A New Ant Species of the Genus Tetramorium Mayr, 1855 (Hymenoptera: Formicidae) from Saudi Arabia, with a Revised Key to the Arabian Species

Tetramorium amalae sp. n. is described and illustrated from Saudi Arabia based on two worker caste specimens collected in Al Bahah region. The new species belongs to the T. shilohense group and appears to be closely related to T. dysderke Bolton from Nigeria. T. amalae is distinguished by having well-developed frontal carinae, smaller eyes, greater head length and width, greater pronotal width, and the petiole node is longer than broad. Tetramorium latinode Collingwood & Agosti is recorded for the first time from Saudi Arabia and for only the second time since the original description. The worker caste of T. latinode is redescribed and illustrated using scanning electron micrographs to facilitate recognition and the gyne is described for the first time with observations given on species relationships, biology and habitat. A revised key to the nineteen Tetramorium species recorded from Arabian Peninsula based on worker castes is provided. Tetramorium bicarinatum (Nylander) is recorded for the first time from Saudi Arabia. It is suggested that T. amalae and T. latinode are endemic to the Arabian Peninsula.


Introduction
The ant genus Tetramorium is one of the largest hyperdiverse ant genera in the subfamily Myrmicinae. It contains more than 400 species and subspecies worldwide [1] and is distributed through the tropics and temperate regions [2]. Most Tetramorium species nest in decaying wood, leaf-litter, or directly into the soil [3] with many Arabian species nesting into open hard-packed earth under stones. Other species are known to be arboreal or termitolestic in Africa [3]. The world Tetramorium fauna was comprehensively revised for all zoogeographical regions except the Palaearctic region by Bolton [3][4][5][6][7] with additions by Radchenko [8,9] for the former Soviet Republics, Hita Garcia et al. on some species-groups of the Afrotropical [10][11][12] and Malagasy [13] areas, Yamane & Jaitrong [14] on Laotian species, also Csösz et al. [15] and Csösz & Schulz [16] on Palaearctic species.
Within the subfamily Myrmicinae, almost all workers of the genus Tetramorium can be easily recognized by the following combination of characters [17]: lateral portion of clypeus raised into a sharp ridge or shield wall on each side, in front of the antennal insertions; sting with an apicodorsal lamellate appendage projecting from the shaft; either median clypeal carina or median cephalic carina usually present, or both present; palp formula predominantly 4, 3; mandibles armed with three or four teeth apically, followed by a variable number of denticles; antennae 11-or 12-segmented with a 3-segmented club; and with the metanotal groove usually impressed.
Bolton [3] recognized 19 species groups of Tetramorium, and in this paper we treat the species from the Arabian Peninsula (referred to as ''Arabia'' hereafter) as being in his T.shilohense and squaminode groups. The T. shilohense group is distinguished by the following combination of characters: antennae with 12 segments; mandibles usually sculptured; frontal carina varying from strongly developed to absent; antennal scrobes from moderately developed to absent; eyes small to minute with maximum diameter less than 0.176HW; and the propodeum armed with a pair of spines or teeth. The T. squaminode group is distinguished by the following combination of characters: antennae with 12 segments; anterior clypeal margin usually undented medially; frontal carina strongly developed, reaching back almost to posterior margin of head; antennal scrobes present; petiole squamiform, much higher than long in profile and much broader than long in dorsal view; postpetiole usually rounded nodiform; and sculpture predominantly absent from the petiole and postpetiole.
Little is known regarding the genus Tetramorium in Arabia as a whole. The present knowledge of these species is available in only two publications summarizing the taxa known from Saudi Arabia [18] and Arabia [19]. For Saudi Arabia, thirteen species have been recorded [18] two of which were described as new, T. jizani Collingwood from Fayfa and Abu Arish and T. juba Collingwood from Al Kharj and Al Kola. Sixteen species were listed and keyed for Arabia [19] and two additional species were described from Yemen, T. latinode from Mabar and T. yemene from Sid el Feyhn. A new species, T. hirsutum Collingwood & van Harten [20] was described from Yemen based on workers and queens. Three tramp species, T. lanuginosum Mayr, T. simillimum (F. Smith) and T. caldarium (Roger) were recorded from Socotra Archipelago [21]. T. latinode was described from a single worker. The original description is not adequate to distinguish the species, not even indicating the body colour, a character useful to distinguish it from T. squaminode Santschi, its congener. A comprehensive redescription of T. latinode using scanning electron micrographs is presented here.
In the present study, a new species of the genus, T. amalae is described from Saudi Arabia. General information on the habitat and affinities of the new species are given. The tramp species T. bicarinatum is recorded for the first time in Saudi Arabia. A revised key to the known Tetramorium species of Arabia is given, although it is our intention to produce a more comprehensive version when a full set of modern images can be completed and, where necessary, type material examined. All measurements are in millimeters and follow standard measurements [3,13]. As absolute sizes are known to vary within and between samples of some ant species, indices, such as CI, often are more reliable for separating species with otherwise similar morphology and characters.

Measurements and indices
No specific permits were required for the described field studies or for the surveyed locations which are not privately-owned or protected in any way or do not have endangered or protected species.

Nomenclatural Acts
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In addition, this published work and the nomenclatural acts it contains have been registered in ZooBank, the proposed online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix ''http://zoobank.org/''. The LSID for this publication is:urn:lsid:zoobank.org:pub:63028708-CD01-4126-BF88-43E3800CB8A4

Results
Tetramorium amalae Sharaf & Aldawood n. sp.  Fig. 1). Frontal carinae relatively short and weakly developed but distinctly stronger than the other cephalic sculpture, diverging from the frontal lobes and ending at the level of the eyes (Fig. 1). Antennal scrobes visible only as a shallow depression. Eyes tiny ( Fig. 2), consisting of only two minute ommatidia on each side, one is smaller than the other and has diameter approximately 0.01, about 0.016HW and only distinguished under higher magnification. Antennae 12-segmented. Metanotal groove (Fig. 3) feebly impressed. Propodeal spines short and triangular (Fig. 3). Metapleural lobes triangular. Mesosoma sides with irregular wavy longitudinal sculpture (Fig. 4). Propodeal spiracles well developed and circular (Fig. 4). Petiole node rectangular in profile (Fig. 5), with a roughly right-angular anterodorsal angle and oblique posterodorsal angle. In dorsal view the petiole and petiole nodes are distinctly longer than broad, the latter is oblong. Dorsum of head (Figs. 1 and 6) finely but distinctly irregularly longitudinally rugulose, the space between the rugulae finely punctulate. Mesosoma with a faint and low transverse ridge on the anterior pronotum. Promesonotum finely longitudinally rugulose, mesonotum smooth, propodeal dorsum very faintly longitudinally striated. Dorsal surfaces of petiole and postpetiole nodes unsculptured. Gaster smooth and shining. All body surfaces with barbulate    numerous fine hairs, the head pilosity is shorter than on the mesosoma and gaster. Colour uniformly yellow.

Habitat and Biology
The type locality (Figs. 9 and 10) is a relatively pristine area. This new species was collected after a season of a relative low rain fall with sparse vegetation cover. It is worth mentioning that in some years heavy rains occur and then usually accompanied by extensive flooding which greatly increases the density of the vegetation (Fig. 10). Nothing is known of the biology of this species. The holotype and the paratype specimens were found in leaf litter samples.

Etymology
The patronym has been selected to honor both Amal El Saadany (wife of the senior author MRS) and Amal Aldawood (daughter of the second author ASA).

Diagnosis
T. amalae is a member of the T. shilohense-group and appears to most resemble T. dysderke Bolton [3], described but not illustrated, from Nigeria, in body size and colour but differs in having greater head length, HL 0.71 versus 0.59; greater head width, HW 0.61 versus 0.50; and, greater pronotal width, PW 0.42 versus 0.34; the scape index is smaller, SI 72 versus 80 and the eyes are much smaller, EL 0.016HW versus EL 0.066HW. T. amalae has more or less well developed frontal carinae which are stronger than the cephalic sculpture whereas in T. dysderke they are very feebly developed and not stronger than the other cephalic sculpture. In addition, in dorsal view the petiole node in T. amalae is longer than broad whereas it is about as long as broad in T. dysderke. T. amalae is also very similar to T. subcoecum Forel from Kenya in colour, body measurements and general aspects but they can be separated by the following: antennal scrobes visible only as shallow depression in T. amalae whereas no antennal scrobes in T. subcoecum; eyes tiny in T. amalae, about 0.016HW, consisting of two ommatidia, whereas in T. subcoecum eyes little bit bigger, about 0.04-0.066HW consisting of a single ommatidia. Another similar but easily distinguishable species is the West African T. jugatum Bolton, illustrated by Taylor [22]. Although of a similar size and proportions, that has multi-faceted eyes and more pronounced    Redescription of Worker (Figs. 13,14,15,16,17,18,19,20). Head longer than broad with convex sides. Anterior clypeal margin with a median notch or impression. Mandibles faintly longitudinally striated (Fig. 13). Frontal carinae long and sinuate, reaching back almost to the posterior margin of head where they merge with the remaining cephalic dorsum (Figs. 13 and 14). Antennal scrobes distinct (Fig. 14). Eyes large (EL 0.12-0.17) consisting of ten ommatidia in the longest row (Fig. 14).Antennae 12-segmented. Posterior margin of head straight (Fig. 13). Dorsum of mesosoma in profile a continuous curve (Fig. 15). Metanotal groove very feebly impressed (Fig. 15). Propodeal spines elongate and strong, metapleural lobes low and triangular (Fig. 16). Petiole squamiform (Fig. 17), much higher than long in profile and with acute pointed node, in dorsal view (Fig. 18) much broader than long but slightly narrower than the postpetiole which is also clearly broader than long. Postpetiole in profile (Fig. 17) lower than petiole and broadly rounded. Dorsum of head and mesosoma irregularly but quite densely longitudinally rugulose with a reticulum pattern (Fig. 19). Petiole dorsum smooth and shining, postpetiole dorsum more or less smooth and shining with vestiges of patchy pattern (Fig. 18). Gaster smooth and shining. All dorsal surfaces of head and body densely clothed with long, fine, soft finely barbulate hairs (Fig. 20) which are relatively less dense on mesosoma and waist. Antennae and tibiae with dense decumbent pubescence. Colour yellow, the gaster brownish yellow.

Habitat and Biology
T. latinode was originally collected from the Amadan Forest, part of Al Bahah Province (Al Mandaq governorate) about 50 km from Al Bahah to the north. The area is characterized by a substantial degree of endemicity and relatively dense vegetation which differs seasonally depending on rain fall. This vegetation is mainly composed of wild Olive trees, Acacia, juniper, and other plants. Our specimens were taken from a nest under a stone on hardpacked soil and close to a large Juniperus tree. The nest contained tens of workers and the single alate gyne. The nest was found in relatively elevated area of a valley which is high enough to avoid direct impacts of flooding. No additional nests were found despite extensive surveys. In addition, we were not able to collect foraging workers near the nest.

Diagnosis
T. latinode is a member of the T. squaminode group and Collingwood & Agosti [19] suggested close affinities with T. squaminode, described from Tanzania. We consider T. latinode is more closely related to T. akermani Arnold described and illustrated from South Africa [23,6]. T. latinode is yellowish with a brownish yellow gaster, whereas T. akermani is dark brown to blackish brown. In addition, the mandibles are faintly longitudinally striated in T. latinode, whereas they are smooth and shining in T. akermani. T.latinode consistently has a smaller head length HL 0.67-0.80 versus 0.88-0.94; smaller head width HW 0.60-0.72 versus 0.82-0.88, smaller mesosomal length ML 0.70-1.00 versus 0.98-1.08 and smaller eye length EL 0.12-0.17 versus 0.20-0.21. The queen (Figs. 11 and 12) can be compared with the T. squaminode queen shown at http://antbase.org/ants/africa/ tetramorium/tetramorium_squaminode/tetramorium_squaminode. htm. Like the worker that has a longer more rectangular head.       [20] and seen their poor sketch, we find it impossible to place hirsutum accurately in a group. It is valid to include it in the list of species as ''unplaced to group''.

Discussion
With these two species, T.amalae and T. latinode, the T. shilohense group is recorded for the first time in Arabia and the squaminode group also is recorded for the first time from Saudi Arabia. T. latinode was originally described from Yemen. Both species groups are mainly Afrotropical in distribution [3] with seven and thirteen species for the shilohense and squaminode groups, respectively. Apparently, these two species are endemic to the chain of Alsarawat Mountains which extends to Yemen. This is supported by the degree of isolation characterizing this area of Arabia.
The finding of these two Afrotropical ant species groups in this area further supports the claim that Al Bahah region in southwestern Arabia biogeographically is Afrotropical [25,26] and has a distinct history from the rest of the Arabia.
By comparison of the descriptions of T. jizani Collingwood and T. yemene Collingwood & Agosti, it is apparent also that these two species may be synonymous with the widely distributed invasive species T.simillimum (Smith)and T. delagoense Forel, as the number of genae hairs overlap. We suspect that the records of T. khyarum and T. delagoense from Arabia are due to misidentifications but examination of the material mentioned by Collingwood & Agosti [19], and comparison with appropriate type-material will be required.
Finally, the total of nineteen species of Tetramorium recorded from Arabia is a relative modest number considering the vastness of the region and the diversity of habitats. We expect additional collecting will reveal additional species.