Tetramorium hobbit 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 : 31-35

Tetramorium hobbit Hita Garcia & Fisher sp. n. Figs 10A, 12A, 17, 62

Type material.

Holotype, pinned worker, MADAGASCAR, Toliara, Parc National de Tsimanampetsotsa, Forêt de Bemanateza, 20.7 km 81° E Efoetse, 23.0 km 131° SE Beheloka, 23.99222°S, 43.88067°E, 90 m, spiny forest/thicket, sifted litter (leaf mold, rotten wood), collection code BLF06254, 22.-26.III.2002 (B.L. Fisher et al.) (CAS: CASENT0019207). Paratypes, 2 pinned workers with same data as holotype (CAS: CASENT0019210; CASENT0019227); 2 pinned workers with same data as holotype except collected from pitfall trap and collection code BLF06258 (CAS: CASENT0078055; MHNG: CASENT0078059); 5 pinned workers with same data as holotype except collected from ground nest and collection code BLF06270 (CAS: CASENT0445004; CASENT0445005); and 2 pinned workers with same data as holotype except sampled from ground and collection code BLF06337 (MCZ: CASENT0445502; CASENT0445520).

Non-type material.

MADAGASCAR: Fianarantsoa, Ampandravelo II Non Protected Area, 10.78 km NE Ranohira, 22.5392°S, 45.5155°E, 873 m, shrubland, 20.-22.II.2010 (A. Ravelomanana); Fianarantsoa, Ampotoampoto I National Parc, 8.02 km NW Ilakaka, 22.6283°S, 45.1886°E, 917 m, savannah woodland, 26.-28.II.2010 (A. Ravelomanana); Fianarantsoa, Ampotoampoto III National Parc, 7.91 km NW Ilakaka, 22.6294°S, 45.189°E, 919 m, savannah woodland, 27.-28.II.2010 (A. Ravelomanana); Fianarantsoa, Ampotoampoto IV National Parc, 7.83 km NW Ilakaka, 22.6294°S, 45.1912°E, 923 m, savannah woodland, 27.-28.II.2010 (A. Ravelomanana); Toliara, Parc National d’Andohahela, Forêt de Manantalinjo, 33.6 km 63° ENE Amboasary, 7.6 km 99° E Hazofotsy, 24.8169°S, 46.61°E, 150 m, spiny forest/thicket, 12.-16.I.2002 (B.L. Fisher et al.); Toliara, Forêt de Beroboka, 5.9 km 131° SE Ankidranoka, 22.2331°S, 43.3663°E, 80 m, tropical dry forest, 12.-16.III.2002 (B.L. Fisher et al.); Toliara, Parc National de Kirindy Mite, 16.3 km 127° SE Belo sur Mer, 20.7953°S, 44.147°E, 80 m, tropical dry forest, 6.-10.III.2002 (B.L. Fisher et al.); Toliara, Makay Mts., 21.3411°S, 45.1805°E, 500 m, barren rock with sparse vegetation, burned grass, 28.XI.2010 (B.L. Fisher et al.); Toliara, Parc National de Tsimanampetsotsa, Forêt de Bemanateza, 20.7 km 81° E Efoetse, 23.0 km 131° SE Beheloka, 23.99222°S, 43.88067°E, 90 m, spiny forest/thicket, 22.-26.III.2002 (B.L. Fisher et al.).

Diagnosis.

Tetramorium hobbit is easily recognisable within the Tetramorium plesiarum species group due to its massively developed petiolar node and very conspicuous reticulate-punctate ground sculpture on head and mesosoma.

Worker measurements

(N=12). HL 0.79-0.88 (0.84); HW 0.80-0.88 (0.85); SL 0.52-0.58 (0.55); EL 0.16-0.20 (0.18); PH 0.42-0.53 (0.47); PW 0.63-0.72 (0.69); WL 0.96-1.11 (1.04); PSL 0.16-0.25 (0.20); PTL 0.28-0.31 (0.30); PTH 0.40-0.46 (0.44); PTW 0.38-0.45 (0.41); PPL 0.24-0.30 (0.27); PPH 0.39-0.45 (0.43); PPW 0.45-0.54 (0.51); CI 100-102 (101); SI 64-67 (65); OI 19-22 (21); DMI 63-72 (66); LMI 43-50 (46); PSLI 18-29 (23); PeNI 57-66 (60); LPeI 63-71 (68); DPeI 133-148 (140); PpNI 69-76 (74); LPpI 60-67 (63); DPpI 175-200 (188); PPI 116-126 (122).

Worker description.

Head as long as wide to weakly longer than wide (CI 100-102); posterior head margin weakly concave. Anterior clypeal margin with distinct median impression. Frontal carinae strongly developed and forming dorsal margin of very well-developed antennal scrobes, scrobes moderately to very deep and with clearly defined margins all around; median scrobal carina very well developed and distinctly surpassing posterior eye level, usually approaching posterior scrobe margin. Antennal scapes short, not reaching posterior head margin (SI 64-67). Eyes relatively small to moderate (OI 19-22). Mesosomal outline in profile conspicuously convex, rounded and often very high (LMI 43-50), moderately marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent. Propodeal spines either short and elongate-triangular or long and spinose (PSLI 18-29; material from Andohahela and Tsimanampetsotsa with PSLI of 28-29; material from other localities PSLI 18-20), spines always with broad base and acute tip; propodeal lobes well developed, elongate- triangular, and acute, always shorter than propodeal spines. Petiolar node massively developed, very large, in profile high, rectangular, blocky nodiform with well defined antero- and posterodorsal margins, between 1.4 to 1.6 times higher than long (LPeI 63-71), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about the same height, petiolar dorsum flat to weakly convex; node in dorsal view around 1.3 to 1.5 times wider than long (DPeI 133-148), in dorsal view pronotum around 1.5 to 1.7 times wider than petiolar node (PeNI 57-66). Postpetiole in profile subglobular to anteroposteriorly compressed, approximately 1.5 to 1.7 times higher than long (LPpI 60-67); in dorsal view around 1.7 to 1.9 times wider than long (DPpI 175-200), pronotum around 1.3 to 1.4 times wider than postpetiole (PpNI 69-76). Petiole in profile much more voluminous than postpetiole, in dorsal view postpetiole only about 1.1 to 1.3 times wider than petiolar node (PPI 116-126). Mandibles usually finely longitudinally rugulose, fairly smooth and shiny, sometimes unsculptured; clypeus longitudinally rugose, usually with five to seven very distinct and strong rugae, median ruga better developed than remainder, rugae usually without cross-meshes; cephalic dorsum between frontal carinae with 11 to 13 longitudinal rugae, rugae running from posterior clypeal margin to posterior head margin, often interrupted or with cross-meshes, especially posteriorly; scrobal area mostly unsculptured, only with ground sculpture; lateral head mainly reticulate-rugose. Mesosoma laterally reticulate-rugose to irregularly longitudinally rugose, dorsally mostly longitudinally rugose. Forecoxae unsculptured, smooth, and shining, often with weak traces of ground sculpture. In profile, basal half of petiolar node mostly unsculptured, upper half distinctly reticulate-rugose, dorsum of node distinctly reticulate-rugose; sculpture on postpetiole much weaker, laterally and dorsally only weakly rugulose. Gaster usually unsculptured, smooth and shining, sometimes with weak punctate ground sculpture at base of tergite. Ground sculpture on head, mesosoma, and petiolar node very conspicuous, usually strongly reticulate-punctate; ground sculpture on postpetiole and gaster usually much weaker but present, though sometimes absent. Whole body with very abundant, long, and fine standing hairs; first gastral tergite with abundant, long, erect hairs and much scarcer, shorter, decumbent to subdecumbent hairs. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with decumbent to suberect hairs. Body reddish to dark brown, head and gaster usually darker than rest of body.

Etymology.

This very hairy new species is named after the fictional people from J.R.R. Tolkien’s novels "The Hobbit" and "The Lord of the Rings". The species epithet is an arbitrary combination of letters, thus invariant.

Distribution and biology.

The distribution of Tetramorium hobbit is approximately restricted to the southern third of the island of Madagascar (Fig. 62). In the south, the distribution range encompasses the type locality Tsimanampetsotsa in the west and Andohahela in the east, while the Makay Mountains and Isalo mark the northernmost known localities. Interestingly, the population in Andohahela seems to be slightly isolated from the other, more western localities. However, we consider this to be more of a sampling artifact. Like the remainder of the species group, Tetramorium hobbit prefers arid habitats, such as tropical dry forests, spiny forests and thickets, savannah woodland, and barren rocks with little vegetation. It is found at elevations of 80 to 923 m. Tetramorium hobbit is likely a ground-active species since it was mainly collected from leaf litter extractions and pitfall traps.

Discussion.

Tetramorium hobbit is very unlikely misidentified with the other four species of the group. The massively enlarged petiolar node, in combination with the distinct reticulate-punctate ground sculpture on head and mesosoma, are not seen in any other group member. However, of all group members, Tetramorium mars seems morphologically closest to Tetramorium hobbit , especially on the basis of the blockier petiolar node shape seen in profile that both species share. However, in addition to the smaller petiolar node and the lack of reticulate-punctate ground sculpture on head and mesosoma, Tetramorium mars also has shorter antennal scapes (SI 58-62; DPeI 108-122) and a narrower petiolar node in dorsal view than Tetramorium hobbit (SI 64-67; DPeI 133-148). Tetramorium mars (HW 0.69-0.74; WL 0.83-0.96) is also smaller than Tetramorium hobbit (HW 0.80-0.88; WL 0.96-1.10)

One noticeable intraspecific variation can be observed within Tetramorium hobbit . There are two distinct groups with differently developed propodeal spines. The populations from the type localities Tsimanampetsotsa and Andohahela always have relatively long spines (PSLI of 28-29), which contrast with the much shorter spines seen in the material from in Beroboka, Kirindy, Isalo, and the Makay Mountains (PSLI 18 -20). This difference is very pronounced and constant in all of the examined material. However, since there is no other obvious morphological difference between the short-spined and the long-spined populations, we treat them as conspecific in this study.