Tetraponera ambigua (Emery, 1895)

Ward, Philip S., 2022, The ant genus Tetraponera (Hymenoptera: Formicidae) in the Afrotropical region: taxonomic review and key to species, Zootaxa 5102 (1), pp. 1-70 : 43-44

Tetraponera ambigua -group

Worker diagnosis (from Ward 2006). Small to medium-sized species (HW 0.51–0.91); masticatory margin of mandible with four (in one species six) teeth; basal margin lacking distinct teeth (small denticle may be present near apicobasal tooth) and shorter than masticatory margin; labrum without prominent teeth or tubercles; anteromedial margin of clypeus crenulate or entire; distance between frontal carinae notably exceeding basal scape width (FCI 0.15–0.25); scape length one half to two thirds of head width (SI 0.52–0.65); compound eyes directed anteromedially; head capsule without ocelli or with a lateral pair only (if present usually weakly developed), median ocellus lacking; pronotum with soft lateral margination; mesonotum either extending to propodeum or separated from it by a weakly differentiated metanotum; posteroventral margin of petiole well separated from helcium venter; metabasitarsal sulcus generally absent (present in one species); upper half of mesosternum sparsely pubescent; appressed pubescence dense on abdominal tergite 4. Worker caste dimorphic, with a discrete soldier (major worker) subcaste.

Comments. This group of four species was revised by Ward (2006) which should be consulted for more information. Note that the key to workers in Ward (2006) has been expanded here to include the queen caste. No new taxa or major range extensions have been discovered since the earlier treatment. The distribution of T. parops is now known to include Mozambique.

In a paper on the ants of Pongara National Park in Gabon, Braet & Taylor (2018) resurrected two junior synonyms in the Tetraponera ambigua -group, T. ophthalmica angolensis Santschi (previously synonymized under T. ambigua by Ward (2006: 123)) and Tetraponera ophthalmica unidens Santschi (previously synonymized under T. ophthalmica by Ward (2006: 126)), and raised them to species. These actions are considered unjustified and are here reversed, based on the following reasoning.

There are four syntype workers of Tetraponera ophthalmica angolensis in NHMB (one imaged on AntWeb: CASENT0915536). Direct examination and measurement of these specimens reveals that their size (HW ~0.65), relative eye size (REL ~0.43), frontal carinal configuration (FCI ~0.19), petiole shape (PLI ~0.60), pilosity, and maculation fall within the range of variation encompassed by T. ambigua (see Ward 2006: 125). The syntype dealate queen of Tetraponera ophthalmica unidens in MRAC (RMCAENT000017747) was also directly examined and shown to differ in no substantial way from worker-associated queens of T. ophthalmica from Cameroon, Central African Republic and Uganda. While there may be additional, cryptic species in the T. ambigua -group, no compelling evidence was presented by Braet & Taylor (2018) for resurrection of the names T. angolensis and T. unidens , and they are here returned to the status of junior synonyms (syn. rev.).

Braet & Taylor (2018) instituted other poorly justified taxonomic changes in their paper on the ants of Pongara National Park. They used an outdated subfamily classification, and they ignored or contradicted the results of recent taxonomic studies on the genera Carebara , Crematogaster and Nylanderia . Such actions retard progress in ant systematics and should have been moderated by a more rigorous peer review process.

In a more recent paper Taylor & McGavin (2020) promulgated further unwarranted taxonomic changes in the Tetraponera ambigua group. Their study was concerned with ants inhabiting Vachellia and other trees in Mkomazi Game Reserve, Tanzania. Based on questionable evidence Taylor & McGavin (2020) resurrected two additional synonyms of Tetraponera ambigua : T. bifoveolata (Mayr) and T. erythraea (Emery) . T. bifoveolata was said to be distinguished from T. ambigua by the presence of a major worker (soldier) caste, while T. erythraea was claimed to have more abundant mesosomal pilosity and an “alitrunk [sic] profile in three shallow convexities”. These arguments have little merit. Major workers are found in all species of the T. ambigua group (Ward 1996), and T. ambigua workers show modest (and continuous) variation in mesosomal pilosity, with MSC values ranging from 12 to 44. The syntype workers of T. ambigua , T. bifoveolata and T. erythraea fall within this range of variation (types directly examined). The difference in mesosomal profile between T. ambigua and T. erythraea is also of dubious value. T. ambigua workers from more northern locations, including Yemen (the type locality of T. erythraea ), tend to have a better developed metanotal impression, which enhances the convexity of the mesonotum and the dorsal face of the propodeum when viewed in profile, but this character is quite variable and has not been shown to have diagnostic value. The synonymy of T. bifoveolata and T. erythraea under T. ambigua is here reconfirmed (syn. rev.).

If the treatment of Tetraponera is indicative, then other taxonomic changes proposed in Taylor & McGavin (2020), involving the genera Camponotus , Crematogaster , Nesomyrmex , and Polyrhachis , require critical reexamination.