Afrotropical Tetramorium weitzeckeri species group

As defined by Hita Garcia et al. 2010, 2012, 2014.

This group was first defined by Bolton (1979, 1980) and included species from the Afrotropics and Malagasy regions. In its updated form, the group is largely Afrotropical with only one species, T. humbloti, ranging into the Malagasy region.

There is a key to all of the species, with the exception of Tetramorium mpala: Key to Tetramorium weitzeckeri-group species. There is a 2014 key to the species of the Tetramorium weitzeckeri species complex that includes T. mpala. Determining the species complex identity of workers in this species group can be accomplished using the key given below.

Diagnosis
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.

1

 * Antennal scrobe well developed and usually deep, with a distinct and often sharp margin all around, frontal carinae curve down ventrally between posterior eye level and occipital margin to form the posterior and ventral margins of the antennal scrobe, in a few species posterior margin weak but still visible; sculpture on cephalic dorsum often reduced, generally 3 or fewer rugae present between frontal carinae, in a few species up to 5 or 6, never more (Fig. 1A–B, E–F) . . . . . Tetramorium muralti complex


 * Antennal scrobe developed, but shallow, never with a sharp margin all around, frontal carinae almost reaching occipital margin and functioning as dorsal margin of antennal scrobe, ventral margin of antennal scrobe never differentiated; sculpture on cephalic dorsum never reduced, always at least 7 (generally distinctly more) longitudinal rugae present between frontal carinae (Fig. 1D, G–H) . . . . . 2

2
return to couplet #1
 * Petiolar node distinctly squamiform, in profile between 2.3 and 4.0 times higher than long (LPeI 25–43), shape in dorsal view always strongly transverse and elliptical, and between 2.2 and 3.7 times wider than long (DPeI 219–367) (Fig. 2A–B, E–F) . . . . . Tetramorium weitzeckeri complex


 * Petiolar node high nodiform, in profile around 1.3 to 2.0 times higher than long (LPeI 50–80), shape in dorsal view never elliptical or transverse, more an irregular polygon with rounded corners, and between 1.1 and 1.5 times wider than long (DPeI 110–154) (Fig. 2C–D, G–H) . . . . . Tetramorium edouardi complex

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

 * Tetramorium bendai
 * Tetramorium boltoni
 * Tetramorium guineense
 * Tetramorium humbloti
 * Tetramorium mpala
 * Tetramorium renae
 * Tetramorium sepultum
 * Tetramorium snellingi
 * Tetramorium tanaense
 * Tetramorium weitzeckeri

Key to Tetramorium weitzeckeri species complex

(2012) 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).

(2014) Tetramorium boltoni, T. guineense, T. renae and T. snellingi are species found predominantly in the equatorial rainforest belt, whereas the species T. humbloti, T. sepultum and T. weitzeckeri are distributed in the drier eastern and southern parts of sub-Saharan Africa. Tetramorium tanaense seems to be endemic to the coastal forests of Eastern Africa in Kenya and Tanzania, and T. bendai is only known from one collection in Burundi (without any ecological information at all). Tetramorium mpala also seems to have a very restricted distribution because it is only known from its type locality in Central Kenya.