Technomyrmex montaseri sp. n., a new ant species of the T. gibbosus-group from Oman (Hymenoptera, Formicidae) with a key to the Technomyrmex species of the Arabian Peninsula

Abstract Technomyrmex montaseri sp. n. is described and illustrated from Oman based on the worker caste collected in Bani Sur. It belongs to the Technomyrmex gibbosus-group, with closest resemblance to Technomyrmex vexatus (Santschi, 1919) and Technomyrmex gibbosus W. M. Wheeler, 1906. A key to the Arabian Technomyrmex is given.


Introduction
The ant genus Technomyrmex Mayr, 1872 comprises one of the largest and most diverse ant genera in the subfamily Dolichoderinae. Ninety species are known world wide, distributed throughout the tropical and subtropical zones; most species occur in the Oriental-Malesian (sensu Bolton 2007) and Afrotropical regions. The workers of the genus Technomyrmex are clearly diagnosed by the following characters (as defined by Bolton 2007). Masticatory margin of mandible multidentate, with 12-14 teeth. Palp formula 6,4 in the vast majority of species. Median portion of anterior clypeal margin transverse to very deeply incised. Antennae 12-segmented, without a club. Metanotal groove present. Propodeum unarmed, its dorsum-declivity junction broadly rounded to distinctly angular. Petiole extremely reduced, forming a low narrow segment without a node or scale. Petiole concealed in dorsal view when gaster is in line with mesosoma, overhung by the anteriorly projecting first gastral tergite. A groove is present in the anterior face of the first gastral tergite that accommodates the petiole. Gaster with five visible tergites and sternites, the pygidium small.
The Technomyrmex of the Arabian peninsula have been studied fragmentarily and probably many species remain undiscovered. This paper continues our contributions towards the knowledge of Arabian Technomyrmex. The first contribution was by Collingwood (1985). He reported T. albipes (Smith, 1862) and T. sp. A, which is almost certainly a member of the genus Tapinoma ( fig. 14 Collingwood and Agosti (1996) followed this by recording the same species and adding T. bruneipes Forel, 1895 from Yemen and other localities in Saudi Arabia. An additional record of T. sp. B was from Oman and Yemen. Bolton (2007) reverted T. bruneipes to the status of a junior synonym of T. albipes. More recently, Sharaf (2009) described a further member of the T. albipes-group, T. briani from Wadi Abha, Asir, Saudi Arabia. With the revision of Technomyrmex by Bolton (2007), we have been able to confirm Technomyrmex sp. B as a new species.
The T. gibbosus group (Bolton 2007) is distinguished from other Technomyrmex species-groups by the combination of the following characters. The anterior clypeal margin has only the weakest of median impressions and setae are entirely lacking from the head behind the clypeus, the mesosoma including the propodeal declivity, and gastral tergites 1-3. With the mesosoma in profile the pronotum and mesonotum form separate curved surfaces and the mesonotum is distinctly convex. Palp formula 6,4. Bolton gave only two species in the group, T. gibbosus from Japan and T. vexatus from Morocco and recently recorded from the Iberian Peninsula (Gibraltar) (Guillem and Bensusan 2008). The latter and T. setosus are the only species he listed from the "Western Palaearctic", a geographical area in which he includes Saudi Arabia and Yemen. Bolton was unable to locate the Collingwood type specimens and noted those he examined from the Liverpool Museum matched the Collingwood description but not the drawing.
In this paper Technomyrmex montaseri new species is described from Oman.

Material and methods
Measurements and indices were taken according to Bolton (2007).

Measurements:
TL Total Length. The total outstretched length of the ant from the mandibular apex to the gastral apex.

HL
Head Length. The length of the head capsule excluding the mandibles; measured in full-face view in a straight line from the mid-point of the anterior clypeal margin to the mid-point of the posterior margin. In species where one or both of these margins is concave the measurement is taken from the mid-point of a transverse line that spans the apices of the projecting portions. HW Head width. The maximum width of the head behind the eyes, measured in full-face view.

SL
Scape length. The maximum straight-line length of the scape, excluding the basal constriction or neck that occurs just distal of the condylar bulb.

PW
Pronotal width. The maximum width of the pronotum in dorsal view.

WL
Weberś length of Mesosoma. The diagonal length of the mesosoma in profile, from the anterior most point of the pronotum to the posterior basal angle of the metapleuron.
All measurements are expressed in millimeters.  The photographic images were taken using a digital camera attached to a stereomicroscope. The microscope was equipped with a Z-Stepper to enable the generation of usually 30 images in different focus layers from which a montage image was computed using Auto-Montage Pro.  (Collingwood 1985); Oman, Bani Sur (as the holotype and paratype) and Eastern Sands, iii.1986, all W. Büttiker; also, Yemen, Al-Hajjarah, 14.iii.1992, A van Harten (Collingwood and Agosti 1996).

Technomyrmex montaseri
Diagnosis. This new species is characterized by the combination of the following characters: Head, mesosoma and all gastral tergites without setae. Anterior clypeal margin with a shallow but distinct median concavity. In full-face view the occipital margin and the sides of the head are convex.
Worker description. Dorsum of head behind clypeus entirely lacks setae. Anterior clypeal margin with a shallow but distinct median concavity. In full-face view the posterior margin of the head and the sides clearly convex. Eyes of moderate size, located in front of the midlength and their outer margins just failing to break the outline of the sides. Sculpture of head a very weak, superficial and effaced microreticulum. Dorsum of mesosoma and propodeal declivity entirely lack setae. With mesosoma in profile the mesonotal dorsal outline consists of an anterior section that is short and flat to feebly convex; posterior to this the surface curves broadly and evenly into a larger, more steeply sloped posterior section that descends to the narrow mesonotal groove. Propodeum in profile with a short convex dorsal surface that rounds evenly into the declivity, the two surfaces not separating by an angle. Sculpture reduced and superficial on dorsal mesosoma and all gastral tergites; the latter without pubescence. All gastral tergites, scapes and tibiae without setae. Colour uniform yellow.

Key to the Arabian species of the genus Technomyrmex
We include T. vexatus in the key of the Arabian Technomyrmex as it is the only other West Palaearctic species of its group and may well be discovered in other areas, beside Morocco and Gibraltar where it now is known.

Affinities
This new species is a member of the Technomyrmex gibbosus-group as defined by Bolton (2007) and cannot be identified with any of the Technomyrmex species in his extensive review. T. montaseri appears taxonomically closest to T. vexatus (Santschi, 1919), known only from Morocco and Gibraltar, and T. gibbosus W. M. Wheeler, 1906, which was described from Japan and otherwise know only from North Korea (Radchenko 2005). All three species are completely without setae on the head behind the clypeus, or on the mesosoma including the propodeal declivity. With the mesosoma in profile the mesonotal dorsal outline is convex, consisting of a shallowly convex anterior section that curves broadly and evenly into a more sloping shallow convexity that descends to the metanotal groove. The propodeum in profile has a short convex dorsal surface that rounds into the declivity. Scapes and tibiae without setae. T. montaseri may be closer to T. vexatus, but differs in colour which is uniform yellow while it is brown in T. vexatus. T. montaseri also is consistently smaller, TL 2.8-2.9 versus TL 3.-3.4. T. montaseri has the eyes located in front of the midlength of the head, whereas in T. vexatus they are situated close to the midlength; thus the eye position index is larger, EPI 80-125, versus EPI 68-76. T. montaseri has a higher scape index, SI 97-109 versus SI 90-94; has a smaller Weber's length of mesosoma, WL 0.65-0.80 versus WL 0.90-0.96, and has a clearly convex occipital margin, that is very shallowly impressed in T. vexatus. Additionally, T. montaseri has completely bare gastral tergites, while in T. vexatus gastral tergites 1-3 are without setae but the fourth has 2-3 pairs. T. montaseri lacks pubescence on the first gastral tergite, whereas short and sparse pubescence is present in T. vexatus. T. montaseri and T. gibbosus are similar in most measurements but the scape length in T. montaseri is consistently larger, SL 0.58-0.62 versus SL 0.50-0.54. T. montaseri has a higher cephalic index, CI 95-97 versus SI 86-91, a higher scape index, SI 97-109 versus SI 85-93; a significantly higher eye position index, EPI 80-125 versus EPI 50-58; and a smaller Weber's length of mesosoma, WL 0.65-0.80 versus WL 0.76-0.84. In T. montaseri the posterior margin of the head and the sides are broadly convex, whereas in T. gibbosus the posterior margin of the head has a median indentation and the sides are only shallowly convex. In T. montaseri all gastral tergites are bare whereas in T. gibbosus gastral tergites 1-3 lack setae but the fourth tergite has 1-2 pairs. T. montaseri is yellow while T. gibbosus has a medium to dark brown mesosoma, often with a reddish tint; the gasters are about the same medium to dark brown, with the legs dull yellow to yellowish brown. Moreover, T. gibbosus has very fine, short, appressed pubescence present on the first and second gastral tergites. This pubescence is somewhat more dense in T. gibbosus than T. vexatus.

Technomyrmex gibbosus-group
As previously known, the Technomyrmex gibbosus-group contains a pair of geographically widely separated species, T. vexatus from Morocco and Gibraltar and T. gibbosus from North Korea and Japan. The distribution of T. montaseri (Oman, Yemen and Saudi Arabia) fills a gap in that distribution. Bolton (2007: 41, 82) speculated that vexatus and gibbosus might share an intermediate common ancestor, or could be remnants of a fairly distinctive species group that once extended across the width of the southern Palaearctic. Alternatively each might have acquired the shared characters by convergence from unrelated ancestors. With our specimens of this new species we feel able to support the idea of the intermediate common ancestor from Western or Central Asia.
Five species of the genus Technomyrmex are known now from the Arabian Peninsula. If one takes into account the large area and its location between the Palaearctic, Oriental and Afrotropical regions, this figure is very low. Therefore, one would expect to find many more species of this genus and from the gibbosus-group with more intensive collecting efforts. senior author greatly acknowledges his wife Ms. Amal M. El-Saadany, his mother Eglal H. El-Saadany, and his friends Dr Fareed Krupp (Fauna of Arabia), Prof. Hoda Farid (Ain Shams University, Cairo), Col. Hisham El-Hennawy (Spider taxonomist) and Dr Mahmoud Eldera'a for their continuous encouragement.