Afrotropical Tetramorium weitzeckeri species group

The morphological species group, and complexes, as defined by: Hita Garcia, F.; Fischer, G.; Peters, M. K. 2010. Taxonomy of the Tetramorium weitzeckeri species group (Hymenoptera: Formicidae) in the Afrotropical zoogeographical region. Zootaxa 2704:1-90.

This group was first defined by Bolton (1979, 1980) and included species from the Afrotropics and Malagasy regions. The treatment below is for the Afrotropical members of the group (26 species). There is a Key to Tetramorium weitzeckeri-group species.

weitzeckeri species group

 * Tetramorium akengense
 * Tetramorium bendai
 * Tetramorium boltoni
 * Tetramorium edouardi
 * Tetramorium flavithorax
 * Tetramorium guineense
 * Tetramorium humbloti
 * Tetramorium intermedium
 * Tetramorium kakamega
 * Tetramorium mkomazi
 * Tetramorium muralti
 * Tetramorium occidentale
 * Tetramorium philippwagneri
 * Tetramorium pinnipilum
 * Tetramorium renae
 * Tetramorium robertsoni
 * Tetramorium rogatum
 * Tetramorium rubrum
 * Tetramorium schoutedeni
 * Tetramorium sepultum
 * Tetramorium snellingi
 * Tetramorium susannae
 * Tetramorium tanaense
 * Tetramorium trirugosum
 * Tetramorium weitzeckeri
 * Tetramorium zonacaciae

The T. weitzeckeri species group can be defined by the following combination of characters that separate them distinctly from all other Afrotropical Tetramorium species groups:

1. 11-segmented antennae

2. anterior clypeal margin generally with median impression, reduced in some smaller species

3. petiolar node generally squamiform, distinctly antero-posteriorly compressed, in profile much higher	than long, and in dorsal view much wider than long; if not squamiform then petiolar node high nodiform but still higher and wider than long, never blocky nodiform with sharply 	defined angles

4. postpetiole squamiform, cuneiform, or rounded, never nodiform

5. petiole and postpetiole unsculptured in most species, in a few species distinct sculpturation present, gaster always smooth and shiny

6. body hairs usually simple, but distinctly modified in Tetramorium pinnipilum (pectinate / pinnate), Tetramorium rogatum (clavate), and Tetramorium zonacaciae (broad, flattened, and 	appressed); never regularly branched bifid, trifid nor quadrifid;

7. hairs on first gastral tergite, if present, never short and dense

8. dorsal surfaces of antennal scapes and hind tibiae usually with fine, short pubescence which is appressed to subdecumbent, never with long projecting hairs

9. sting appendage spatulate

The group can be further divided into 3 distinctive complexes.

edouardi complex
The edouardi complex contains nine species, most of which seem to inhabit open habitats, except for T. pinnipilum and T. rogatum that prefer the rain forest leaf litter. Interestingly, this species complex seems to be absent from Southern Africa. The most important character to separate the edouardi complex from the muralti and  weitzeckeri complexes is the shape of the petiolar node which is always high nodiform, in dorsal view only slightly wider than long (DPeI 110 - 154), and in lateral view usually significantly less than twice as high as long (LPeI 50 - 80). The shape of the petiolar node in dorsal view is usually more like an irregular hexagon with rounded corners and not a more or less transverse ellipse as can be seen in the other two complexes. Furthermore, the antennal scrobe is much less developed compared to the muralti complex because it is shallow, often narrow, and the posterior and ventral margins are never sharply defined. Additionally, in the T. edouardi complex the cephalic sculpturation is never reduced and there are always at least seven longitudinal rugae present between the frontal carinae. The species complex can be split into bicoloured species with small eyes and simple pilosity (Tetramorium philippwagneri, Tetramorium schoutedeni), species with specialized or reduced pilosity (Tetramorium mkomazi, Tetramorium pinnipilum, Tetramorium rogatum, Tetramorium zonacaciae), and into core species without significant specializations (Tetramorium edouardi, Tetramorium robertsoni, Tetramorium rubrum).

muralti complex
A group of relatively small, generally darkly coloured rain forest species which all seem to live in the leaf litter stratum. This complex is mostly restricted to Western and Central Africa with one species also known from Western Kenya. The single best diagnostic character to distinguish this species complex from the edouardi and  weitzeckeri complexes is the development of the antennal scrobe. It is usually well developed and deep with a distinct margin all around. The frontal carinae are generally strongly developed and curve down ventrally between posterior eye level and posterior margin of head to form the posterior and ventral margin of the antennal scrobe. Another difference compared to the edouardi and weitzeckeri complexes is the predominance of reduced cephalic and mesosomal sculpturation. The longitudinal rugae between the frontal carinae which are present in all species of the edouardi and weitzeckeri complexes, usually with more than seven, are reduced in most species of the muralti complex. This reduction differs from species to species. For example, some species like T. susannae and T. occidentale possess only one median ruga on the cephalic dorsum, T. muralti shows typically three mostly unbroken rugae, while in T. intermedium there are six. Furthermore, the petiolar node in the muralti complex is squamiform in all species, more than 1.75 times wider than long (DPeI 179 - 354) and generally more than twice as high as long (LPeI 30 - 50), although it can vary in dorsal view from thickly squamiform as in T. intermedium (DPeI 179 - 212) to strongly squamiform and transverse in T. susannae (DPeI 307 - 353). The shape of the petiolar node in dorsal view is generally elliptic though sometimes with a small anterior median bulge. The species complex can be further divided into species with distinctive longitudinal rugae or rugulae on the mesosomal dorsum (Tetramorium flavithorax, Tetramorium intermedium, Tetramorium trirugosum), species with a mostly unsculptured mesosoma and an impressed anterior clypeal margin (Tetramorium akengense, Tetramorium kakamega, Tetramorium occidentale), and species with a mostly unsculptured mesosoma and an entire anterior clypeal margin (Tetramorium muralti, Tetramorium susannae).

weitzeckeri complex
The species of this complex can be found in most of the Afrotropical region although each one has its particular distribution range. T. boltoni, T. guineense, T. renae and T. snellingi are forest species, distributed throughout the Guineo-Congolian forest zone while the rest of the complex lives in open habitats in Eastern and Southern Africa. As opposed to the petiolar shape in the edouardi complex, species of the weitzeckeri complex all possess a distinctly squamiform petiolar node, in dorsal view distinctly more than twice as wide as long, often much more (DPeI 219 - 367), in profile much more than twice as high as long (LPeI 25 - 43). The shape of the petiolar node in dorsal view is always elliptical as opposed to the irregularly hexagonal shape observed in the edouardi complex. In addition, the development of the antennal scrobe within the weitzeckeri group resembles the condition in the edouardi complex. The scrobe is less strongly developed than in the muralti complex, usually shallow, narrow, and without a well-defined ventral margin. As in the edouardi complex, the cephalic sculpturation is never reduced, with at least seven longitudinal rugae between the frontal carinae. The species complex can be further divided into species with standing hairs on the first gastral tergite (Tetramorium boltoni, Tetramorium guineense, Tetramorium renae, Tetramorium snellingi, Tetramorium weitzeckeri) and those without standing pilosity on this tergite (Tetramorium bendai, Tetramorium humbloti, Tetramorium sepultum, Tetramorium tanaense).