Tetramorium merina

Tetramorium merina appears to live in leaf litter.

Identification
A member of the Tetramorium schaufussii species complex of the Tetramorium schaufussii species group. Hita Garcia and Fisher (2014) - The following character combination separates T. merina from the remaining species of the T. schaufussii complex: larger species (HW 0.69–0.79; WL 1.01–1.10); head longer than wide (CI 92–95); eyes relatively large (OI 26–28); frontal carinae usually weakly developed, only slightly raised, often not better developed than cephalic rugulae, and usually fading out halfway between posterior eye margin and posterior head margin; propodeal spines reduced to very short triangular teeth/denticles (PSLI 8–11), propodeal lobes short and triangular, always appearing more voluminous than propodeal teeth, and spines and lobes not strongly inclined towards each other; petiolar node rounded nodiform to rounded high nodiform, in profile around 1.6 to 1.8 times higher than long (LPeI 57–64), in dorsal view around 1.2 times wider than long (DPeI 117–124); dorsum of promesonotum with at least ten pairs of long, fine, standing hairs, propodeum without standing pilosity, and both waist segments with few long pairs each; body uniformly light to dark brown, gaster often darker, appendages usually lighter.

Tetramorium merina is only moderately distinct within the T. schaufussii complex, and can be confused with several other species. The possession of large eyes (OI 26–28) separates T. merina from Tetramorium pseudogladius (OI 20), and the petiolar node, which in dorsal view is around 1.2 times wider than long (DPeI 117–124) distinguishes it from Tetramorium nassonowii since the petiolar node of the latter in dorsal view is between 1.0 to 1.2 times longer than wide (DPeI 87–98). Tetramorium merina with its very short propodeal teeth (PSLI 8–11) is also not likely to be mistaken for Tetramorium scutum, which possesses much longer propodeal spines (PSLI 22–24) and relatively well-developed propodeal lobes. Also, in T. scutum the propodeal spines and lobes are strongly inclined towards each other, a condition absent in T. merina. Tetramorium rala, which is also the smallest species of the complex (HW 0.46–0.49; WL 0.58–0.64), has relatively long propodeal spines (PSLI 21–25), and the body is very bright yellowish to light brown, and thus not confusable with T. merina. In addition, the latter has numerous pairs of long, fine, standing hairs on each waist segment distinguishing it from Tetramorium sikorae, which lacks any standing pilosity on the waist segments.

The species closest to T. merina are Tetramorium monticola, Tetramorium obiwan, Tetramorium schaufussii, and Tetramorium xanthogaster, and the differentiation between these is sometimes challenging. Tetramorium merina is a relatively large species (HW 0.69–0.79; WL 1.01–1.10) and could be confused with T. obiwan, which is in the same size range or even larger (HW 0.71–0.84; WL 1.00–1.20), or T. xanthogaster, which is usually smaller but reaches its upper size limit in the range of T. merina (HW 0.54–0.75; WL 0.72–1.05). However, T. obiwan has longer antennal scapes (SI 77–82), better-developed frontal carinae, and usually no standing pilosity on the waist segments contrasting with the shorter antennal scapes (SI 72–75), much weaker frontal carinae and the presence of several pairs of standing pilosity on the waist segments of T. merina. Furthermore, T. xanthogaster, despite being a very variable species throughout its range, can be easily separated from T. merina in the central Highlands where they are usually found occurring in sympatry. In this region T. xanthogaster is always strongly bicoloured with head and mesosoma very dark brown to black, strongly contrasting with the yellow to light brown waist segments and gaster. Also, T. xanthogaster usually has long, fine, standing pilosity on the propodeal dorsum while T. merina lacks any standing pilosity on the propodeum. Few other diagnostic characters separate both species, but the fact that they co-occur in sympatry in several localities without any intermediate forms is a good indication of their heterospecificity. Tetramorium monticola, which is found in the northeast and north of Madagascar, does not co-occur with T. merina, and both are relatively easy to differentiate. In T. monticola the frontal carinae are relatively better developed, the cephalic dorsum between them has nine to thirteen relatively regularly shaped, mostly unbroken rugae, and the propodeum is armed with short to medium-sized spines (PSLI 18–22) while T. merina has much weaker frontal carinae with eight to ten, often broken and irregular rugulae, and the propodeum is only armed with small teeth/denticles (PSLI 8–11).

The most difficult species to separate from T. merina is certainly T. schaufussii. As is the case with T. xanthogaster, T. merina is also found regularly in sympatry with T. schaufussii, and again, they are separable based on a few characters. Tetramorium merina is larger in size (HW 0.69–0.79; WL 1.01–1.10), has a broader head (CI 92–95), and longer (though not significantly so) antennal scapes (SI 72–75) than T. schaufussii (HW 0.51–0.68; WL 0.73–0.93; CI 86–90; SI 66–73). These differences seem difficult to assess without measuring, except for body size, which however, can vary from one population to another and therefore should only be used with caution. Nevertheless, where the two species are found in sympatry (often they are found within the same litter sample) they can be easily discriminated based on body size. In contrast to T. schaufussii and T. xanthogaster, which are both very variable species, T. merina is very stable in its morphological appearance.

Key to Tetramorium schaufussii  species complex workers

Distribution
Tetramorium merina is only known from the Central Highlands of Madagascar. Its distribution ranges from the two southernmost localities Atsirakambiaty and Ankazomivady through Manjakatompo north to Andranomay, Ambohitantely and Sohisika. (Hita Garcia and Fisher 2014)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Habitat
All localities are montane rainforests situated at elevations of 1410 to 1700 m

Nomenclature

 *  merina. Tetramorium merina Hita Garcia & Fisher, 2014: 111, figs. 20C, 40B, 42D, 44D, 46D, 47C, 48C, 49B, 50, 65 (w.) MADAGASCAR.

Worker
(N=12). HL 0.75–0.84 (0.79); HW 0.69–0.79 (0.73); SL 0.51–0.57 (0.54); EL 0.18–0.21 (0.19); PH 0.37–0.40 (0.39); PW 0.52–0.57 (0.54); WL 1.01–1.10 (1.05); PSL 0.06–0.10 (0.08); PTL 0.16–0.20 (0.18); PTH 0.28–0.31 (0.30); PTW 0.19–0.24 (0.22); PPL 0.21–0.24 (0.22); PPH 0.28–0.30 (0.29); PPW 0.27–0.31 (0.29); CI 92–95 (93); SI 72–75 (74); OI 26–28 (26); DMI 50–53 (52); LMI 36–38 (37); PSLI 8–11 (10); PeNI 36–43 (40); LPeI 57–64 (61); DPeI 117–124 (120); PpNI 50–56 (53); LPpI 71–80 (75); DPpI 128–136 (131); PPI 125–142 (133).

Head longer than wide (CI 92–95); posterior head margin weakly concave. Anterior clypeal margin with distinct median impression. Frontal carinae usually weakly developed, only slightly raised, often not better developed than cephalic rugulae, and usually fading out halfway between posterior eye margin and posterior head margin. Antennal scrobes present but weak, shallow and without clear and distinct posterior and ventral margins. Antennal scapes short, not reaching posterior head margin (SI 72–75). Eyes relatively large (OI 26–28). Mesosomal outline in profile flat to weakly convex, comparatively low and elongate (LMI 36–38), weakly marginate from lateral to dorsal mesosoma; promesonotal suture absent; metanotal groove very weakly developed to absent. Propodeal spines reduced to very short, triangular, and acute or blunt teeth/denticles (PSLI 8–11), propodeal lobes short, triangular, and acute or blunt, always appearing more voluminous than propodeal teeth, spines and lobes not strongly inclined towards each other. Petiolar node in profile nodiform to high nodiform with well-rounded antero- and posterodorsal margins, around 1.6 to 1.8 times higher than long (LPeI 57–64), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about same height, petiolar dorsum weakly to moderately convex; petiolar node in dorsal view around 1.2 times wider than long (DPeI 117–124), in dorsal view pronotum between 2.3 to 2.7 times wider than petiolar node (PeNI 36–43). Postpetiole in profile globular, approximately 1.3 to 1.4 times higher than long (LPpI 71–80); in dorsal view around 1.3 to 1.4 times wider than long (DPpI 128–136), pronotum between 1.8 to 2.0 times wider than postpetiole (PpNI 50–56). Postpetiole in profile appearing slightly lower or of same height but thicker than petiolar node, postpetiole in dorsal view around 1.3 to 1.4 times wider than petiolar node (PPI 125–142). Mandibles unsculptured, smooth, and shiny; clypeus weakly longitudinally rugulose with two to five lateral rugulae, median area usually completely unsculptured or only weakly sculptured, median ruga usually absent, at most traces present, lateral rugulae often interrupted or irregularly shaped, but at least one lateral rugula well developed on each side; cephalic dorsum between frontal carinae irregularly longitudinally rugulose with eight to ten rugulae; rugulae running from posterior clypeal margin to posterior head margin, often meandering, broken or with cross-meshes; scrobal area mostly unsculptured and laterally merging with surrounding reticulate-rugose sculpture present on lateral head; ground sculpture on head weakly to moderately punctate. Dorsum of mesosoma reticulate-rugose, especially anteriorly, to irregularly longitudinally rugose, lateral mesosoma mostly irregularly longitudinally rugose; ground sculpture on mesosoma weak to absent. Forecoxae mainly unsculptured, smooth, and shining. Waist segments and gaster unsculptured, smooth, and shining. Dorsum of head with numerous pairs of long, fine, standing hairs; dorsum of mesosoma with at least eleven or twelve pairs of long, standing hairs ranging from anterior pronotum to posterior mesonotum, propodeum without long, standing pilosity; petiole usually with two pairs and postpetiole with three to four pairs; first gastral tergite with short, scarce, appressed pubescence in combination with abundant, long, standing hairs. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with decumbent to suberect hairs. Body uniformly light brown to dark brown, gaster often of darker brown, appendages usually lighter.

Type Material
Holotype, pinned worker, MADAGASCAR, Antananarivo, Réserve Spéciale d’Ambohitantely, Forêt d’Ambohitantely, 20.9 km 72° NE Ankazobe, 18.22528°S, 47.28683°E, 1410 m, montane rainforest, ex rotten log, collection code BLF03710, 17.– 22.IV.2001 (B.L. Fisher et al.) (: CASENT0437226). Paratypes, 13 pinned workers with same data as holotype (: CASENT0437223; CAS: CASENT0437222; CASENT0437228; CASENT0437229; CASENT0437230; CASENT0437231; CASENT0437232; CASENT0437233; : CASENT0437225).

Etymology
The new species is named for the Merina people of Madagascar, in honor of their culture and language. The distribution range of T. merina fits the boundaries of the traditional Merina kingdom very well. The species epithet is an arbitrary combination of letters, thus invariant.