Tetramorium obiwan Hita Garcia & Fisher

Hita Garcia, Francisco & Fisher, Brian L., 2014, The hyper-diverse ant genus Tetramorium Mayr (Hymenoptera, Formicidae) in the Malagasy region taxonomic revision of the T. naganum, T. plesiarum, T. schaufussii, and T. severini species groups, ZooKeys 413, pp. 1-170 : 92-95

Tetramorium obiwan Hita Garcia & Fisher sp. n. Figs 20D, 43B, 44A, 53, 65

Type material.

Holotype, pinned worker, MADAGASCAR, Toliara, Parc National d’Andohahela, Col du Sedro, 3.8 km 113° ESE Mahamavo, 37.6 km 341° NNW Tolagnaro, 24.76389°S, 46.75167°E, 900 m, montane rainforest, beating low vegetation, collection code BLF05014, 21.-25.I.2002 (B.L. Fisher et al.) (CAS: CASENT0447245). Paratypes, three pinned workers with same data as holotype (CAS: CASENT0447199; CASENT0447207; MCZ: CASENT0447237); eight pinned workers with same data as holotype except sampled from canopy moss and leaf litter and collection codes BLF05036 and BLF05136 (CAS: CASENT0451274; CASENT0451275; CASENT0451276; CASENT0455961); four pinned workers with same data as holotype except sampled from sifted litter and collection code BLF05010 (BMNH: CASENT0484542; CAS: CASENT0484425; CASENT0484536; CASENT0484554).

Non-type material.

MADAGASCAR: Antananarivo, 3 km 41° NE Andranomay, 11.5 km 147° SSE Anjozorobe, 18.47333°S, 47.96°E, 1300 m, montane rainforest, 5.-13.XII.2000 (B.L. Fisher et al.); Antsiranana, Rés. Anjanaharibe-Sud, 9.2 km WSW Befingotra, 14.75°S, 49.46667°E, 1260 m, montane rainforest, 11.XI.1994 (B.L. Fisher); Antsiranana, Betaolana Forest, along Bekona River, 14.52996°S, 49.44039°E, 880 m, rainforest, 4.III.2009 (B.L. Fisher et al.); Fianarantsoa, Rés. Andringitra, 40 km S Ambalavao, 22.21667°S, 46.96667°E, 1225 m, montane rainforest, 19.X.1993 (B.L. Fisher); Fianarantsoa, Parc National Befotaka-Midongy, Papango 28.5 km S Midongy-Sud, Mount Papango, 23.84083°S, 46.9575°E, 1250 m, montane rainforest, 17.-18.XI.2006 (B.L. Fisher et al.); Fianarantsoa, Ranomafana National Park, radio tower, 21.25083°S, 47.40717°E, 1130 m, forest edge, mixed tropical forest, open area, 4.-21.I.2002 (M. Irwin & R. Harin’Hala); Fianarantsoa, Parc National de Ranomafana, Vatoharanana River, 4.1 km 231° SW Ranomafana, 21.29°S, 47.43333°E, 1100 m, montane rainforest, 27.-31.III.2003 (B.L. Fisher et al.); Fianarantsoa, Parc National de Ranomafana, Sahamalaotra River, 6.6 km 310° NW Ranomafana, 21.23667°S, 47.39667°E, 1150 m, montane rainforest, 31.III.2003 (B.L. Fisher et al.); Toamasina, 6 km ESE Andasibe (=Perinet), 18.95°S, 48.46667°E, 900 m, rainforest, 17.XI.1990 (P.S. Ward); Toamasina, Corridor Forestier Analamay-Mantadia, Ambatoharanana, 18.80388°S, 48.40506°E, 1013 m, rainforest, 12.-19.2012 (B.L. Fisher et al.); Toamasina, Corridor Forestier Analamay-Mantadia, Ambatoharanana, 18.79956°S, 48.4028°E, 1058 m, rainforest, 12.-19.2012 (B.L. Fisher et al.); Toamasina, Corridor Forestier Analamay-Mantadia, Ambatoharanana, 18.80398°S, 48.40358°E, 1064 m, rainforest, 12.-19.2012 (B.L. Fisher et al.); Toamasina, Ankerana, 18.4017°S, 48.80605°E, 1035 m, montane forest, 26.I.2012 (B.L. Fisher et al.); Toliara, Parc National d’Andohahela, Col du Sedro, 3.8 km 113° ESE Mahamavo, 37.6 km 341° NNW Tolagnaro, 24.76389°S, 46.75167°E, 900 m, montane rainforest, 21.-25.I.2002 (B.L. Fisher et al.); Toliara, Forêt Ivohibe 55.6 km N Tolagnaro, 24.56167°S, 47.20017°E, 650 m, rainforest, 4.XII.2006 (B.L. Fisher et al.).

Diagnosis.

The following character combination distinguishes Tetramorium obiwan from the other species of the Tetramorium schaufussii complex: relatively larger species (HW 0.71-0.84; WL 1.00-1.20); frontal carinae moderately to very well developed, diverging posteriorly, becoming weaker halfway between posterior eye margin and posterior head margin, and ending at or shortly before posterior head margin; antennal scapes short to moderate (SI 77-82); eyes relatively large (OI 25-27); propodeal spines short, triangular to elongate-triangular, and acute (PSLI 10-16), propodeal lobes short, triangular, and blunt or acute, always much shorter than propodeal spines, spines and lobes never strongly inclined towards each other; petiolar node high rounded nodiform, in profile around 1.6 to 1.9 times higher than long (LPeI 54-64), and in dorsal view around 1.1 to 1.3 times wider than long (DPeI 109-129); waist segments usually without any standing hairs, sometimes one pair of long, standing hairs present on petiole and/or postpetiole.

Worker measurements

(N=15). HL 0.78-0.93 (0.86); HW 0.71-0.84 (0.78); SL 0.56-0.69 (0.62); EL 0.18-0.22 (0.20); PH 0.36-0.44 (0.41); PW 0.50-0.60 (0.57); WL 1.00-1.20 (1.10); PSL 0.08-0.14 (0.12); PTL 0.15-0.20 (0.18); PTH 0.27-0.33 (0.30); PTW 0.18-0.23 (0.21); PPL 0.19-0.24 (0.23); PPH 0.27-0.32 (0.31); PPW 0.25-0.32 (0.29); CI 89-92 (90); SI 77-82 (80); OI 25-27 (26); DMI 50-53 (51); LMI 36-38 (37); PSLI 10-16 (14); PeNI 35-39 (36); LPeI 54-64 (58); DPeI 109-129 (117); PpNI 50-53 (51); LPpI 70-77 (74); DPpI 124-135 (129); PPI 135-148 (142).

Worker description.

Head clearly longer than wide (89-92); posterior head margin weakly concave. Anterior clypeal margin with distinct median impression. Frontal carinae moderately to very well developed, diverging posteriorly, becoming weaker halfway between posterior eye margin and posterior head margin, and ending at or shortly before posterior head margin. Antennal scrobes very weak to absent, shallow, and without any posterior and ventral margins. Antennal scapes short to moderate, not reaching posterior head margin (SI 77-82). Eyes relatively large (OI 25-27). Mesosomal outline in profile relatively flat to weakly convex, comparatively low and elongate (LMI 36-38), weakly to moderately marginate from lateral to dorsal mesosoma; promesonotal suture absent; metanotal groove either weakly developed or absent. Propodeal spines short, triangular to elongate-triangular, and acute (PSLI 10-16), propodeal lobes short, triangular, and blunt or acute, always much shorter than propodeal spines, spines and lobes not strongly inclined towards each other. Petiolar node in profile high rounded nodiform, around 1.6 to 1.9 times higher than long (LPeI 54-64), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about same height and well rounded, petiolar dorsum weakly to moderately convex; node in dorsal view around 1.1 to 1.3 times wider than long (DPeI 109-129); in dorsal view pronotum around 2.6 to 2.9 times wider than petiolar node (PeNI 35-39). Postpetiole in profile globular, around 1.3 to 1.4 times higher than long (LPpI 70-77); in dorsal view around 1.2 to 1.4 times wider than long (DPpI 124-135); in dorsal view pronotum around 1.9 to 2.0 times wider than postpetiole (PpNI 50-53). Postpetiole in profile appearing more or less of same volume as petiolar node, postpetiole in dorsal view between 1.3 to 1.5 times wider than petiolar node (PPI 135-148). Mandibles unsculptured, smooth, and shiny; clypeus weakly longitudinally rugulose with three to five, rarely more, rugulae, rugulae often interrupted or irregularly shaped, median area usually weakly sculptured without median rugula, median rugula sometimes partly and rarely fully developed; cephalic dorsum between frontal carinae longitudinally rugose/rugulose with seven to ten rugae/rugulae; rugae/rugulae running from posterior clypeal margin to posterior head margin, often interrupted, or with cross-meshes; scrobal area mostly unsculptured and laterally merging with surrounding reticulate-rugose to longitudinally rugose sculpture present on lateral head, sometimes head posterolaterally with very little sculpture, very smooth, and shining. Dorsum of mesosoma irregularly longitudinally rugose to reticulate-rugose, anterior pronotum especially reticulate-rugose; lateral mesosoma mostly irregularly longitudinally rugose with few unsculptured areas on lateral pronotum and/or katepisternum. Forecoxae mainly unsculptured, smooth, and shining. Waist segments and gaster unsculptured, smooth, and shining. Ground sculpture everywhere on body weak to absent. Dorsum of head with numerous pairs of long, fine, standing hairs; dorsum of mesosoma with seven to ten pairs, hairs present from anterior pronotum to posterior mesonotum, propodeum without standing pilosity; usually waist segments without any standing hairs, sometimes one pair of long, standing hairs present on petiole and/or postpetiole; first gastral tergite with very short, scarce, appressed pubescence in combination with few scarce, long, standing hairs. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae usually with appressed, rarely decumbent hairs. Head, mesosoma, waist segments and gaster uniformly light reddish, orange-brown to dark brown contrasting with lighter yellowish to light brown mandibles, antennae, and legs.

Etymology.

The name of the new species is inspired by a fictional character from George Lucas’ "Star Wars" Universe: the wise Jedi master Obi-Wan Kenobi. The species epithet is an arbitrary combination of letters, thus invariant.

Distribution and biology.

Tetramorium obiwan is widely but relatively patchily distributed throughout the rainforests and montane rainforests of eastern Madagascar (Fig. 65). Its known distribution encompasses nine localities, ranging from Andohahela in the southeast to Anjanaharibe-Sud in the northeast. A likely explanation for this patchy distribution record may be that Tetramorium obiwan lives in the vegetation and is consequently less often sampled by ground or leaf litter methods. The available collection data supports this, as Tetramorium obiwan was mainly collected by beating low vegetation or Malaise traps, and rarely from pitfall traps or leaf litter. If true, then Tetramorium obiwan is possibly much more widespread than currently known, and more collecting in lower vegetation will likely provide additional material of this species. Furthermore, Tetramorium obiwan seems to prefer higher elevations. It can be found from 675 to 1300 m, but most collections were from the upper altitudinal range limit.

Discussion.

Tetramorium obiwan is a fairly conspicuous member of the Tetramorium schaufussii complex, thus easily separable from the other species. As mentioned in the diagnosis above, its larger body size (HW 0.71-0.84; WL 1.00-1.20), strongly developed frontal carinae, relatively long antennal scapes (SI 77-82), relatively large eyes (OI 25-27), lack of median clypeal ruga, and (usually) lack of long, standing pilosity on the waist segments will separate it from the other species of the complex. Except for the relatively long antennal scapes, none of the characters listed is unique to Tetramorium obiwan , but the combination renders its identification very straightforward. Still, in a few cases it is possible to mistake Tetramorium obiwan at first glance for Tetramorium merina or Tetramorium nassonowii , which are also larger species. Nevertheless, Tetramorium merina has noticeably much weaker frontal carinae than Tetramorium obiwan . Tetramorium nassonowii is likely the species closest to Tetramorium obiwan but they differ significantly in the shape of the petiolar node. The node of Tetramorium obiwan is higher and broader, in profile around 1.6 to 1.9 times higher than long (LPeI 54-64), and in dorsal view around 1.1 to 1.3 times wider than long (DPeI 109-129), whereas the node of Tetramorium nassonowii is relatively long and low, in profile around 1.2 to 1.4 times higher than long (LPeI 72-81), and in dorsal view between 1.0 to 1.2 times longer than wide (DPeI 87-98). Despite being that distinctive in its own species complex, Tetramorium obiwan is comparatively similar to Tetramorium proximum from the Tetramorium cognatum species complex in that they are both large, reddish-brown species with relatively well-developed frontal carinae and a high rounded nodiform petiolar node. Nevertheless, the presence of long, standing pilosity on the first gastral tergite easily distinguishes Tetramorium obiwan from Tetramorium proximum that lacks any standing pilosity on the first gastral tergite.

Intraspecific variation in Tetramorium obiwan seems relatively low, especially considering that the species is fairly widely distributed.