growth and development (Roudi-Fahimi and Kent 2007). As Al Omari (2011) pointed out, protected areas of the Peninsula do not fully reflect the diversity of habitats and species. In the largest country of the Arabian Peninsula, the Kingdom of Saudi Arabia, the central region comprising Riyadh Province includes remarkable ecosystems such as the Al-Dahna Desert and the Towaik Mountains (Zoghet and Al Alsheikh, 1999). Another unique ecosystem of Riyadh Province and environs is known as Rawdhats, the Arabic word for “gardens”. About 130 Rawdhats have been identified in Riyadh Province (Al Mobdel, 2001). These “gardens” are usually densely vegetated alluvial basins or plains that often include vernal ponds and lakes, supporting a distinctive floral community in the hyper-arid deserts of the region (Vesey-Fizberald 1957, Tag El-Din et al. 1994, Shaltout and Mady 1993, Al-Farraj et al. 1997, Alfarhan 2001). However, cities of the region—Riyadh, Buraida, and Al Kharj are rapidly expanding into vast surrounding areas. Overgrazing, woodcutting, motorized vehicle traffic, and even day use activities such as picnicking have recently threatened these Rawdhats (Al-Farraj et al. 1997). One of the largest of these Rawdhats, approximately 95 km northeast of Riyadh, is Rawdhat Khorim (Alfarhan 2001). The insect fauna of these Rawdhats is poorly studied. Usually the dominant insects of these areas are ants. No large-scale ant study has been conducted in any of the Rawdhat areas in Saudi Arabia. The purpose of this paper is to report on the ants of Rawdhat Khorim including the description of a new species.

Accepted by J. Longino: 27 Aug. 2013; published: 10 Sept. 2013 565 The taxonomy of ants known to occur in Saudi Arabia is the result of studies over the last 27 years. The first paper was published by Collingwood (1985), who provided a list and keys to 164 species, 156 of which were recorded for the first time from Saudi Arabia. In addition, this paper provided 146 new ant species records for the Arabian Peninsula. Collingwood (1985) also described ten new species of ants. A more comprehensive treatment of the Formicidae of the Arabian Peninsula is by Collingwood and Agosti (1996) treating 265 species, of which 56 were described as new. In Riyadh Province of central Saudi Arabia, a hyper-arid region where Rawdhat Khorim is situated, 38 ant species have been reported, of which eight were described as new (Collingwood, 1985; Collingwood and Agosti, 1996). Recently, two additional new species were described from this region, Solenopsis saudiensis (Sharaf and Aldawood, 2011) and Plagiolepis boltoni (Sharaf et al. 2011). We report here the results of a new biodiversity survey of the ants of Rawdhat Khorim, contributing to the knowledge of the ants of Saudi Arabia and the Arabian Peninsula. Among the ants collected during the survey a new species of Tetramorium was discovered.

Material and methods

Study area. Rawdhat Khorim is a relatively pristine Rawdhat and is one of the more important protected nature preserves in Saudi Arabia primarily because of the distinctive floral diversity (Al- Farraj et al., 1997; Alfarhan, 2001). Rawdhat Khorim (Fig. 1b) is a rectangular alluvial basin (Vesey-Fizberald, 1957), comprising an area of 24 km2, located about 95 km northeast of Riyadh (25°23'N, 47°17'E, 560 m.a.s.l.) (Fig. 1a). Moisture in this area comes from direct rainfall and from drainage supplied by the adjacent highlands. There is no permanent standing water but temporary pools may occur. Plant growth is higher during spring than in other seasons (Al- Farrajet al., 1997) (Fig. 2a, b). At least 17 different plant communities have been identified in Rawdhat Khorim associated with distinct soil types (Tag El-Din et al., 1994). Alfarhan (2001) listed 153 plant species belonging to 32 families. He stated that the vegetation is largely seasonal, comprised of mostly annual species (82%), with the Asteraceae most abundant. One of the most abundant and widespread species is Matricaria aurea (Loefl.) Sch. Bip. (Asteraceae). Two HOBO Data Loggers (HOBO H8 Family, RH/Temp/Light/External, Therma-Stor LLC, Madison, Wisconsin, USA) were attached to Acacia trees to record temperatures and relative humidity each two hours from October 2011 to January 2013. Rainfall data were obtained from the Worldclim database (http://www.worldclim.org). Hot summers and mild winters characterize the climate of Rawdhat Khorim. The Hobo sensors recorded an average annual temperature of 26 °C and average relative humidity of 33%; Worldclim average annual rainfall was 122 mm (Fig. 3). The hottest months were June to August (35.0–36.3°C) and the coldest months were December to February (14.6–15.7°C). March and April are the wettest months (30 and 28 mm precipitation, respectively), while no precipitation falls from June to September. Sampling procedures. Thirty-four sampling periods (2 trips/month) were carried out from October 2011 to January 2013. A total of 56,326 ants in 14 species were collected by eight techniques (baits, light traps, Malaise traps, pitfall traps, beating, sweeping, hand picking, and using aspirators). Specimens are deposited in the King Saud University Museum of Arthropods, King Saud University, Riyadh, Saudi Arabia. The following abbreviations are used for morphological features and metrics and follow the standard measurements (Csõsz et al. 2007, Hita Garcia et al. 2010, Hita Garcia and Fisher 2011):

TL Total length; outstretched body length from mandibular apex to gastral apex. HL Head length; maximum head length, excluding mandibles. HW Head width; maximum head width in full-face view. SL Scape length, excluding condylar bulb. EL Eye Length; maximum diameter of an eye. PRW Pronotal width; maximum pronotal width in dorsal view. ML Mesosoma length; length of mesosoma in lateral view, from the point where the pronotal dorsum meets the cervical shield to the posterior margin of propodeal lobes or teeth. PL Petiole length; maximum petiolar length in dorsal view, from anterior margin to posterior margin. PW Petiole width; maximum petiolar width in dorsal view. PPL Postpetiole length; maximum postpetiolar length in dorsal view.

ANTS OF RAWDHAT KHORIM Zootaxa 3709 (6) © 2013 Magnolia Press · 567 FIGURE 2. a, one of the water bodies formed after the rainfall inside Rawdhat Khorim. b, general view of the plant cover during the flowering season. (M. S. Abdel-Dayem photos)

568 · Zootaxa 3709 (6) © 2013 Magnolia Press SHARAF ET AL. FIGURE 3. Climate data for Rawdhat Khorim, Central Region, Saudi Arabia (source of temperature and relative humidity: HOBO Data Loggers; rainfall: worldclim database: http://www.worldclim.org/).

PPW Postpetiole width; maximum postpetiolar width in dorsal view. Indices: SI Scape index (SL 100/HW). CI Cephalic index (HW 100/HL).

All measurements are in millimeters. For figures of species, images of representative specimens (not from Rawdhat Khourim) were obtained from AntWeb (www.antweb.org).

Depositories

BMNH The Natural History Museum, London, United Kingdom. CASC California Academy of Science Collection, San Francisco, California, USA. KSMA King Saud University Museum of Arthropods, King Saud University, Riyadh, Kingdom of Saudi Arabia (Holotype depository). MCZC Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA. MHNG Muséum Histoire Naturelle, Geneva, Switzerland. NHMB Naturhistorisches Museum, Basel, Switzerland. SEMC Division of Entomology (Snow Entomological Collections), University of Kansas Natural History Museum, Lawrence, Kansas, USA. WMLC World Museum Liverpool, Liverpool, United Kingdom.

Results

Subfamily Cerapachyinae

Lioponera longitarsus Mayr, 1879: 667. Combination in Cerapachys: Brown, 1975: 237.

This is the second record of this species from Saudi Arabia and for the Arabian Peninsula. The first record of this species was from Abu Arish (southwestern Saudi Arabia) by Collingwood (1985). Cerapachys longitarsus was originally described from India and subsequently recorded from UAE (Collingwood et al., 2011); Egypt (Sharaf, 2006); Philippines, North Australia, and Taiwan (Terayama et al., 1988). At Rawdhat Khorim this species is considered rare, with only four specimens. All are alate males, three attracted to a light trap and one collected by a pitfall trap. They were collected in April, October and November.

Subfamily Formicinae

Camponotus sericeus (Fabricius, 1798) (Fig. 4 c, d)

Formica sericea Fabricius, 1798: 279. Combination in Camponotus: Mayr, 1862: 675.

Camponotus sericeus is one of the more common carpenter ants of the Arabian Peninsula (Collingwood, 1985; Collingwood and Agosti, 1996; Collingwood et al. 2011). It was originally described from Senegal, recorded from Algeria (Santschi 1929a) and has a broad distribution throughout the Afrotropical region (Wheeler 1922, Taylor 2010). Additional records are from Pakistan (Umair et al., 2012), India, and Ceylon (Collingwood, 1962). This species has also been reported from the Oriental region, e.g. Thailand (Jaitrong and Nabhitabhata, 2005). Workers are active throughout Rawdhat Khorim, being abundant from March through October, with a major peak in June. Workers of C. sericeus occur on Acacia trees and on the giant milkweed Calotropis procera (Aiton) W. T. Aiton (Apocynaceae). Several workers have been observed foraging on C. procera plants and attending aphids.

Camponotus xerxes Forel, 1904 (Fig. 4 e, f)

Camponotus maculatus xerxes Forel, 1904: 424. Raised to species: Pisarski, 1967: 414.

This species was reported from Saudi Arabia, Kuwait, United Arab Emirates (UAE) and Oman (Collingwood 1985; Collingwood and Agosti 1996, Collingwood et al. 2011). Foragers are common from March to October with a peak in September. Workers were commonly found foraging on C. procera. The high degree of polymorphism and the large intra- and interspecific variation among the species of Camponotus make determinations often difficult. Camponotus xerxes is closely related to C. fellah Dallah Torre, but can be distinguished by the absence of erect setae on the ventral head surface, whereas in C. fellah there are 1– 10 setae (Ionescu-Hirsch, 2009).

Cataglyphis livida (André, 1881)

Myrmecocystus albicans var. livida André, 1881: 58. Combination in Cataglyphis: Wheeler & Mann, 1916:173. Raised to species: Arnol'di, 1964: 1810.

This species is widely distributed from Egypt to Afghanistan (Radchenko, 1997) and has been reported from all countries of the Arabian Peninsula (Collingwood, 1985; Tigar and Collingwood, 1993; Collingwood and Agosti, 1996; Tigar and Osborne, 1999; Collingwood et al. 2011). Cataglyphis livida is a common species at Rawdhat

FIGURE 4. a, b Cerapachys longitarsus (alate male, type) (CASENT0902740, India); c, d, Camponotus sericeus (CASENT0104896, Guinea); e, f, Camponotus xerxes (after Collingwood et al. 2011, UAE).

Cataglyphis minima Collingwood, 1985: 289.

Currently, C. minima appears to have a more restricted distribution in the Arabian Peninsula than other species of the genus. It was originally described from Saudi Arabia and recorded from UAE (Tigar and Collingwood, 1993). At Rawdhat Khorim, C. minima has an abundance and foraging behavior similar to C. niger.

Cataglyphis niger (André, 1881) (Fig. 5 c, d)

Myrmecocystus viaticus var. niger André, 188l: 56. Combination in Cataglyphis: Emery, 1925:265. Raised to species: Collingwood 1985:290.

This species was originally described from Israel and recorded from Saudi Arabia, Kuwait, Oman and Yemen (Collingwood, 1985; Collingwood and Agosti, 1996), UAE (Collingwood et al. 2011) and Syria (Santschi, 1929b). It is common at Rawdhat Khorim with peak abundance in June and decreasing during cooler months. Workers were collected from the following plants: Acacia gerrardii Benth (Fabaceae), C. procera, Rhazya stricta Decne (Apocynaceae) and Ziziphus nummularia (Burm. f) Wight & Arn. (Rhamnaceae).

Cataglyphis viaticoides (André, 1881)

Myrmecocystus albicans var. viaticoides André, 1881:57.Combination in Cataglyphis: Emery, 1925:263. Raised to species: Arnol'di, 1964:1809.

The collection of this species at Rawdhat Khorim represents the first record known for Saudi Arabia and the second record for the Arabian Peninsula. Collingwood et al. (2011) reported it from UAE. At Rawdhat Khorim, C. viaticoides is a common species found throughout the year and abundant from June to October, with a peak in September. Cataglyphis viaticoides was often observed foraging on C. procera.

Lepisiota simplex (Forel, 1892)

Acantholepis simplex Forel, 1892: 43. Combination in Lepisiota: Bolton, 1995:228.

This widespread species was described from Somalia (Forel, 1892) and recorded from Zimbabwe (Forel, 1913) and India (Bingham, 1903). Within the Arabian Peninsula it is apparently restricted to Saudi Arabia (Collingwood, 1985). It is a common species at Rawdhat Khorim, abundant from April to September and declining in numbers from October to March.

Subfamily Myrmicinae

Messor ebeninus Santschi, 1927 (Fig. 5 e, f)

Messor semirufus var. ebeninus Santschi, 1927: 229. Raised to species: Tohmé, 1971: 569. Junior synonym of Messor semirufus: Baroni Urbani, 1974: 227. Revived from synonymy: Tohmé & Tohmé, 1981:142.

This species is widely distributed throughout the Arabian Peninsula (Collingwood, 1985, Collingwood and Agosti, 1996). At Rawdhat Khorim, worker activity has two peaks of abundance, in April and December, decreasing from July through October.

572 · Zootaxa 3709 (6) © 2013 Magnolia Press SHARAF ET AL. FIGURE 5. a, b Cataglyphis minima (CASENT0249862, Saudi Arabia), c, d, Cataglyphis niger (CASENT0280330, Yemen); e, f, Messor ebeninus (CASENT0249861, Saudi Arabia); g, h, Monomorium mayri (CASENT0249904, India).

Monomorium gracillimum var. mayri Forel, 1902: 209. Raised to species, senior synonym of Monomorium karawajewi Wheeler: Bolton, 1987: 326.

Monomorium mayri is considered one of the most common ant species of the Arabian Peninsula. It has been reported from Saudi Arabia, Oman and Yemen (Collingwood, 1985; Collingwood and Agosti, 1996), and UAE (Tigar and Collingwood, 1993). Monomorium mayri, a common species at Rawdhat Khorim, exhibits high abundances from April to October, peaking in June and slowly declining from November to March.

Solenopsis saudiensis Sharaf & Aldawood, 2011 (Fig.6 a, b)

Solenopsis saudiensis Sharaf & Aldawood, 2011: 476.

This species was recently described from Riyadh, Saudi Arabia (Sharaf and Aldawood, 2011) and was the first record of the genus from the country. Recently, the Solenopsis of the Arabian Peninsula were revised by Sharaf and Aldwood (2012). At Rawdhat Khorim this species is rare, with only a single specimen collected by a pitfall trap in February.

Genus Tetramorium Mayr, 1855

Tetramorium is one of the most diverse ant genera in the subfamily Myrmicinae, with 518 described taxa (Bolton, 1995; Bolton et al., 2007; Bolton 2013), distributed worldwide in the tropics and temperate regions (Brown, 2000). The genus has been comprehensively revised for the majority of the zoogeographic regions (Bolton 1976, 1977, 1979, 1980, 1985; Hita Garcia et al., 2010; Hita Garcia & Fisher 2011, 2012a, 2012b). For many years, the Palaearctic region was lacking revisions but recently several important contributions have been published (Steiner et al., 2005; Schlick-Steiner et al., 2006; Csõsz et al., 2007; Csõsz & Schulz, 2010; Steiner et al., 2010).

Tetramorium chefketi Forel, 1911 (Fig.6 c, d)

Tetramorium caespitum var. chefketi Forel, 1911:332. Raised to species: Agosti & Collingwood, 1987: 56. Senior synonym of Tetramorium turcomanicum: Csõsz, Radchenko & Schulz, 2007: 18.

This species was recorded from Saudi Arabia (Collingwood, 1985), Oman and Yemen (Collingwood and Agosti, 1996). Outside Arabia, it has been reported from several parts of the Palaearctic region including southern Europe (Greece, Bulgaria, Macedonia, Romania), southern Ukraine, south of western Russia, northwestern Caucasus, Turkey, Turkmenistan, northern Kazakhstan, southeastern Siberia, to the east to Kyrgyzstan and Altai Mountains (Csõsz et al., 2007). At Rawdhat Khorim this species is relatively common and observed foraging on Ziziphus nummularia (Burm. f) Wight & Arn. (Rhamnaceae). The species has two abundance peaks, in June and November. It was collected using pitfall traps and beating vegetation.

Tetramorium saudicum Sharaf sp. n. (Fig.6 e, f, g)

Holotype worker. Saudi Arabia, Riyadh, Rawdhat Khorim, 24.III.2012, 25.23°N, 47.17°E, 559 m (M. R. Sharaf); unique specimen identifier CASENT0281582, deposited at KSMA.

574 · Zootaxa 3709 (6) © 2013 Magnolia Press SHARAF ET AL. FIGURE 6. a, b, Solenopsis saudiensis (CASENT0249866, Saudi Arabia); c, d, Tetramorium chefketi (CASENT0906711, Bulgaria); e, f, g, Tetramorium saudicum sp. n. (CASENT0281582, Saudi Arabia); h, i, Tetramorium sericeiventre (CASENT0102388, Madagascar).

ANTS OF RAWDHAT KHORIM Zootaxa 3709 (6) © 2013 Magnolia Press · 575 Paratypes: 21 workers, same data as the holotype; 2 workers, Saudi Arabia, Jazan, Al Zabia 9.IV.2012, 17.06°N, 42.39°E, 43 m (M. R. Sharaf); 2 workers, Shaqiq Shamran, IV.1983 (C. A. Collingwood); 2 workers, Riyadh, III.1989 (soil fauna); 15 workers, Riyadh, Rawdhat Khorim, [multiple dates]; one paratype deposited in each of the following museums: MHNG, NHMB, CASC, MCZC, SEMC, WMLC, BMNH, and the remaining specimens at KSMA. Holotype worker: TL 3.12; HL 0.80; HW 0.80; SL 0.55; EL 0.22; PRW 0.52; ML 0.87; PL 0.22; PW 0.25; PPL 0.22; PPW 0.30; Indices: SI 69; CI 100. Paratype workers: TL 3.12–3.25; HL 0.75–0.85; HW 0.75–0.80; SL 0.50–0.55; EL 0.20–0.25; PRW 0.50– 0.55; ML 0.85–0.92; PL 0.17–0.22; PW 0.25–0.27; PPL 0.17–0.22; PPW 0.25–0.30; Indices: SI 63–71; CI 91–100 (11 measured). Diagnosis. Tetramorium saudicum is a member of the caespitum-group. It can be readily separated from its closest congener, the Palaearctic T. striativentre Mayr, 1877 from Kazakhstan by the bicoloured body, head, mesosoma, waist and appendages reddish brown, gaster brownish or blackish brown; whereas T. striativentre is unicolorous brownish and the appendages are pale brown. Both species are similar in body size, mesosomal and gastral sculpture, and the frontal carina that extend back to the posterior margins of eyes. Tetramorium saudicum also differs from T. striativentre by the following: the head dorsum is polished with few (nearly 10) fine longitudinal rugulae superimposed upon irregularly punctulate ground-sculpture while in T. striativentre, the head dorsum is dull with numerous (nearly 20) very fine longitudinal rugulae superimposed upon a finely and densely punctulate or granular ground-sculpture. In addition, the petiolar node of T. saudicum in dorsal view is clearly irregularly rugulose, whereas in T. striativentre the petiolar node in dorsal view is clearly regularly longitudinally rugulose. Tetramorium saudicum can be distinguished from the remaining Arabian species of the genus (except T. sericeiventre and T. khyarum) by the sculptured first gastral tergite. It can be separated from T. sericeiventre and T. khyarum by the following characters: the scape index is much smaller, SI 63–71 (versus SI 113–118 for khyarum and SI 101–118 for sericeiventre); the head length is smaller, HL 0.75–0.85 (Versus HL 0.96–1.00 for khyarum and HL 0.80–1.00 for sericeiventre) and eyes relatively larger, EL 0.20–0.25 (versus EL 0.20 for khyarum and EL 0.16–0.22 for sericeiventre). Description of worker. Head: Head as long as wide or subequal, with convex sides and nearly straight posterior margin; anterior clypeal margin entire; ventral surface of head with few ammochaete setae; frontal carinae present, running back beyond level of posterior margin of eyes but feebly developed throughout their length and weaker behind eyes than in front; eyes large (EL about 0.29 x HW) with about 15 ommatidia in longest row; ventral margin of eyes more or less flat, anterior, dorsal and posterior margins curved so that eyes in profile resembling reclinate letter D; mandibles longitudinally rugose; antennae 12-segmented; antennal scrobes absent; entire dorsum and profile of head very finely and very densely longitudinally costulate, spaces between costulae finely, irregularly and densely punctulate; dorsum of head with many paired hairs. Mesosoma: Outline of dorsal mesosoma unbroken in profile; pronotal humeri sharply angulate; metanotal groove not impressed; propodeal spines acute and strongly developed; dorsal (outer) surface of hind tibiae with appressed pubescence; propodeal dorsum with a single pair of short hairs; mesosoma strongly longitudinally rugulose, space between regulae smooth and shining. Waist: Petiole cuboid; petiolar and postpetiolar nodes in dorsal view distinctly broader than long; petiole with one pair of hairs, postpetiole with three pairs of hairs; petiolar node in dorsal view clearly irregularly rugulose; postpetiolar node distinctly strongly longitudinally rugulose. Gaster: First gastral tergite longitudinally, very finely and very densely striated, appearing dull; gaster with scarce scattered erect hairs and moderately dense appressed pubescence. Bicoloured species, head, mesosoma, petiole, postpetiole and appendages reddish brown, gaster brownish or blackish brown. Etymology. The name of this species, saudicum, refers to the type locality, the Kingdom of Saudi Arabia. Habitat. Tetramorium saudicum was observed nesting directly in the ground and many workers were observed carrying dry plant seeds.

Tetramorium sericeiventre Emery, 1877 (Fig.6 h, i)

Tetramorium sericeiventre Emery, 1877:370.

576 · Zootaxa 3709 (6) © 2013 Magnolia Press SHARAF ET AL. This is the most common Tetramorium species found in the Arabian Peninsula (Collingwood, 1985; Collingwood and Agosti, 1996; Collingwood et al. 2011) and is also broadly distributed in the savannah of tropical Africa. In Rawdhat Khorim, this species is very common and occurs during all months of the year, with a peak in December. It was observed foraging on C. procera.

In the key to Arabian species (Sharaf et al. 2012:7) T. saudicum will key to couplet 16 along with chefketi and syriacum. Couplet 16 is modified here to separate the three species.

16. Mesosomal pilosity restricted to pronotum and first half of mesonotum, propodeum bare; SL 0.78–0.87; petiolar and postpetiolar nodes coarsely sulcate (Russia & Arabia) ...... chefketi - Mesosoma with abundant, stout and relatively long suberect hairs; SL 0.70–0.77; petiolar and postpetiolar nodes irregularly sculptured (Middle East) ...... syriacum - Mesosomal pilosity fine and acute apically and restricted to mesonotum, propodeal dorsum with a single pair; SL 0.50–0.55; petiolar node clearly irregularly rugulose; postpetiolar node distinctly strongly longitudinally rugulose (Saudi Arabia)...... saudicum sp. n.

Discussion

Saudi Arabia occupies an important biogeographical position at the junction of Palaearctic, Afrotropical, and Oriental zoogeographical regions (Buttiker, 1979; Larsen, 1984a; Mordan, 1984). The desert region between Palaearctic and Afrotropical regions is known as the Eremic zone (Uvarov, 1938; Greathead, 1980; Larsen, 1984b), the Saharo-Arabian subregion (Takhtajan, 1986), or the Afroeremic zone (De Lattin, 1967). Like other regions of Saudi Arabia and the Arabian Peninsula, in the Riyadh Region, including Rawdhat Khorim, few comprehensive faunal surveys have been carried out to document the myrmecofauna. Only ten ant species have been previously described from this region: Tetramorium juba and Camponotus arabicus (Collingwood, 1985); Monomorium harithe, M. hemame, M. suleyile, M. riyadh, Lepisiota riyadha, and Cataglyphis holgerseni (Collingwood and Agosti 1996); Solenopsis saudiensis (Sharaf and Aldawood, 2011); and Plagiolepis boltoni (Sharaf et al., 2011). From the present study, it is obvious that most ant species recorded from Rawdhat Khorim are taxa with Palaearctic affinities. This is also true for the entire Riyadh Region based on recent collections by the senior author. From the 14 recorded species, eleven have a Palaearctic eremic origin (> 71%), whereas only three are shared between Palaearctic and Afrotropical regions: Camponotus sericeus, Lepisiota simplex, and Tetramorium sericeiventre. This paper provides the first taxonomic survey of the ants of a unique seasonal mesic habitat, a Rawdhat, in the hyper-arid deserts of central Saudi Arabia. Fourteen ant species, including one new species, were collected from Rawdhat Khorim. Ants are considered excellent indicators of habitat quality and disturbance (Alonso and Agosti 2000). This study is a contribution that provides the taxonomic basis for one of the most abundant and important faunal components of Rawdhats. Hopefully, this information will allow natural resource managers to establish long-term ecological studies, using sentinel taxa, such as ants, to evaluate present and future impacts on these remarkable “gardens” found in deserts of the region.

Acknowledgments

This work was supported by Project No. 10-ENV1291, National Science and Technology Innovation Plan, King Saud University, with King Abdulaziz City for Science and Technology. The authors are grateful to John Longino, Francisco Hita Garcia and an anonymous referee for valuable comments and suggestions that helped to improve this article. Special thanks go to the research team of the KSMA for collecting the specimens. We are much indebted to Barry Bolton for the long discussion and useful information on the new species and Boris Kondratieff for critical reading of the manuscript. Thanks go to Brian Fisher for generous permission to use species images from Antweb and to Michele Esposito and Estella Ortega (California Academy of Sciences, San Francisco) for photographing the new species. Mostafa Sharaf thanks Hoda Farid (Professor, Ain Shams University, Cairo) and Sasha Li (San Francisco) for continuous encouragement.

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