Tetramorium steinheili Forel, 1892

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 : 80-84

Tetramorium steinheili Forel, 1892

(figs 70, 78, 81, 82, 85, 87, 90, 91, 116, 117, 118, 119, 120, 121)

Tetramorium (Xyphomyrmex) steinheili Forel, 1892:520 . Lectotype worker [designated here], MADAGASCAR, Forêt d'Andrangoloaka ( MHNG: CASENT0101814 ) [examined]. Paralectotypes, two workers and two queens with same data as holotype ( MHNG: CASENT0101257 ; CASENT0101258 ; CASENT0101566 ); one queen from Imerina ( Sikora ) ( MHNG: CASENT0101801 ) [examined].

Diagnosis

Tetramorium steinheili can be best recognised within its species group by the following character combination: short antennal scapes (SI 71–76); eyes small to moderate (OI 21–23); propodeal spines long to very long (PSLI 27– 44); propodeal lobes variably long, but never long and spinose; petiolar node squamiform with anterodorsal margin situated slightly higher than posterodorsal margin, dorsum tapering backwards posteriorly; dorsum of mesosoma with longitudinally arranged rugae; hairs on first gastral tergite erect or suberect.

Description

HL 0.72–0.95 (0.86); HW 0.73–0.96 (0.86); SL 0.53–0.71 (0.63); EL 0.16–0.21 (0.18); PH 0.36–0.50 (0.44); PW 0.50–0.71 (0.63); WL 0.91–1.23 (1.10); PSL 0.20–0.40 (0.32); PTL 0.13–0.20 (0.17); PTH 0.30–0.40 (0.36); PTW 0.20–0.31 (0.27); PPL 0.21–0.32 (0.27); PPH 0.28–0.41 (0.35); PPW 0.27–0.40 (0.34); CI 96–102 (100); SI 71–76 (73); OI 21–23 (21); DMI 55–60 (57); LMI 38–44 (40); PSLI 27–44 (37); PeNI 39–45 (42); LPeI 42–50 (47); DPeI 150–168 (157); PpNI 49–60 (55); LPpI 64–84 (77); DPpI 117–138 (127); PPI 119–137 (130) (30 measured).

Head usually approximately as long as wide, sometimes longer than wide to wider than long (CI 96–102). Anterior clypeal margin medially impressed. Frontal carinae well-developed, usually ending at posterior head margin. Antennal scrobes shallow, narrow, and very weakly developed. Antennal scapes short, not reaching posterior head margin (SI 71–76). Eyes comparatively small to moderate (OI 21–23). Mesosomal outline in profile flat, weakly to moderately marginate from lateral to dorsal mesosoma, promesonotal suture absent, metanotal groove usually absent, sometimes weakly impressed; mesosoma comparatively stout and high (LMI 38–44). Propodeal spines long to very long, variable in shape from thick and stout to thin and fine, usually straight, rarely weakly curving backwards (PSLI 27–44); propodeal lobes variable, from broadly triangular and comparatively short to elongate triangular and comparatively long, blunt to acute. Petiolar node in profile squamiform and distinctly anteroposteriorly compressed, approximately 2 to 2.4 times higher than long (LPeI 42–50), anterior and posterior faces approximately parallel but anterodorsal margin situated slightly higher than posterodorsal margin, dorsum slightly convex and weakly tapering backwards posteriorly; node in dorsal view 1.5 to 1.7 times wider than long (DPeI 150–168). Postpetiole in profile rounded and weakly anteroposteriorly compressed, approximately 1.2 to 1.6 times higher than long (LPpI 64–84), in dorsal view between 1.1 to 1.4 times wider than long (DPpI 117– 138). Postpetiole in profile more voluminous than petiolar node, in dorsal view approximately 1.2 to 1.4 times wider than petiolar node (PPI 119–137). Mandibles generally distinctly longitudinally rugose, in some series unsculptured and smooth or weakly sculptured; clypeus with well-developed median longitudinal rugula and one or two rugulae at each side; cephalic dorsum between frontal carinae with six to ten longitudinal rugae, most rugae running unbroken to posterior head margin, few rugae interrupted or with cross-meshes; lateral and ventral head with longitudinal rugae, often with cross-meshes. Ground sculpture generally faint, sometimes moderately developed. Mesosoma laterally with irregular longitudinal rugae; mesosomal dorsum longitudinally rugose, rugae often meandering and with cross-meshes, still distinctly longitudinally arranged. Petiolar node and postpetiole usually with weak sculpture laterally and posteriorly while dorsally unsculptured, both often completely unsculptured, and very rarely with distinctly developed and pronounced ground sculpture. Gaster completely unsculptured, smooth and shining. All dorsal surfaces of body with abundant, long, erect or suberect pilosity. Generally, body of brownish colour, often appendages of lighter brown to dark yellow, sometimes mesosoma of darker brown than remaining body.

Notes

Tetramorium steinheili is a very common species in many montane rainforests of eastern Madagascar. The southernmost known locality is Andohahela and the northernmost Bemanevika, but it is also known from Analavelona in the southwest. Interestingly, the distribution is somewhat disjunct since T. steinheili is fairly common in a strip from Andohahela in the south to Ankazobe, Andranomay, and Betampona but is very rare further north, and the next localities are Anjanaharibe and Bemanevika. Together with T. dysalum it has certainly the broadest distribution range within the group, although T. dysalum also occurs in the north of Madagascar and Nosy Be. The altitudinal range of T. steinheili lies from 500 to 1700 m, although it is usually found above 1000 m, and most specimens were collected from leaf litter.

This species displays extraordinary intraspecific variation. While the general body habitus remains very stable, there is remarkable variation in the length and shape of the propodeal spines and the propodeal lobes. The spines are long in all examined material, but they differ in length from one population to another while they are comparatively constant on a local scale. The same is true for the spine shape, since it can vary in thickness and acuteness. Generally, many series from the centre of the distribution range have shorter spines than seen in those from further north or south, although some central series also have very long spines. The propodeal lobes are also fairly variable since they differ from broadly triangular and comparatively short to elongate triangular and comparatively long, and they can be acute or blunted. This variation is relatively stable within populations, and represents a remarkable intraspecific variation since this character is generally highly constant in most Malagasy Tetramorium . Furthermore, some series of T. steinheili , especially from the southeast, have smooth or almost smooth mandibles, whereas most other populations have distinctly striate mandibles. Another interesting variation concerns the sculpture on the petiolar node. It is mostly unsculptured with few rugulae laterally and posteriorly, and generally has a very shiny look. Specimens from Ambohitantely however, have a fine reticulate-punctate to punctate ground sculpture laterally and posteriorly, which gives the node a rough appearance. Also, the colouration can vary from one series to another. Generally, most specimens possess a reddish brown colour with yellowish brown appendages, although there are some series in which the appendages are of the same colour as the remaining body, and other series are darker brown or yellowish brown without any reddish tone.

Since T. steinheili is mostly found in montane rainforests, which are often geographically well separated from each other, it is not surprising to encounter this type of variation. Several populations possess a specific combination of the characters mentioned above that could separate them from most other T. steinheili populations, and we suspect there might be more than one cryptic species hidden within T. steinheili under its current definition. However, we are reluctant to raise such populations to species on the basis of inconsistent differences. One northern series collected from Marojejy, which would have fitted the previous definition of T. steinheili , proved to have some valuable diagnostic characters, and was described as the new species T. yammer . The latter species is generally at the upper size range of T. steinheili , has a weakly wider head (CI 101–103), a very dark brown to black colouration, distinctly smaller eyes (OI 19–20), and very long propodeal spines and propodeal lobes. The examined T. steinheili material was mostly of much lighter colour with larger eyes (OI 21–23). The long spines alone, even in combination with the long propodeal lobes, might be considered comparatively weak evidence to support the naming of a new species, since these characters are quite variable within T. steinheili . However, the character combination of body and eye size, head width, colouration, and lengths of the propodeal spines and propodeal lobes is sufficient to separate the newly described T. yammer fairly well from T. steinheili . As mentioned above, T. steinheili is less common in northeastern Madagascar and not present in Marojejy, but the specimens from Anjanaharibe and Bemanevika proved to be good T. steinheili representatives while being fairly different from T. yammer . For these reasons, we are fairly confident about the separation of T. yammer from T. steinheili .

Tetramorium steinheili is the core species of the group, and not likely to be confused with the remaining eight group members. It differs strikingly from T. ambatovy since the latter species does not have the typical longitudinal rugae on the mesosomal dorsum present in T. steinheili and the other group members. Tetramorium orc , T. macki , and T. robitika all have comparatively short propodeal spines/teeth (PSLI 19–25), whereas the spines of T. steinheili are always long to very long (PSLI 27–44). Tetramorium dysalum is also a widely distributed and common species with a distribution range that even exceeds that of T. steinheili . Both species often occur in the same locality, but are not likely to be confused with each other. The main distinction is surely antennal scape length, which is very short in T. dysalum (SI 64–69) and much longer in T. steinheili (SI 71–76), but both differ also in the shape of the propodeal spines and petiolar node, and usually in mandibular sculpture. The latter is very stable in T. dysalum because the mandibles are always completely unsculptured, very smooth and shining, while they are mostly longitudinally sculptured in T. steinheili . However, as noted above, several series of T. steinheili have unsculptured mandibles, thus rendering this character unreliable. The propodeal spines are usually straight in T. steinheili while they are generally curved backwards in T. dysalum , but this character is also not of universal value since there are exceptions in both species. The petiolar node shape is a good character of high diagnostic value as well. The node of T. dysalum has a very sharply defined anterodorsal margin, which usually contrasts with the less sharply defined margin of T. steinheili .

The remaining species, T. mallenseana , T. sargina , and T. vohitra , are all morphologically comparatively close to T. steinheili , although they can all be well differentiated. Tetramorium mallenseana has a postpetiole that is between 1.6 to 2 times wider than the petiolar node (PPI 167–200) while this relationship is strikingly less pronounced in T. steinheili (PPI 119–137). Also, T. sargina with its decumbent to subdecumbent pilosity on the first gastral tergite differs noticeably from T. steinheili since the gastral pilosity of the latter is erect to suberect. Tetramorium vohitra has a high rounded nodiform petiolar node shape with the antero- and posterodorsal margins at the same height, whereas the node of T. steinheili is squamiform with the anterodorsal margin weakly higher than the posterodorsal, which causes the dorsum to taper backwards posteriorly.

Material examined

MADAGASCAR: no locality data, 1893 (Grandidier); Antananarivo, Andrangoloaka; Antananarivo, 3 km 41° NE Andranomay, 11.5 km 147° SSE Anjozorobe, montane rainforest, 18.47333 S, 47.96 E, 1300 m, 5.– 13.XII.2000 (B.L. Fisher, C. Griswold et al.); Antananarivo, Imerina (Sikora); Antananarivo, Tananarive, Vanjamanitra, 1380 m, 5.XII.1967 (J.-M. Betsch); Antananarivo, Forêt de galerie Andranorovitra, 24.0 km NNE Ankazobe, 18.11243 S, 47.19757 E, 1491 m, disturbed gallery montane forest, 2.–3.VI.2008 (B.L. Fisher et al.); Antananarivo, Forêt de galerie Telomirahavavy, 23.4 km NNE Ankazobe, 18.12167 S, 47.20627 E, 1520 m, disturbed gallery montane forest, 3.–4.VI.2008 (B.L. Fisher et al.); Antananarivo, Réserve Naturelle Sohisika, Sohisika 24.6 km NNE Ankazobe, 18.10322 S, 47.18692 E, 1464 m, 1.–2.VI.2008 (B.L. Fisher et al.); Antananarivo, Réserve Spéciale d'Ambohitantely, Forêt d Ambohitantely, Jardin Botanique, 24.1 km 59° NE Ankazobe, 18.17139 S, 47.28182 E, 1620 m, montane rainforest, 17.–22.IV.2001 (B.L. Fisher, C. Griswold et al.); Antananarivo, Réserve Spéciale d'Ambohitantely, Forêt d Ambohitantely, 20.9 km 72° NE Ankazobe, 18.22528 S, 47.28683 E, 1410 m, montane rainforest, 17.–22.IV.2001 (B.L. Fisher, C. Griswold et al.); Antananarivo, Tsimbazaza, 18.928 S, 47.527 E, 1300 m, park/garden, 16.–19.XII.2006 (B.L. Fisher et al.); Antsiranana, 9.2 km WSW Befingotra, Rés. Anjanaharibe-Sud, 14.75 S, 49.46667 E, 1260 m, montane rainforest, 12.XI.1994 (B.L. Fisher); Antsiranana, 11.0 km WSW Befingotra, Rés. Anjanaharibe-Sud, 14.75 S, 49.45 E, 1550 m, montane rainforest, 18.XI.1994 (B.L. Fisher); Fianarantsoa, 45km S. Ambalavao, 22.21667 S, 47.01667 E, 785 m, rainforest, 24.IX.–1.X.1993 (B.L. Fisher); Fianarantsoa, 43 km S Ambalavao, Rés. Andringitra, 22.23333 S, 47 E, 825 m, rainforest, 10.X.1993 (B.L. Fisher); Fianarantsoa, 40 km S Ambalavao, Rés. Andringitra, 22.21667 S, 46.96667 E, 1275 m, montane rainforest, 14.–19.X.1993 (B.L. Fisher); Fianarantsoa, 38 km S Ambalavao, Rés. Andringitra, 22.2 S, 46.96667 E, 1680 m, montane rainforest, 23.X.1993 (B.L. Fisher); Fianarantsoa, 27.4 km SSW Ambositra, 20.77 S, 47.18667 E, 1600 m, montane rainforest, 15.I.1998 (B.L. Fisher); Fianarantsoa, 28 km SSW Ambositra, 20.76666667 S, 47.18333333 E, 1660 m, montane rainforest, 29.IV.1989 (P.S. Ward); Fianarantsoa, 29 km SSW Ambositra, Ankazomivady, 20.77667 S, 47.165 E, 1700 m, disturbed montane rainforest & montane rainforest, 7.I.1998 (B.L. Fisher); Fianarantsoa, 28 km SSW Ambositra, Ankazomivady, 20.775 S, 47.16833 E, 1670 m, montane rainforest & montane rainforest edge, 14.I.1998 (B.L. Fisher); Fianarantsoa, 2 km W Andrambovato, along river Tatamaly, 21.51167 S, 47.41 E, 1075 m, montane rainforest, 3.–5.VI.2005 (B.L. Fisher et al.); Fianarantsoa, Forêt d'Atsirakambiaty, 7.6 km 285° WNW Itremo, 20.59333 S, 46.56333 E, 1550 m, montane rainforest, 22.–26.I.2003 (B.L. Fisher, C. Griswold et al.); Fianarantsoa, Imerina (Sikora); Fianarantsoa, Miandritsara, 20.79267 S, 47.17567 E, 823 m, rainforest, 23.X.2004 – 19.III.2005 (R. Harin'Hala & M.E. Irwin); Fianarantsoa, Parc National Befotaka-Midongy, Papango 27.7km S Midongy-Sud, Mount Papango, 23.83517 S, 46.96367 E, 940 m, rainforest, 15.XI.2006 (B.L. Fisher et al.); Fianarantsoa, Parc National de Ranomafana, Vatoharanana River, 4.1 km 231° SW Ranomafana, 21.29 S, 47.43333 E, 1100 m, montane rainforest, 27.– 31.III.2003 (B.L. Fisher, C. Griswold et al.); Fianarantsoa, R.S. Ivohibe 8.0 km E Ivohibe, 22.48333 S, 46.96833E, 1200 m, montane rainforest, 15.–21.X.1997 (B.L. Fisher); Fianarantsoa, R.S. Ivohibe 8.0 km E Ivohibe, 22.42167 S, 46.89833 E, 1200 m, montane rainforest, 3.–9.XI.1997 (B.L. Fisher); Fianarantsoa, R.S. Ivohibe, 6.5 km ESE Ivohibe, 22.49667 S, 46.955 E, 1575 m, montane rainforest, 24.X.1997 (B.L. Fisher); Mahajanga, Bemanevika, Souspref. de Bealanana, forest humus (A. Peyrieras); Toamasina, Bevolota 17.1km N Andasibe, 18.77071 S, 48.43164 E, 995 m, montane rainforest, 12.XII.2007 (B.L. Fisher et al.); Toamasina, Forêt Ambatovy, 14.3 km 57° Moramanga, 18.85083 S, 48.32 E, 1075 m, montane rainforest, 21.III.2004 (B.L. Fisher et al.); Toamasina, P.N. Mantadia, 18.79167 S, 48.42667 E, 895 m, rainforest, 25.–28.XI.1998 (H.J. Ratsirarson); Toamasina, Réserve Nationale Intégrale Betampona, Betampona 35.1 km NW Toamasina, 17.91801 S, 49.20074 E, 500 m, 17.XII.2007 (B.L. Fisher et al.); Toliara, Forêt Classée d'Analavelona, 33.2 km 344° NNW Mahaboboka, 22.64333 S, 44.17167 E, 1300 m, montane rainforest, 22.–26.II.2003 (B.L. Fisher, C. Griswold et al.); Toliara, Parc National d'Andohahela, Col du Sedro, 3.8 km 113° ESE Mahamavo, 37.6 km 341° NNW Tolagnaro, 24.76389 S, 46.75167 E, 900 m, montane rainforest, 21.–25.I.2002 (B.L. Fisher, C. Griswold et al.); Toliara, Rés. Andohahela, 13 km NW Enakara, 24.55 S, 46.8 E, 1250 m, montane rainforest, 30.XI.1992 (B.L. Fisher); Toliara, Réserve Spéciale Kalambatritra, Ambinanitelo, 23.4502 S, 46.45658 E, 1325 m, 22.II.2009 (B.L. Fisher et al.); Toliara, Réserve Spéciale Kalambatritra, Ampanihy, 23.4635 S, 46.4631 E, 1270 m, montane rainforest, 9.–10.II.2009 (B.L. Fisher et al.); Toliara, Réserve Spéciale Kalambatritra, Befarara, 23.4178 S, 46.4478 E, 1390 m, montane rainforest, 7.– 8.II.2009 (B.L. Fisher et al.); Toliara, Sakaraha, 22º 54' 41'' S, 44º 41' 42'' E, 760 m, tropical dry forest, 5.II.1983 (P. Rabeson).