Tetraponera latifrons (Emery)

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 : 62-64

Tetraponera latifrons (Emery)

( Figs 34 , 46 )

Sima (Pachysima) latifrons Emery, 1912: 98 . Holotype (by monotypy), alate queen, Gabon (Staudinger) (MSNG) [examined]. Imaged on AntWeb : CASENT0904042.

Sima (Pachysima) latifrons Emery ; Santschi 1914b: 288. Description of worker, male.

Pachysima latifrons (Emery) ; Wheeler 1918: 305, 308. Combination in Pachysima ; description of larva.

Tetraponera latifrons (Emery) ; Ward 1990: 488. Combination in Tetraponera .

Tetraponera latifrons (Emery) ; Chomicki et al. 2015: figure S1. Placement in molecular phylogeny.

Worker measurements (n = 8). HW 1.57–2.20, HL 1.68–2.45, LHT 1.21–1.75, CI 0.90–0.97, FCI 0.28–0.35, REL 0.27–0.30, REL2 0.29–0.32, SI 0.50–0.52, SI3 1.61–1.74, FI 0.39–0.41, PLI 0.62–0.79, PWI 0.77–0.85, LHT/HW 0.76–0.81, CSC 1–6, MSC 27–45.

Worker diagnosis. Similar to T. aethiops except as follows: frontal carinae separated by a distance greater than one quarter of head width (FCI 0.28–0.35); profemur more robust (FI 0.39–0.41), legs shorter (LHT/HL 0.71–0.75); anteroventral petiolar tooth robust and prominent, directed posteroventrally, not followed by a second, more posterior tooth; anteroventral tooth of postpetiole well developed, spiniform, not followed posteriorly by a prominent protrusion ( Fig. 34b ). Mandibles smooth and shiny with scattered fine punctures. Standing pilosity more common (MSC 27–45), notably in the form of a dense brush of forwardly-directed hairs on the clypeus and by conspicuous hairs on the pronotum, propodeum, petiole and postpetiole.

Comments. T. latifrons is more setose, shorter-legged, and smaller (on average) than T. aethiops . See under the latter species for further discussion of the differences between the two.

Distribution and biology. Another obligate Barteria inhabitant, T. latifrons is broadly sympatric with T. aethiops , but evidently less common. At a study site in Sapoba Forest, Nigeria, Janzen (1972) reported that both species had similar biology, but that the colonies occurred in a ratio of about 1:100. More recent work in Gabon has shown that the two species have differing hostplant preferences and protective behavior, with T. latifrons occurring more frequently in Barteria dewevrei , and T. aethiops being preferentially associated with Barteria fistulosa and showing a stronger reaction to leaf disturbance ( Kokolo et al. 2019). Given differences in morphology of the workers and larvae ( Wheeler 1918; Wheeler & Wheeler 1956) it seems probable that there are additional biological differences between the two species yet to be discovered.

Material examined ( AMNH, BMNH, CASC, CUIC, LACM, MCZC, MHNG, MNHN, MSNG, NHMW, PSWC, SAMC, USNM). Cameroon: Sud-Ouest: Victoria (Malkin, B.) ; Central African Republic: Sangha-Mbaéré: P.N. Dzanga-Ndoki, 38.6 km 173° S Lidjombo , 350 m (van Noort, S.); P.N. Dzanga-Ndoki, 5.9 km 72° ENE Bayanga, 410 m (Fisher, B. L.); P.N. Dzanga-Ndoki, Mabéa Bai, 21.4 km 53° NE Bayanga, 510 m (Fisher, B. L.) ; DR Congo: Haut-Uélé: Niangara (c.u.); Niangara (Lang, H. O.); Niangara (Lang; Chapin); Kasaï Oriental: Kondué (Luja); Kongo Central: 75 mi W Popokabaka (Ross, E. S.; Leech, R. E.) ; Gabon: province unknown: “Gabon” ( Staudinger ); “Gabun” (c.u.) ; Nigeria: Edo: Ogbesse Benin (Box, H. E.); Sapoba For. Reserve , 20 km S Benin City (Janzen, D. H.) ; Republic of Congo: Brazzaville: Brazzaville [as “ de Brazza ”] (c.u.); Pool : Lesio-Loun Park , 330 m (Braet; Sharkey); Lesio-Loun Park, 330 m (Sharkey; Braet) .

Concluding remarks

As with other ant genera centered in tropical latitudes, such as Crematogaster and Camponotus , the species-level taxonomy of Tetraponera has been burdened by a plethora of named but poorly characterized taxa. Although the current study has uncovered new species, it has also highlighted a considerable amount of “taxonomic inflation” due to the profligate naming of species, subspecies, and varieties by Forel, Santschi, and other workers in the late nineteenth and early twentieth centuries. These individuals focused on slight morphological differences, worked with small sample sizes, and had inchoate views about the nature of species. The taxonomic hypotheses in this paper are based on adherence to the biological species concept ( Mayr 1942; Coyne & Orr 2004) and on a recognition that species can encompass significant genetic variation and population structure. The conclusions about species boundaries should be considered provisional, however, and subject to refinement with further evidence. A key point is that when two closely similar forms show (1) overlapping geographical distributions, and (2) no diminution of their differences in sympatry, this is a compelling argument for treating them as separate species ( Tobias et al. 2010; Galtier 2019). Conversely, allopatric variants present a more difficult situation, and require careful assessment before being treated as heterospecific. Are such allopatric forms connected by intermediate populations—or likely to be so, under more comprehensive geographic sampling? Do they show a degree of difference comparable to that of closely related sympatric species ( Tobias et al. 2010)? Such joint scrutiny of phenotypic variation and geographical distribution is a critical component of the methodology employed here. In addition, published phylogenetic studies of Pseudomyrmecinae ( Ward & Downie 2005; Chomicki et al. 2015) and ongoing phylogenomic ( UCE) work (Ward, in prep.) have provided useful insights.

Based on current understanding, the ant genus Tetraponera is represented in the Afrotropical region by 28 species in mainland Africa, and approximately 40 species in Madagascar. Given the relatively high frequency of rare taxa—five of the eleven newly described species are known from just a single locality, for example—it seems almost certain that additional species await discovery. Nevertheless, the contrast between continental Africa and Madagascar is likely to remain, pointing to opportunities for diversification on the island that are not present on the mainland.

This study has also improved the delimitation of specialized, myrmecophyte-inhabiting species of Tetraponera and their relatives. This lays the foundation for detailed comparative studies that could provide insight into the evolution of specialized ant-plant associations. Particular attention should be paid to the T. allaborans group in Africa: it includes several poorly known species, related to the well-studied T. penzigi , that appear to have a propensity to inhabit live stems and associate with Coccoidea. Studies of their ecology and behavior should prove enlightening.

Figures

FIGURES 33–34. Tetraponera rufonigra group workers, full-face (dorsal) view of head (a) and lateral profile of body (b). 33, T. aethiops, Uganda (CASENT0794322); 34, T. latifrons, DR Congo (CASENT0217593). Images from AntWeb (www.antweb. org); photographers Matthew Prebus (33), Estella Ortega (34).

FIGURES 41–46. Distribution maps for Afrotropical Tetraponera. 41, T. andrei (circles), T. anthracina (triangles), T. insularis (square); 42, T. caffra (circles), T. redacta (triangles); 43, T. mocquerysi (circles), T. schulthessi (triangles); 44, T. natalensis (circles), T. setosa (triangle); 45, T. aethiops (circles), T. kosi (triangle); 46, T. latifrons (circles).