Tetramorium schaufussii

An inhabitant of the leaf litter stratum.

Identification
A member of the Tetramorium schaufussii species complex of the Tetramorium schaufussii species group. Hita Garcia and Fisher (2014) - The following character combination separates T. schaufussii from the remaining species of the T. schaufussii complex: head much longer than wide (CI 86–90); antennal scapes short to very short (SI 66–73); eyes moderate to large (OI 24–28); frontal carinae usually moderately well developed, slightly diverging posteriorly, and typically fading out or merging with surrounding sculpture halfway between posterior eye and posterior head margin; propodeal spines usually short, triangular to elongate-triangular (PSLI 11–18), propodeal lobes short and triangular, usually of approximately same length as propodeal spines, sometimes lobes longer, rarely much shorter than spines, but spines and lobes never strongly inclined towards each other; petiolar node in profile high rounded nodiform, around 1.6 to 1.9 times higher than long (LPeI 52–63), in dorsal view between 1.1 to 1.4 times wider than long (DPeI 112–136); propodeum without standing pilosity; petiole and postpetiole with long, standing pilosity.

Tetramorium schaufussi is the most widespread, common, and abundant species of the T. schaufussi complex. Also, T. schaufussii co-occurs with all other members of the complex throughout its range. It can be well separated from most species, but its separation from a few morphologically close forms is more challenging. Due to its larger eyes (OI 24–28) T. schaufussii is very unlikely to be mistaken for Tetramorium pseudogladius (OI 20). Additionally, its petiolar node shape, which is always broader than long (DPeI 112–136), distinguishes it from Tetramorium nassonowii, which has a longer than broad node (DPeI 87–98). The species Tetramorium scutum, despite being morphologically relatively similar, has longer propodeal spines (PSLI 22–24) and the spines and propodeal lobes are strongly inclined towards each other. Tetramorium schaufussii always has shorter spines (PSLI 11–18) and the spines and lobes are never strongly inclined towards each other. Tetramorium rala and Tetramorium sikorae lack long, standing pilosity on the waist segments, separating them easily from T. schaufussii, but is should be noted that without consideration of the pilosity on the waist segments, T. sikorae is generally very similar to T. schaufussii. The difference, however, is very constant and both are usually found in sympatry, leading us to the decision to retain them as two species. Furthermore, most of the material of Tetramorium obiwan also lacks pilosity on the waist segments, distinguishing it from T. schaufussii, and, if pilosity is present, it is reduced to one pair on the petiole or postpetiole. Additionally, T. obiwan possesses longer antennal scapes (SI 77–82) and is much larger (HW 0.71–0.84; WL 1.00–1.20) than T. schaufussii (SI 66–73; HW 0.51–0.68; WL 0.70–0.93). In Tetramorium body size is usually not useful and often even misleading due to high intraspecific variation in many species (Hita Garcia et al. 2010; Hita Garcia and Fisher 2012a), but in the case of these two species we can confidently separate them by size.

The three species Tetramorium merina, Tetramorium monticola, and Tetramorium xanthogaster are often difficult to separate from T. schaufussii. The most important discriminating difference between these three and T. schaufussii is the shape of the head. In T. schaufussii the head is usually much longer and thinner (CI 86–90 vs. CI 91–95 in the other three species). Additionally, in T. schaufussii the clypeus almost always has a very distinct and unbroken median longitudinal ruga, whereas T. merina, T. monticola, and T. xanthogaster normally have the median area fully unsculptured without any median ruga/rugula at all, or the median ruga/rugula is present, but then it is usually interrupted, very irregularly shaped, or only present as traces. This character has to be treated with caution however, as there are a few specimens in T. merina, T. monticola, and T. xanthogaster, in which the median ruga/rugula is present. The delimitations of T. merina and T. schaufussii can be difficult, but in areas where they co-occur in the Central Highlands of Madagascar they can be easily separated by body size. In that area T. merina is always much larger in size and has shorter propodeal spines (PSLI 7–11) than T. schaufussii (PSLI 11–18).

It must be pointed out that T. schaufussii is highly variable, likely the most variable species of the T. schaufussii complex and the whole species group. There are several important characters varying significantly throughout the distribution range that need to be addressed here. The frontal carinae are moderately well developed in most of the material, but in one series from Mt. Anjanaharibe they are reduced and much weaker. As do several other species of the group, T. schaufussii possesses a comparatively variable petiolar node shape. It is generally high rounded nodiform with the anterodorsal and posterodorsal margins situated at about the same height and both equally rounded or angled. However, the node is often lower and thicker, and this variation can be seen within the same series or population. Sometimes the node also has a slightly higher and more angled anterodorsal margin in comparison to the posterodorsal margin, even though only weakly so. In addition, even though mostly stable, the propodeal spines do occasionally vary. They are usually short to very short (PSLI 11–15), but some specimens from Andranomay, Binara, and Marojejy have longer spines (PSLI 16–18). Also highly variable is colouration that also contains a geographic component. Most of the material from the southeast to the central east is much darker in colour, usually dark brown to almost black. The material from the north is very variable in colour ranging from very bright yellow (Mt. Anjanaharibe) to almost black (Marojejy), but usually constant on a local scale. Parallel to the colouration, there is also geographic variation observable in the sculpture on the forecoxae. Most of the darker material has the upper part of the forecoxae distinctly sculptured, whereas in most of the brighter material the forecoxae are completely unsculptured. However, this is not always the case, and thus not used for diagnostics.

The series from Mt. Anjanaharibe mentioned above also requires some comments. The specimens are much brighter in color, smaller in size, and have much weaker frontal carinae than the rest of the T. schaufussii material. These are not unlikely to turn out to be a distinct species, but for the moment we keep it as a smaller, brighter geographical variation of T. schaufussii.

Key to Tetramorium schaufussii  species complex workers

Distribution
Tetramorium schaufussii is broadly distributed throughout most of the humid forest zones from the southeast to the north of Madagascar. Surprisingly, T. schaufussii is also known from one very old collection event from the island of Reunion, but apart from that no modern collection exists from that island. Despite that we list Reunion as record for T. schaufussii we consider that record as problematic and highly questionable. (Hita Garcia and Fisher 2014)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Habitat
In Madagascar T. schaufussii is almost always found in rainforests or montane rainforests at elevations from 210 to 1875 m, even though most of the material was collected at elevations higher than 1000 m.

Nomenclature

 *  schaufussii. Tetramorium (Xiphomyrmex) schaufussii Forel, 1891b: 158 (w.) MADAGASCAR. Forel, 1892l: 263 (q.).

Worker
Hita Garcia and Fisher (2014) - (N=60). HL 0.59–0.76 (0.67); HW 0.51–0.68 (0.60); SL 0.36–0.50 (0.42); EL 0.14–0.19 (0.16); PH 0.26–0.35 (0.31); PW 0.38–0.50 (0.45); WL 0.70–0.93 (0.82); PSL 0.07–0.14 (0.10); PTL 0.12–0.17 (0.14); PTH 0.21–0.29 (0.25); PTW 0.15–0.20 (0.17); PPL 0.15–0.22 (0.18); PPH 0.20–0.28 (0.24); PPW 0.21–0.28 (0.25); CI 86–90 (88); SI 66–73 (71); OI 24–28 (26); DMI 52–59 (54); LMI 35–39 (37); PSLI 11–18 (15); PeNI 35–41 (39); LPeI 52–63 (57); DPeI 112–136 (124); PpNI 53–61 (56); LPpI 69–83 (75); DPpI 125–150 (137); PPI 131–153 (142).

Head much longer than wide (CI 86–90); posterior head margin weakly concave. Anterior clypeal margin with distinct median impression. Frontal carinae usually moderately well developed, slightly diverging posteriorly, and typically fading out or merging with surrounding sculpture halfway between posterior eye and posterior head margin. Antennal scrobes weak to absent, shallow and without clear and distinct posterior and ventral margins. Antennal scapes short to very short, not reaching posterior head margin (SI 66–73). Eyes moderate to large (OI 24–28). Mesosomal outline in profile flat to weakly convex, comparatively low and long (LMI 35–39), moderately marginate from lateral to dorsal mesosoma; promesonotal suture absent; metanotal groove either weakly developed or absent. Propodeal spines usually short, triangular to elongate-triangular (PSLI 11–18), propodeal lobes short and triangular, usually of approximately same length as propodeal spines, sometimes lobes longer, rarely much shorter than spines, but never strongly inclined towards each other. Petiolar node in profile high rounded nodiform, around 1.6 to 1.9 times higher than long (LPeI 52–63), anterior and posterior faces approximately parallel, usually anterodorsal and posterodorsal margins situated at about same height and equally angled, sometimes anterodorsal margin slightly higher, petiolar dorsum generally weakly convex, sometimes flat; node in dorsal view between 1.1 to 1.4 times wider than long (DPeI 112–136), in dorsal view pronotum between 2.4 to 2.8 times wider than petiolar node (PeNI 35–41). Postpetiole in profile globular, around 1.2 to 1.4 times higher than long (LPpI 69–83); in dorsal view between 1.2 to 1.5 times wider than long (DPpI 125–150), pronotum between 1.6 to 1.9 times wider than postpetiole (PpNI 53–61). Postpetiole in profile appearing more or less of similar volume as petiolar node, postpetiole in dorsal view around 1.3 to 1.5 times wider than petiolar node (PPI 131–153). Mandibles completely unsculptured, smooth, and shiny; clypeus longitudinally rugulose/rugose with three to six usually regularly shaped and unbroken rugulae/rugae, median ruga usually fully developed and distinct, very rarely broken, one or two lateral rugulae/rugae present on each side; cephalic dorsum between frontal carinae longitudinally rugulose/rugose with seven to ten rugae/rugulae, rugae/rugulae usually running from posterior clypeal margin to posterior head margin, often irregularly shaped, interrupted, or with cross-meshes; scrobal area partly unsculptured and merging with surrounding sculpture; lateral head reticulate-rugose to longitudinally rugose, often posteriorly mostly unsculptured. Ground sculpture on head usually well developed, moderately reticulate-punctate, especially on cephalic dorsum and scrobal area, sometimes ground sculpture much weaker, almost absent. Dorsum of mesosoma usually irregularly longitudinally rugose to reticulate-rugose, sometimes almost completely reticulate-rugose with few longitudinally rugose elements; lateral mesosoma mostly irregularly longitudinally rugose to reticulate-rugose, often lateral pronotum weaker sculptured to almost unsculptured. Ground sculpture on mesosoma variably developed, usually weakly to moderately punctate, sometimes very weak or absent. Forecoxae either unsculptured, smooth, and shining or with longitudinally rugulose or reticulate-rugose sculpture on upper half. Both waist segments and gaster fully unsculptured, smooth, and shining. Dorsum of head with several pairs of long, fine, standing hairs; mesosoma with six or more pairs on promesonotum, propodeum without standing pilosity; petiole usually with one or two and postpetiole with two to three pairs of long, standing hairs; first gastral tergite with short, moderately dense, appressed pubescence in combination with several scattered to numerous, long, standing hairs. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with appressed to decumbent hairs. Head, mesosoma, waist segments, and gaster uniformly light yellowish brown to very dark brown, almost black contrasting with lighter yellowish to light brown mandibles, antennae, and legs.

Type Material
Hita Garcia and Fisher (2014) - Holotype, pinned worker, MADAGASCAR, Central Madagascar (C. Schaufuss) (: CASENT0101697).