Stenamma brujita, Branstetter, Michael G., 2013

Branstetter, Michael G., 2013, Revision of the Middle American clade of the ant genus Stenamma Westwood (Hymenoptera, Formicidae, Myrmicinae), ZooKeys 295, pp. 1-277 : 39-45

Stenamma brujita sp. n. Worker: Figures 54, 55; Queen: Figure 56; Map: Figure 57

Stenamma mgb05 [variant 3 below] Branstetter, 2012: phylogeny.

Type material.

Holotype worker. GUATEMALA, Zacapa: 2km SE La Unión, 14.94706°N, 89.27660°W ± 50m, 1550m, 12 May 2009, cloud forest, ex sifted leaf litter (LLAMA, collection Wa-B-03-1-32) [USNM, specimen CASENT0604945]. Paratypes: same data as holotype but 14.94460°N, 89.27726°W ± 57m, 1550m, 12 May 2009 (LLAMA, Wm-B-03-1-04), [1w, CAS, CASENT0623248], [1w, EAPZ, CASENT0623249], [1w, ECOSCE, CASENT0623250], [1w, FMNH, CASENT0623251], [1w, ICN, CASENT0623252, [1w, INBio, CASENT0623253], [1w, JTLC, CASENT0623527], [1w, LACM, CASENT0623254], [2w, MGBPC, CASENT0623528, CASENT0623529], [1w, MCZ, CASENT0623255], [1w, MZSP, CASENT0623256, [1w, UCD, CASENT0623257], [1w, UNAM, CASENT0623258], [1dq, 1w, USNM, CASENT0606239, CASENT0606656], [1w, UVGC, CASENT0623259].

Worker diagnosis.

Integument mostly black, red-black, or brown; medium to large-sized species (see HL, ML, PrW below); head and mesosoma foveate to coarsely rugoreticulate; eye relatively small (EL 0.09-0.13, REL 10-14), circular, and slightly bulging, with 5-7 ommatidia at greatest diameter; pilosity on gastral dorsum long, dense and mostly suberect; propodeal spines tuberculate to long and robust, usually of moderate length (PSL 0.15-0.37, PSI 1.3-2.9); anterior clypeal margin forming a single shallow to deep median emargination, or rarely, 4 blunt teeth; basal margin of mandible straight to sinuous, sometimes with a broad basal depression, but without a distinct notch or tooth; 4-segmented antennal club indistinct. Similar species: Stenamma zelum .

Geographic range.

Mexico (Atlantic slope) to Honduras.

Worker description.

(21 measured) HL 0.90-1.20 (1.05), HW 0.77-1.15 (1.00), FLD 0.21-0.32 (0.29), PCW 0.04-0.07 (0.06), SL 0.75-1.01 (0.93), EL 0.09-0.13 (0.12), ACL 0.63-0.78 (0.72), ML 1.15-1.62 (1.45), PrW 0.52-0.78 (0.70), PSL 0.15-0.37, SDL 0.08-0.16, PL 0.45-0.64 (0.56), PH 0.21-0.35 (0.27), PW 0.15-0.24 (0.21), PPL 0.21-0.31 (0.26), PPH 0.18-0.28 (0.24), PPW 0.20-0.30 (0.27), MFL 0.81-1.25 (1.10), MTL 0.66-0.95 (0.88), CI 85-96 (96), SI 85-99 (88), REL 10-14 (12), FLI 25-31 (29), PSI 1.3-2.9 (2.3), MFI 86-105 (91), ACI1 62-65 (64), ACI2 78-89 (82).

Medium to large-sized species; general body color usually red-black (type population) to black, with patches of brown, but some populations more uniformly brown; mandibles and appendages always lighter than body, brown to orange-brown; setae golden brown; mandible with 4-8 teeth (usually 7), consisting of 3-4 distinct apical teeth, a basal tooth, and a variable number of inner teeth, which are often worn and indistinct; basal tooth usually of moderate size (type population), but sometimes more robust and projecting; basal margin of mandible straight to slightly sinuous, sometimes with a shallow, broad basal depression, but without a distinct notch or tooth; mandible mostly smooth and shining, with scattered piligerous punctae and a few lateral striae; median lobe of clypeus usually slightly produced and clearly visible in full-face view (type population), but sometimes becoming obliquely flattened and angled more dorsoventrally, making it less visible; anterior clypeal margin varying from having a shallow to deep median emargination (type population), to forming 4 distinct blunt teeth; median lobe usually with a pair of faint longitudinal carinulae that diverge toward anterior margin, apex of lobe with a faint to strong transverse carinula; posterior extension of clypeus between frontal lobes of relatively moderate width (PCW 0.04-0.07), with sides subparallel to hour-glass-shaped; frontal lobes average to slightly expanded outward (FLD 0.21-0.32, FLI 25-31), with underlying torular lobes always visible in full-face view; head in full-face view roughly oval shaped to subcircular (CI 85-97), with posterior margin slightly to distinctly depressed medially; eyes relatively small (EL 0.09-0.13, REL 10-14), circular, and somewhat bulging, with 5-7 ommatidia at greatest diameter; head foveate to coarsely rugoreticulate, shiny, often with a few short costae extending back from frontal lobes, interstices with piligerous punctae; scape relatively short, not reaching posterior margin of head when laid back (SI 85-99); scape shiny, usually with only scattered piligerous punctae (type population), but sometimes more robust, with punctae deeper and broader, becoming foveolae; flagellum with indistinct 4-segmented antennal club; mesosoma robust, foveate to coarsely rugoreticulate, with foveae most prominent on promesonotal dorsum; propodeal spines varying from short tubercles to long robust spines (PSL 0.15-0.37, PSI 1.3-2.9), which are usually spiniform and project dorsoposteriorly (type population), but sometimes form robust vertical pointing triangles; promesonotum in profile varying from being domed and nearly symmetrical (type population), to domed and asymmetrical, with apex occurring anterior of midpoint, to high-domed and asymmetrical; humeral angles rounded and indistinct, to becoming produced and angulate (type population), the latter occurring when the promesonotal side is scalloped slightly inward; metanotal grove present, but variable in depth and degree of distinctness; anterodorsal margin of propodeum in profile flat to distinctly raised into a welt (type population); propodeal declivity with a variable number of transverse carinae, often mostly smooth and shiny; petiole shape in profile usually appearing relatively long and somewhat gracile (PL/HW 0.53-0.63), with a small distinct node (PH/PL 0.45-0.55) (type population), but sometimes petiole is more robust and strongly wedge-shaped, without a clear distinction between the node and peduncle; postpetiole in profile usually low-domed, nearly symmetrical, and appearing as high or slightly smaller than petiolar node (type population), but sometimes postpetiole distinctly larger than petiolar node; postpetiole in dorsal view elongate, and reaching its widest point near pos terior margin; waist sculpture variable, nodes usually mostly smooth and shiny, but sometimes more punctate and/or with longitudinal costae or rugulae, ventral surface punctate, dorsal surface of peduncle punctate and with a variable number of rugulae; gaster mostly smooth and shiny, with scattered piligerous punctae, and short furrows on anterior constriction where gaster inserts into postpetiole; most of body with relatively long standing pilosity; scape either with a single layer of mostly decumbent setae, or bilayered with a sparse layer of longer suberect setae over a denser decumbent layer (type population); gastral pilosity relatively long and somewhat dense, with most setae suberect to subdecumbent; setae on legs suberect to decumbent, with some populations having predominately suberect setae (type population) and others mainly decumbent setae, longer suberect setae always present on femoral venters and coxae.

Queen description.

(5 measured) HL 0.96-1.03 (1.03), HW 0.91-0.99 (0.99), FLD 0.26-0.29 (0.29), PCW 0.05-0.07 (0.06), SL 0.84-0.89 (0.89), EL 0.17-0.19 (0.17) ACL 0.68-0.72 (0.71), ML 1.47-1.57 (1.57), PrW 0.76-0.82 (0.82), PSL 0.18-0.28 (0.28), SDL 0.13-0.16 (0.13), PL 0.59-0.61 (0.60), PH 0.28-0.32 (0.31), PW 0.22-0.25 (0.24), PPL 0.27-0.33 (0.32), PPH 0.23-0.28 (0.28), PPW 0.25-0.31 (0.29), MFL 1.01-1.06 (1.06), MTL 0.79-0.85 (0.85), CI 93-97 (97), SI 86-94 (90), REL 17-20 (17), FLI 28-31 (29), PSI 1.1-2.1 (2.1), MFI 87-95 (93), ACI1 63-64 (63), ACI2 80-85 (80).

Same as worker except for standard queen modifications and the following: Propodeal spines less variable (PSL 0.18-0.28, PSI 1.1-2.1), usually present, of moderate length, and thick at base (only Nahá population with spines tuberculate); setae on scape less variable, usually with a sparse layer of longer suberect setae and a layer of denser decumbent setae (only Nahá population with setae uniformly subdecumbent); wing venation as in Figure 56D.

Male.

Unknown.

Biology.

Stenamma brujita is known only from Winkler and Berlese samples of leaf litter collected from the floor of wet forest habitats (e.g. lowland rainforest, montane wet forest, cloud forest, pine cloud forest, oak-pine forest). The species has a broad elevational range, occurring from 200-1800 m, but it is most common at mid-elevations (1000-1500 m).

Comments.

The combination of large size, small eyes, and foveate sculpture make Stenamma brujita a very distinctive species, unlikely to be confused with any other MAC species. However, Stenamma zelum , which is not closely related to Stenamma brujita ( Branstetter 2012), has converged on a similar phenotype and may cause problems with identification. Fortunately, these two species are geographically isolated from one another, with Stenamma brujita reaching only as far south as northwestern Honduras, and Stenamma zelum extending only as far north as northeastern Honduras. Using morphology, Stenamma brujita can be distinguished from Stenamma zelum by its more rounded head (rectangular in Stenamma zelum ), longer propodeal spines (PSI 1.3-2.9 vs. 1.0-1.3), and lower FLI (27-31 vs. 31-34). In addition, the anterior clypeal margin forms four sharp teeth in Stenamma zelum , with the outer teeth usually strongly projecting. In contrast, most populations of Stenamma brujita have the anterior clypeal margin forming a single median emargination (all Honduras populations like this), and in those specimens that do have clypeal teeth, the teeth are all blunt.

Stenamma brujita is quite variable throughout its range and may comprise a complex of several species. I choose to identify a single species here, because every population exhibits some amount of variation, none of the variants occur in sympatry, and some populations have intermediate phenotypes. I do however, identify three main variants that differ significantly from the holotype population.

Variant 1 (Figure 54 A–C) includes all collections from Tamaulipas and Hidalgo, Mexico. It has the following features: body sculpture more rugoreticulate than foveate; propodeal spines long, straight and more slender; petiole with a distinct concavity below node.

Variant 2 (Figure 55 D–F), the most distinctive variant, is known from a few collections taken on the wet Atlantic slope of the Sierra Juarez, between Oaxaca and Valle Nacional in Mexico. It has the following features: body very large; general body color very dark, mostly black; petiole wedge-shaped, usually without a distinct node; propodeal spines forming robust, blunt-tipped triangles, which point almost vertically.

Variant 3 (Figure 56 G–I) occurs at several localities in Chiapas, México, mainly Nahá and Lago Metzabok. It is characterized by the following: general body color brown; promesonotum in profile high-domed, and asymmetrical; propodeal spines tu berculate; petiole in profile appearing more gracile with node reduced in size; anterior clypeal margin forming 4 blunt teeth.

Some additional populations in Chiapas, Mexico, and all of the populations in Guatemala and Honduras, are most similar to the holotype population (La Unión, Guatemala). However, there is considerable variation among populations and some have character states that are intermediate between the holotype form and the different variants just described. Specimens from higher elevations tend to be larger, darker and more robust. The specimens from Purulhá, Guatemala appear especially robust-looking, with very long, sinuous propodeal spines and coarser sculpturing. Interestingly, these specimens have the petiolar node more wedge-shaped, similar to variant 2. Key character states of the holotype population are indicated in the worker description.

Material examined.

GUATEMALA:Baja Verapaz: 7.3km E Purulhá, [ca. 15.267°N, 90.132°W], 1700m, 19 May 1991 (R. S. Anderson); Suchitepéquez: Finca Sn. Jerónimo, 14.55914°N, 91.16705°W, 1790m, 11 Dec 2010 (L. Sáenz); Volcán Atitlán, 10km SE Santiago Atitlán, 14.552°N, 91.193°W, 1690m, 10 Sep 2008 (M. G. Branstetter); 4km S Vol. Atitlán, 14.55195°N, 91.192333°W, 1750m, 15 Jun 2009 (LLAMA); Zacapa: 2km SE La Unión, 14.94706°N, 89.27660°W, 1550m, 12 May 2009 (LLAMA); 2km SE La Unión, 14.95463°N, 89.27721°W, 1430m, 12 May 2009 (LLAMA); 3.5km SE La Union, 14.95000°N, 89.26667°W, 1500m, 6 Jun 1991 (R. S. Anderson); HONDURAS: Cortés: Parque Nacional Cusuco, 15.48710 °N, 88.23469°W, 1330m, 30 May 2010 (LLAMA); Parque Nacional Cusuco, 15.48940°N, 88.23584°W, 1290m, 30 May 2010 (LLAMA); 25km N Cofradia, PN Cusuco, [ca. 15.497°N, 88.227°W], 1550m, 26 Aug 1994 (S. & J. Peck); MÉXICO: Chiapas: 10km W El Bosque, [ca. 17.0440°N, 92.8612°W], 1475m, 15 Sep 1992 (R. S. Anderson); 10.6km W El Bosque, [ca. 17.043°N, 92.762°W], 1460m, 25-29 Aug 1973 (A. F. Newton); Lago Metzabok, 17.12562°N, 91.63086°W, 570m, 6 Jun 2008 (LLAMA); Nahá, 16.96358°N, 91.59332°W, 985m, 8 Jun 2008 (LLAMA); Nahá, 16.94864°N, 91.59383°W, 930m, 8 Jun 2008 (LLAMA); 12.5km NW Ocosingo, [ca. 16.983°N, 92.183°W], 1400m, 16 Sep 1992 (R. S. Anderson); 19km NW Ocozocoautla, [ca. 16.877°N, 93.458°W], 975m, 4-5 Sep 1973 (A. F. Newton); Hidalgo: 11km SW Chapulhuacán, [ca. 21.147°N, 98.966°W], 1200m, 5 Jul 1976 (A. F. Newton; Oaxaca: 10km S Valle Nacional, [ca. 17.724°N, 96.324°W], 650m, 19 May 1971 (S. B. Peck); 13.2km SW Valle Nacional, 17.65934°N, 96.33426°W, 1360m, 11 Aug 2009 (M. G. Branstetter); 25km S Valle Nacional, [ca. 17.670°N, 96.330°W], 1200m, 21 May 1971 (S. B. Peck); 26km S Valle Nacional, km 71, [ca. 17.645°N, 96.336°W], 1220m, 25 Jun 1983 (S. & J. Peck); Puebla: 24km N Xicotepec de Juarez, [ca. 20.282°N, 97.963°W], 1070m, 17 Jun 1983 (R. S. Anderson); Tamaulipas: El Cielo, nr Alta Cima, 23.06518°N, 99.20433°W, 980m, 21 Aug 2009 (L. Sáenz); 1.8km W Alta Cima, 23.06110°N, 99.21564°W, 1340m, 23 Aug 2009 (M. G. Branstetter); nr Gomez Farias Rancho del Cielo, [ca. 23.063°N, 99.205°W], 1000m, 7 Aug 1983 (S. & J. Peck) Veracruz: Los Tuxtlas, 10km NNW Sontecomapan, 18.583°N, 95.083°W, 200m, 20 Mar 1985 (P. S. Ward); Los Tuxtlas, 10km NNW Sontecomapan, 18.583°N, 95.083°W, 500m, 21 Mar 1985 (P. S. Ward).