Tetraponera gerdae (Stitz)

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 : 32-33

Tetraponera gerdae (Stitz)

( Figs 1 , 11 , 38 )

Sima gerdae Stitz 1911: 381 . Holotype (by monotypy) dealate queen, Amani , Tanzania (Vosseler) (ZMHB) [examined]. Imaged on AntWeb: FOCOL1171.

Sima (Tetraponera) gerdae Stitz ; Emery 1921: 27. Combination in Sima (Tetraponera) .

Tetraponera gerdae (Stitz) ; Wheeler 1922b: 797. Combination in Tetraponera .

Worker measurements (n = 10). HW 0.41–0.57, HL 0.62–0.87, LHT 0.36–0.56, CI 0.61–0.68, FCI 0.17–0.20, REL 0.27–0.32, REL2 0.43–0.48, SI 0.48–0.58, SI3 1.02–1.26, FI 0.46–0.57, PLI 0.82–0.93, PWI 0.62–0.76, LHT/ HW 0.85–1.00, CSC 0, MSC 0.

Worker diagnosis. Very similar to T. continua (see above) but head more elongate, on average (CI 0.61–0.68); petiole less slender (PLI 0.82–0.93), the petiolar node higher ( PH /HW 0.56–0.67) ( Fig. 11b ) and broader (DPW/HW 0.43–0.53), and postpetiole broader (PPW/HW 0.56–0.64) ( Fig. 1 ).

Comments. The holotype queen of T. gerdae , notable for its elongate head, closely matches a worker-associated queen from Kora, Kenya. The series of workers from Kora compare well with similar workers from Zimbabwe, Tanzania, Kenya and Eritrea. This species is closely similar to T. continua . An argument could be made for treating the two as conspecific, with the slight differences between them being attributable to geographical variation: continua -like workers (with a broader head and a more slender petiole and postpetiole) come from arid locations in northern Africa, and most gerdae -like samples (with a more elongate head and a more robust petiole and postpetiole) originate from east Africa. The distinctions are maintained, however, between the type worker of T. continua from Gotta, Ethiopia and an old series of T. gerdae -like workers collected by Penzig (1895) farther north, at Mount Lalamba, in what is now Eritrea ( Fig. 38 ). Thus a simple picture of geographically differentiated populations does not seem to apply. For now these two taxa are accorded status as separate species but it should be emphasized that sample sizes are limited and additional collections might erase the distinctions.

Distribution and biology. T. gerdae is known from scattered localities in mostly arid or semi-arid regions of east Africa ( Fig. 38 ). The series from Kora, Kenya is labeled “ex Acacia tortilis ”, and the workers from Eritrea were in “ Stereospermum dentatum ”. This latter collection was made by Penzig, who described the ants (misidentified as T. penzigi ) occupying live terminal branches of the Stereospermum tree, with brood and coccids, and behaving aggressively towards intruders ( Penzig 1895). Penzig considered Stereospermum dentatum (now a junior synonym of Stereospermum kunthianum ) to be a true myrmecophyte, but subsequent commentators have expressed doubt ( Bequaert 1922, Jolivet 1996), and T. gerdae is evidently not restricted to that plant. By contrast the related species, T. penzigi , nests only in the swollen stipular thorns of Vachellia drepanolobium .

Material examined ( BMNH, FHGC, LACM, MHNG, MNHN, MSNG, NHMW, PSWC, SAMC, UCDC, USNM, ZMHB). Eritrea: Semçnawî K’eyih Bahrî: Mount Lalamba , near Keren (Penzig) [locality from Penzig (1895: 467); given on labels as “Abessinien”, “Abissinia” and “Abyssinie”] ; Kenya: Baringo: Lake Baringo (Sibley, G.); Lake Bogoria , geyser (Peters, M.) ; Kajiado: Nguruman , nr. Sampu R., 723 m (Copeland, R.) ; Murang’a: Kora (West, C.) ; Samburu: Barsaloi lugga (Dewhurst, C. F.); Tanzania : Kilimanjaro: Mkomazi Game Reserve , Kikolo plot (van Noort, S.) ; Tanga: Amani (Vosseler); Zimbabwe : Bulawayo: Bulawayo ( ZBC Radio Mast) (Gardiner, A. J.) .

Figures

FIGURES 1–3. Bivariate plots of various metric measurements in Tetraponera workers. 1a, petiole height (PH) against head width (HW) in T. continua (n = 5) and T. gerdae (n = 10); 1b, postpetiole width (PPW) against head width (HW), for the same individuals; 2, scape length (SL) against head width (HW) in T. emeryi (n = 12) and T. clypeata (n = 10); 3, petiole height (PH) against length of metatibia (LHT) in T. natalensis from Kenya and Tanzania (n = 13) and T. redacta (coastal Kenya) (n = 10).

FIGURES 10–12. Tetraponera allaborans group, workers, full-face (dorsal) view of head (a) and lateral profile of body (b). 10, T. furtiva, holotype, South Africa (CASENT0843646); 11, T. gerdae, Kenya (CASENT0842369); 12, T. liengmei, South Africa (CASENT0794351). Images from AntWeb (www.antweb.org); photographers Phil Ward (10), Zachary Griebenow (11), Matthew Prebus (12).

FIGURES 35–40. Distribution maps for Afrotropical Tetraponera. 35, T. clypeata (circles), T. tessmanni (triangles); 36, T. emeryi (circles), T. dispar (triangle); 37, T. exactor (circle), T. furtiva (triangle), T. liengmei (squares); 38, T. continua (circles), T. cortina (triangles), T. gerdae (squares); 39, T. pedana (circles), T. penzigi (triangles); 40, T. pumila (circles).