Tetramorium robitika, Garcia & Fisher, 2012

Garcia, Francisco Hita & Fisher, Brian L., 2012, The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region — taxonomy of the T. bessonii, T. bonibony, T. dysalum, T. marginatum, T. tsingy, and T. weitzeckeri species groups, Zootaxa 3365, pp. 1-123 : 75-78

Tetramorium robitika sp. n.

(figs 71, 73, 110, 111, 112)

Holotype worker, MADAGASCAR, Antananarivo, Manjakatompo , 17 km W Ambatolampy, 19.35 S, 47.31667 E, 1500 m, disturbed montane rainforest, sifted litter (leaf mold, rotten wood), collection code BLF7998, 11.II.2003 (D. Silva, D. Andriamalala et al.) ( CASC: CASENT0056338 ) . Paratypes, ten workers with same data as holotype ( CASC: CASENT0056206 , CASENT0056207 , CASENT0056210 , CASENT0056211 , CASENT0056333 , CASENT0056334 , CASENT0056335 , CASENT0056336 , CASENT0056337 ; MHNG: CASENT0056209 ); and six workers from Antananarivo, Manjakatompo , 19º 21' S, 47º 19' E, 1600 m, montane rainforest, sifted litter (leaf mold, rotten wood), collection code PSW11971, 20.II.1993 (P.S. Ward) ( BMNH: CASENT0247149 , CASENT0247150 ) .

Diagnosis

The subsequent set of characters clearly distinguishes T. robitika from all other species of the T. dysalum group: antennal scapes relatively short (SI 68–71); propodeal spines comparatively short (PSLI 20–22); petiolar node high nodiform with anterodorsal and posterodorsal margins at approximately same height, dorsum not tapering backwards posteriorly; dorsum of mesosoma with longitudinally arranged rugae.

Description

HL 0.62–0.72 (0.68); HW 0.59–0.69 (0.65); SL 0.41–0.49 (0.45); EL 0.12–0.15 (0.14); PH 0.32–0.38 (0.35); PW 0.43–0.51 (0.48); WL 0.74–0.88 (0.81); PSL 0.14–0.16 (0.14); PTL 0.14–0.17 (0.15); PTH 0.25–0.29 (0.28); PTW 0.19–0.23 (0.21); PPL 0.17–0.22 (0.20); PPH 0.24–0.29 (0.27); PPW 0.26–0.31 (0.29); CI 95–96 (96); SI 68–71 (69); OI 20–23 (21); DMI 57–62 (59); LMI 42–43 (43); PSLI 20–22 (21); PeNI 42–45 (44); LPeI 54–57 (56); DPeI 133–142 (137); PpNI 58–62 (60); LPpI 68–75 (72); DPpI 144–155 (147); PPI 133–143 (137) (ten measured).

Head longer than wide (CI 95–96). Anterior clypeal margin with distinct median impression. Frontal carinae well-developed and running to posterior head margin, halfway between posterior eye and posterior head margins weaker but still distinct. Antennal scrobes narrow and faint. Antennal scapes short, not reaching posterior head margin (SI 68–71). Eyes small to moderate (OI 20–23). Mesosomal outline in profile flat to slightly convex, moderately marginate from lateral to dorsal mesosoma, promesonotal suture absent, metanotal groove usually very weak or absent; mesosoma comparatively stout and compact (LMI 42–43). Propodeum armed with elongatetriangular, short to medium-sized spines (PSLI 20–22). Propodeal lobes short and triangular, much less voluminous than propodeal spines. Petiolar node in profile rounded high nodiform, approximately 1.8 times higher than long (LPeI 54–57), anterior and posterior faces parallel and anterodorsal and posterodorsal margins situated at same height, dorsum not tapering backwards posteriorly; node in dorsal view of elliptical shape and 1.3 to 1.4 times wider than long (DPeI 133–142). Postpetiole in profile rounded and weakly anteroposteriorly compressed, approximately 1.3 to 1.5 times higher than long (LPpI 68–75), in dorsal view approximately 1.5 times wider than long (DPpI 144–155). Postpetiole in profile approximately as voluminous as petiolar node, in dorsal view approximately 1.3 to 1.4 times wider than petiolar node (PPI 133–143). Mandibles strongly longitudinally rugose; clypeus with distinct median longitudinal ruga and one or two weaker rugulae at each side; cephalic dorsum between frontal carinae with seven to nine longitudinal rugae, rugae running to posterior head margin and often with cross-meshes; lateral and ventral head reticulate-rugose to longitudinally rugose; ground sculpture on head generally faint. Mesosoma laterally with irregular rugae or rugulae, dorsally longitudinally rugose, rugae weakly meandering and sometimes with few cross-meshes. Petiole and postpetiole unsculptured, smooth and shining. All dorsal surfaces of body with short to moderately long, erect or suberect pilosity. Head, mesosoma, waist segments, and gaster brown, gaster weakly darker, and appendages of lighter brown to dark yellow.

Notes

Tetramorium robitika is currently only known from the type locality, which is a montane rainforest located at an altitude of 1500 m to 1600 m, and it appears to live in leaf litter.

The possession of short propodeal spines or teeth separates T. robitika (PSLI 20–22) from most other species of the group, which have much longer spines (PSLI 27–44) save for T. macki (PSLI 21–24) and T. orc (PSLI 19–23). However, the latter two can be distinguished easily from T. robitika due to differences in their petiolar node shape. The nodes of T. macki and T. orc are moderately cuneiform with an anterodorsal margin situated much higher than the posterodorsal margin, which causes the dorsum to taper noticeably backwards posteriorly. This contrasts strongly with the high rounded nodiform node shape observed in T. robitika , which has anterodorsal and posterodorsal margins at approximately the same height, and the dorsum does not taper backwards posteriorly.

Ignoring the propodeal spine length, however, T. robitika is very similar to T. vohitra . Both species share most morphological characters, especially short to moderate gastral pilosity, and have a similar general gestalt, although they differ in their morphometric ranges and a few key characters. Tetramorium robitika possesses a slightly longer head (CI 95–96), shorter antennal scapes (SI 68–71), shorter propodeal spines (PSLI 20–22), and the postpetiole is narrower than the petiolar node (PPI 133–143) in comparison to T. vohitra (SI 97–101; SI 71–74; PSLI 28–31; PPI 142–152). Also, the mandibles of T. robitika are distinctly sculptured while they are unsculptured in T. vohitra , and this character is generally very stable within the species of the group, except in T. steinheili . However, both species are only known from their respective type localities, which are widely separated from each other. This allopatric distribution could indicate that they are both geographical varieties of the same species. Nevertheless, considering all the above data, we consider T. robitika and T. vohitra as distinct species on the basis of the morphometric and morphological differences mentioned above.

Etymology

The epithet of the new species is an arbitrary combination of letters. The new species is dedicated to Caitlin Robitaille for her support to discover and identify life on earth.

Material examined

MADAGASCAR: no locality data; Antananarivo, Manjakatompo, 19º 21' S, 47º 19' E, 1600 m, montane rainforest, 20.II.1993 (P.S. Ward); Antananarivo, Manjakatompo, 17 km W Ambatolampy, 19.35 S, 47.31667 E, 1500 m, 11.II.2003 (D. Silva, D. Andriamalala et al.).