Tetramorium bressleri

Tetramorium bressleri was mainly sampled by pitfall trapping and litter sifting, suggesting a ground-active life style. It has a wide range in Madagascar.

Identification
A member of the Tetramorium plesiarum species group. A member of the Tetramorium plesiarum species group. Hita Garcia and Fisher (2014) - Tetramorium bressleri can be recognised by the following combination of characters: larger species (HW 0.80–1.00; WL 0.92–1.15); eyes relatively small (OI 18–19); petiolar node high nodiform, not blocky and massively enlarged, anterodorsal and posterodorsal margins at about the same height and equally marginate, anterodorsal margin not protruding anteriorly nor very sharply angled; petiolar node in profile relatively high and thin, between 1.6 to 1.8 times higher than long (LPeI 56–61), in dorsal view between 1.3 to 1.5 times wider than long (DPeI 135–145); gaster never extremely enlarged and swollen; head and mesosoma without strongly developed and conspicuous reticulate-punctate ground sculpture; usually sculpture on the mesopleuron and lateral propodeum mostly absent; basal half of first gastral tergite not strongly reticulate-rugose, only base of tergite weakly sculptured; pilosity on first gastral tergite mostly erect.

Tetramorium bressleri is not likely to be confused with Tetramorium gollum, Tetramorium hobbit, or Tetramorium mars, whereas differentiating between T. bressleri and Tetramorium plesiarum can be challenging at first glance. Tetramorium bressleri lacks the enlarged gaster and strong reticulate-rugose sculpture on the basal half of the first gastral tergite seen in T. gollum, nor does it have the blocky petiolar node shape of T. mars or the massively enlarged petiolar node of T. hobbit. The separation from T. plesiarum requires more attention and caution. The main and obvious difference is body size. Tetramorium bressleri is usually a much larger species (HW 0.80–1.00; WL 0.92–1.15) than T. plesiarum (HW 0.80–1.00; WL 0.92–1.15). There is some overlap, but this is mainly due to a few very small specimens of T. bressleri and one very large specimen of T. plesiarum. Otherwise, both species fall neatly into their respective size ranges. However, body size alone should not be used as a primary diagnostic character, and in this case, we provide more evidence for their heterospecificity. The eyes of T. plesiarum (OI 21–23) are larger than in T. bressleri (OI 18–19), although this is often difficult to assess without measuring. In addition, both can be separated by the sculpture on the mesopleuron and lateral propodeum; this sculpture is usually mostly absent in T. bressleri, making the area appear very smooth and shiny, while it is usually longitudinally rugose with reticulate-punctate ground sculpture in T. plesiarum. The sculpture on the sides of the petiolar node varies too, since it is much more reticulate-punctate and matte in T. plesiarum than in T. bressleri, in which the weak reticulate-punctate ground sculpture looks faintly matte but still relatively smooth and shiny. The shape of the petiolar node in profile is an additional useful character. In T. plesiarum the anterodorsal margin of the node protrudes anteriorly and is a bit more marginate than the more rounded posterodorsal margin, while in T. bressleri both margins are usually equally marginate and the anterodorsal margin does not protrude anteriorly at all.

Considering how common and abundant T. bressleri is in western Madagascar, it is interesting that it shows very little intraspecific variation and remains very stable in its morphology.

Key to Tetramorium plesiarum-group species

Distribution
Hita Garcia and Fisher (2014) - Tetramorium bressleri is by far the most common and abundant species of the T. plesiarum group. The material available was sampled in many localities and includes more than 500 mounted specimens with many more in alcohol. The distribution ranges of all group members strongly overlap, but the range of T. bressleri is by far the largest; this species is known from many more localities than the other four. The southernmost localities are Andohahela, Beza Mahafaly, and Fiherenana, and from there the distribution ranges north through much of western Madagascar up to the northernmost known locality Anabohazo. The eastern limit of the range goes in an almost straight line north from Andohahela through Mampiarika, Ambohitantely, and Ambohimanga to Anabohazo.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Habitat
The new species prefers arid habitats such as tropical dry forests, tropical dry forests on tsingy, gallery forests, spiny deciduous forests, savannah woodland, Uapaca woodland, and spiny thickets. The elevational range of the species is a relatively broad one, ranging from 10 to 1550 m, but most of the material was collected at low elevations (ca. 420 m on average).

Nomenclature

 *  bressleri. Tetramorium bressleri Hita Garcia & Fisher, 2014: 33, figs. 10E, 11C, 12C, 13C, 14B, 15, 62 (w.) MADAGASCAR.

Worker
(N=12). HL 0.81–1.00 (0.94); HW 0.80–1.00 (0.94); SL 0.51–0.64 (0.60); EL 0.15–0.19 (0.18); PH 0.42–0.53 (0.48); PW 0.57–0.73 (0.68); WL 0.92–1.15 (1.07); PSL 0.24–0.32 (0.27); PTL 0.20–0.26 (0.23); PTH 0.35–0.42 (0.40); PTW 0.28–0.36 (0.32); PPL 0.23–0.30 (0.27); PPH 0.32–0.41 (0.38); PPW 0.35–0.45 (0.42); CI 98–102 (100); SI 62–65 (64); OI 18–19 (19); DMI 61–66 (64); LMI 43–47 (45); PSLI 26–32 (28); PeNI 45–49 (47); LPeI 56–61 (58); DPeI 135–145 (138); PpNI 59–63 (61); LPpI 70–75 (73); DPpI 150–158 (152); PPI 125–134 (130).

Head more or less as long as broad (CI 98–102); 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 ending halfway between posterior eye margin and posterior scrobe margin. Antennal scapes short, not reaching posterior head margin (SI 62–65). Eyes relatively small (OI 18–19). Mesosomal outline in profile weakly to moderately convex, rounded and high (LMI 43–47), moderately to strongly marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent. Propodeal spines elongate-triangular to spinose, long, and acute (PSLI 26–32), propodeal lobes short, triangular, and acute, always much shorter than propodeal spines. Petiolar node in profile high, rectangular nodiform with well defined antero- and posterodorsal margins, between 1.6 to 1.8 times higher than long (LPeI 56–61), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about the same height, petiolar dorsum flat to weakly convex, anterodorsal margin not protruding anteriorly; node in dorsal view between 1.3 to 1.5 times wider than long (DPeI 135–145), in dorsal view pronotum between 2.0 to 2.2 times wider than petiolar node (PeNI 45–49). Postpetiole in profile subglobular and weakly anteroposteriorly compressed, approximately 1.3 to 1.4 times higher than long (LPpI 70–75); in dorsal view around 1.5 to 1.6 times wider than long (DPpI 150–158), pronotum between 1.6 to 1.7 times wider than postpetiole (PpNI 59–63). Postpetiole in profile appearing slightly less voluminous than petiolar node, postpetiole in dorsal view between 1.2 to 1.4 times wider than petiolar node (PPI 125–134). Mandibles variably sculptured, either unsculptured, smooth, and shining, or partly or fully finely rugulose; clypeus longitudinally rugose/rugulose, with five to eight distinct rugae, median ruga always distinct, lateral rugae often weaker and sometimes interrupted; cephalic dorsum between frontal carinae with ten to thirteen longitudinal rugae, rugae running from posterior clypeal margin to posterior head margin, rarely interrupted or with cross-meshes; scrobal area mostly unsculptured, smooth and shiny; lateral head mainly longitudinally rugose. Ground sculpture on head usually weak to absent. Dorsum of mesosoma mostly longitudinally rugose without any distinct ground sculpture, spaces between rugae smooth and shining; lateral pronotum irregularly longitudinally rugose, often with weak to moderate punctate ground sculpture, mesopleuron and lateral propodeum usually with very little sculpture, few irregular rugae/rugulae and no ground sculpture. Forecoxae often with weak ground sculpture, but generally very smooth and shining. Petiolar node laterally with conspicuous but relatively weak reticulate-punctate ground sculpture only, appearing weakly matte but still relatively smooth and shiny; dorsum of node medially almost unsculptured, smooth, and shiny, surrounding areas rugulose, ground sculpture on petiolar dorsum neglectable. Postpetiole laterally and dorsally weakly to moderately rugose/rugulose and with conspicuous, moderate reticulate-punctate ground sculpture, appearing relatively matte; base of first gastral tergite usually weakly punctate and/or costulate and/or shagreened, remainder of tergite unsculptured, smooth, and shining. Whole body with 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 usually of uniform brown, appendages often lighter.

Type Material
Holotype, pinned worker, MADAGASCAR, Mahajanga, Parc National de Namoroka, 9.8 km 300° WNW Vilanandro, 16.46667°S, 45.35°E, 140 m, tropical dry forest, sifted litter (leaf mold, rotten wood), collection code BLF06446, 4.–8. XI.2002 (B.L. Fisher et al.) (: CASENT0035677). Paratypes, 27 pinned workers with same data as holotype (: CASENT0035669; CAS: CASENT0035636; CASENT0035640; CASENT0035642; CASENT0035647; CASENT0035648; CASENT0035649; CASENT0035652; CASENT0035653; CASENT0035654; CASENT0035656; CASENT0035658; CASENT0035660; CASENT0035662; CASENT0035666; CASENT0035667; CASENT0035670; CASENT0035674; CASENT0035675; CASENT0035678; CASENT0035681; CASENT0035686; CASENT0035687; CASENT0035689; CASENT0035694; CASENT0035703; : CASENT0035646).

Etymology
The name of the new species is a patronym dedicated to Dr. Barry Lee Bressler, retired physicist, former adjunct professor of physics at Virginia Polytechnic Institute and State University, and amateur naturalist, in recognition of his interest in myrmecology and his support of ant taxonomy.