Stenamma maximon, 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 : 138-145

Stenamma maximon sp. n. Worker: Figures 115, 116; Queen: Figure 117; Map: Figure 118

Stenamma mgb01 Branstetter, 2012: phylogeny.

Type material.

Holotype worker. GUATEMALA: El Progresso, Cerro Pinalón, 15.08654°N, 89.94445°W ± 50m, 2550m, 30 Apr 2009, cloud forest, ex sifted leaf litter (LLAMA, collection Wa-B-01-2-02) [USNM, specimen CASENT0604875]. Paratypes: same data as holotype but 15.08753°N, 89.94446°W ± 50m, 2550m, 30 Apr 2009 (LLAMA, Wa-B-01-2-38) [1w, CAS, CASENT0623344], [1w, EAPZ, CASENT0623345], [1w, ECOSCE, CASENT0623346], [1w, FMNH, CASENT0623347], [1w, ICN, CASENT0623348], [1w, INBio, CASENT0623349], [1w, JTLC, CASENT0623350], [1w, LACM, CASENT0623351], [1w, MGBPC, CASENT0623352], [1w, MCZ, CASENT0623353], [1w, MZSP, CASENT0623354], [1w, UCD, CASENT0623355], [1w, UNAM, CASENT0623356], [1w, UVGC, CASENT0623357]; 15.08350°N, 89.95319°W ± 55m, 2500m, 2 May 2009 (LLAMA, Wm-B-01-2-02) [1dq, 2w, USNM, CASENT0623358, CASENT0623359, CASENT0623360].

Worker diagnosis.

Integument mostly black, or dark brown to brown; medium-sized species (see HL, ML, PrW below); basal margin of mandible usually sinuous, with a distinct basal depression, but without a basal tooth (rarely basal margin appearing nearly straight); anterior clypeal margin undulating, with 2-4 distinct to somewhat blunt teeth; face sculpture variable, usually mostly smooth and shiny, with, at most, faint carinulae extending to about ¾ the distance to posterior margin of head, but some populations with face mostly rugoreticulate, with only area around posterior margin becoming smooth; pronotum sculpture variable, usually mostly smooth and shiny, but sometimes with some longitudinal rugulae on humeri, remainder of mesosoma with rugulae and punctae; postpetiole bulging, appearing distinctly larger than petiolar node (PPH/PH 0.96-1.14; PW/PPW 0.65-0.78); eye of moderate size (EL 0.11-0.16, REL 16-22), oval-shaped, with 6-8 ommatidia at greatest diameter (rarely 9 or 10); propodeal spines usually tuberculate, or at least forming a sharp angle, but sometimes forming a blunt angle, or becoming more developed, short (PSL 0.07-0.12, PSI 1.0-2.0). Similar species: Stenamma crypticum , Stenamma huachucanum , Stenamma ochrocnemis .

Geographic range.

Southern Mexico to Honduras.

Worker description.

(23 measured) HL 0.67-0.86 (0.79), HW 0.57-0.76 (0.68), FLD 0.16-0.21 (0.19), PCW 0.02-0.0.05 (0.04), SL 0.53-0.74 (0.68), EL 0.11-0.16 (0.12), ACL 0.49-0.65 (0.59), ML 0.84-1.09 (1.02), PrW 0.39-0.50 (0.46), PSL 0.07-0.12, SDL 0.06-0.09, PL 0.29-0.38 (0.37), PH 0.19-0.24 (0.23), PW 0.15-0.19 (0.18), PPL 0.21-0.27 (0.24), PPH 0.20-0.25 (0.25), PPW 0.22-0.27 (0.26), MFL 0.57-0.82 (0.76), MTL 0.48-0.65 (0.61), CI 83-93 (85), SI 80-101 (100), REL 16-22 (18), FLI 25-30 (28), PSI 1.0-2.0 (1.1), MFI 89-108 (89), ACI1 66-70 (68), ACI2 85-96 (88).

Medium-sized species; general body color mostly black, or dark brown to brown, with appendages dark brown to orange-brown, lighter at joints and toward extremities; setae golden brown; mandible with 6-8 teeth (usually 7), consisting of 3 distinct apical teeth, a basal tooth, and 2-4 smaller teeth/denticles, which are often worn and indistinct; basal margin of mandible usually sinuous, with a distinct basal depression, but without a basal tooth, sometimes basal margin only slightly sinuous or nearly straight; mandible often mostly smooth and shiny, with scattered piligerous punctae and some striations (type population), but sometimes surface completely carinulate, with carinulae extending from base to near teeth; anterior clypeal margin forming 2-4 distinct to somewhat blunt teeth, outer teeth often larger and sharper than inner teeth (best viewed in anterodorsal view); median clypeal lobe with a pair of faint longitudinal carinulae, apex of lobe with a short transverse carinula, remainder of clypeus mostly smooth and shiny; area in between median lobe of clypeus and anterior clypeal margin forming a distinct cavity where mandibles insert; posterior extension of clypeus between antennal insertions of moderate width (PCW 0.02-0.0.05), with sides subparallel to slightly hour-glass-shaped; frontal lobes of moderate width (FLD 0.16-0.21, FLI 25-30), not greatly covering torular lobes in full-face view; head roughly oval-shaped (CI 83-93), with posterior margin flat to slightly depressed mesad; face sculpture variable, usually mostly smooth and shiny (type population), with, at most, faint carinulae extending to about ¾ the distance to posterior margin of head, but some populations with face mostly rugoreticulate, with only area around posterior margin becoming smooth; scape of moderate length (SI 80-101), reaching posterior margin of head when laid back; scape surface mostly smooth and shiny, with scattered piligerous punctae; flagellum with a distinct 4-segmented antennal club; pronotum and mesonotal dorsum sculpture variable, usually mostly smooth and shiny, but sometimes with longitudinal rugulae on humeri, remainder of mesosoma mostly sculptured (contrast between smooth pronotum, and sculptured mesonotum, mesopleuron, and propodeum distinctive); mesopleuron mostly punctate, with a few rugulae; side of propodeum with rugulae and some faint punctae; dorsum and declivity of propodeum with variable number of transverse carinulae; promesonotum in profile low-domed, and roughly symmetrical, but anterior declivity sometimes more sharply angled than posterior face (type population); metanotal groove in profile well-demarcated, anterior slope often smoothly transitioning with promesonotum; propodeal spines usually tuberculate (type population), or at least forming sharp angles, but sometimes forming blunt angles, or more developed and short (PSL 0.07-0.12, PSI 1.0-2.0); petiole of moderate length (PL/HW 0.46-0.56), with peduncle thick, often with anteroventral edge sharp; petiolar node in profile somewhat small (PH/PL 0.58-0.68), wedge-shaped, with anterior face longer and more sloping than almost vertical posterior face, dorsum of node rounded, and distinctly pointed posteriad; postpetiole bulging, globular, appearing distinctly larger than petiolar node (PPH/PH 0.96-1.14; PW/PPW 0.65-0.78), anterior face of node much longer than posterior face; petiolar and postpetiolar nodes mostly smooth and shiny, remaining waist surfaces punctate, with a few rugulae around bases of nodes; gaster smooth and shiny, with scattered piligerous punctae; pilosity on face short, with a layer of sparse suberect setae, and a denser layer of decumbent setae, remainder of body dorsum with longer standing pilosity; pilosity on gastral dorsum usually distinctly bilayered, with a layer of longer suberect to subde cumbent setae, and a layer of shorter decumbent setae, both layers similar in density; setae on scape and legs mostly decumbent to appressed, with some longer suberect setae on femoral venters and coxae.

Queen description.

(10 measured) HL 0.73-0.84 (0.84), HW 0.67-0.76 (0.76), FLD 0.19-0.23 (0.23), PCW 0.03-0.06 (0.06), SL 0.57-0.71 (0.71), EL 0.19-0.22 (0.22), ACL 0.47-0.62 (0.62), ML 1.05-1.34 (1.34), PrW 0.56-0.74 (0.74), PSL 0.13-0.17 (0.14), SDL 0.09-0.10 (0.10), PL 0.37-0.47 (0.47), PH 0.23-0.27 (0.27), PW 0.19-0.22 (0.22), PPL 0.20-0.29 (0.27), PPH 0.24-0.30 (0.30), PPW 0.27-0.33 (0.33), MFL 0.63-0.84 (0.84), MTL 0.55-0.70 (0.70), CI 91-93 (91), SI 82-94 (94), REL 26-30 (29), FLI 27-30 (30), PSI 1.4-1.7 (1.4), MFI 90-108 (90), ACI1 64-68 (65), ACI2 76-93 (87).

Same as worker except for standard queen modifications and as follows (comparison between worker and queen of type population form only): facial sculpture usually more developed (carinulae/rugulae longer and more distinct); mesopleuron mostly smooth and shiny; propodeum with transverse carinulae that wrap around entire surface; lower layer of gastral setae more dense, almost pubescent; propodeal spines (compared to worker from same population) slightly longer, more developed (PSL 0.13-0.17, PSI 1.4-1.7).

Male.

Unknown.

Biology.

Stenamma maximon is an inhabitant of high elevation wet forest habitats (e.g. cloud forest, wet oak forest, hardwood forest, wet oak-pine forest), ranging from approximately 1700-2800 m elevation. When present, Stenamma maximon workers are one of the most common components of the leaf-litter microenvironment, with most collections of the species made by sifting leaf litter from the forest floor. It has been collected also fairly commonly at cookie baits, suggesting that workers do forage epigeically some of the time. This is not surprising since Stenamma maximon is a larger species of Stenamma . I have found only one nest of Stenamma maximon , which was in a small log in leaf litter. A few stray workers have been collected also from underneath a rock. Given these observations, I would guess that Stenamma maximon nests in wood in the leaf litter and forages both within the leaf litter and sometimes above it.

Comments.

The presence of a bulging postpetiole, a sinuous basal margin of the mandible, and a toothed anterior clypeal margin, makes Stenamma maximon easily separable from most other Stenamma species. However, Stenamma maximon forms a complex of phenotypic variants (described below) and some populations lose the distinctiveness of the type population form and are more difficult to separate from similar species.

Distinctive features of the type population form (Figures 115, 116) are indicated in the species description (see parenthetical comments). Most notable are the characters mentioned in the previous paragraph, combined with a mostly smooth head and promesonotum. This form occurs mainly at high elevation sites in Chiapas, Mexico, and throughout most of Guatemala. It co-occurs with variant 1 at several sites in Guatemala.

Variant 1 (Figure 116 A–C) includes many populations in Guatemala and Honduras. Each is variable and some are intermediate in morphology between variant 1 and the type form. Variant 1 differs from the type form as follows: basal margin of mandible only slightly sinuous, without a distinct basal depression; teeth of anterior clypeal margin reduced, sometimes only two blunt middle teeth or undulations perceptible; face strongly sculptured with rugoreticulae and carinulae, only sometimes posterior ¼ of head smooth; lateral margins of promesonotal dorsum with distinctive oblique carinulae/rugulae that cross from upper portion of pronotal side to dorsum, middle of promesonotum smooth; propodeal spines reduced to blunt angles. I have found variant 1 with the type form most often at the locality 5km SE Antigua in Guatemala. Figure 116 A–F shows two specimens from this locality, with D–F corresponding to the type form. This sympatry suggests that the two forms are somewhat reproductively isolated from one another. I have not separated variant 1 as a distinct species, however, because some populations, especially in Honduras, appear intermediate in phenotype. The general pattern I see is that the type form occurs in Chiapas, Mexico, to Guate mala; variant 1 occurs in Guatemala, often in sympatry with the type form; and then populations in Honduras appear intermediate. I also see some similarity between variant 1 and certain populations of Stenamma crypticum , perhaps indicating that these two species occasionally hybridize.

Variant 2 (Figure 116 G–I) is known from a few collections made from the wet side of the Sierra Juarez Mountains in Oaxaca, Mexico. These specimens are larger than average, have short propodeal spines (longer than in type form), and have lighter brown-black body coloration.

Variant 3 (Figure 116 J–L) is known from a single collection at 4.6km S Suchixtepec in Oaxaca, Mexico. It is similar to variant 2, except that the basal margin of the mandible is nearly straight and the anterior clypeal margin appears as a median emargination, without teeth. It is possible this variant is not conspecific with Stenamma maximon , but has evolved similar features due to convergence. I have not been able to test this hypothesis with molecular data, but it should be done.

Material examined.

EL SALVADOR: Santa Ana: Cerro Verde, [ca. 13.827°N, 86.631°W], 1760m, 14 May 1971 (S. B. Peck); GUATEMALA: Chimaltenango: Finca Chincharas, Rincón Suizo, 14.79775°N, 90.98380°N, 2490m, 17 Sep 2008 (R. S. Anderson); 3.8km NNE Tecpán, 14.7969°N, 90.9817°W, 2500m, 17 Sep 2008 (M. G. Branstetter);El Progresso: Cerro Pinalón, 15.08654°N, 89.94445°W, 2550m, 30 Apr 2009 (M. G. Branstetter); Guatemala: nr Las Nubes, 14.53975°N, 90.34882°W, 2050m, 18 Sep 2008 (R. S. Anderson); 7km ESE San José Pinula, 14.5392°N, 90.3493°W, 2060m, 18 Sep 2008 (M. G. Branstetter); Jalapa: Aldea Manzano, 1.8km WNW San José La Sierra, 14.5048°N, 90.2561°W, 1990m, 18 Sep 2008 (M. G. Branstetter); El Manzano, 14.50476°N, 90.25613°W, 2150m, 18 Sep 2008 (R. S. Anderson); 4km E Mataquescuintla, 14.53329°N, 90.15314°W, 2400m, 1 Jun 2009 (LLAMA); 4km E Mataquescuintla, 14.52952°N, 90.14806°W, 2600m, 1 Jun 2009 (LLAMA);5km ENE Mataquescuintla, 14.5336°N, 90.1432°W, 255 0m, 5 Jul 2007 (J. L. Cozar); Huehuetenango: above Bojonal, 15.53697°N, 91.98158°W, 2350m, 16 Sep 2008 (R. S. Anderson); 3.3km WSW El Paraíso, 15.5370°N, 91.9816°W, 2350m, 16 Sep 2008 (M. G. Branstetter); San Miguel Chicharro, 4km NNW El Paraíso, 15.5796°N, 91.9692°W, 2100m, 16 Sep 2008 (L. Sáenz); Quetzaltenango: Fuentes Georginas, 5.1km SW Santa Maria, 14.7489°N, 91.4806°W, 2500m, 13 Sep 2008 (M. G. Branstetter);12km SE Zunil, NW face Cerro Zunil, [ca. 14.7488°N, 91.4800°N,], 2700m, 28 May 1991 (R. S. Anderson); 12km SE Zunil, Fuentes Georginas, [ca. 14.7488°N, 91.4800°W], 2460m, 27 May 1991 (R. S. Anderson); Quiché: Laguna Danta, 15.42729°N, 90.81689°W, 2300m, 15 Sep 2008 (R. S. Anderson); 5.1km SE Los Encuentros, 14.83598°N, 91.10867°W, 2660m, 17 Sep 2008 (L. Sáenz); 10km E Los Encuentros, 14.83598°N, 91.10867°W, 2620m, 17 Sep 2008 (R. S. Anderson); 1.4km SW Macalajau, 15.4056°N, 90.8381°W, 2360m, 15 Sep 2008 (M. G. Branstetter); 3km S Joya Larga, 15.40538°N, 90.83805°W, 2350m, 15 Sep 2008 (R. S. Anderson); Sacatepéquez: 5km SE Antigua, 14.53651°N, 90.69480°W, 2150m, 10 Jun 2009 (LLAMA); 5km SE Antigua, 14.52848°N, 90.68884°W, 2350m, 10 Jun 2009 (LLAMA);5km SE Antigua, 14.52357°N, 90.68800°W, 2470m, 11 Jun 2009 (LLAMA); Cerro Alux, 14.61053°N, 90.64191°W, 2190m, 9 Sep 2008 (R. S. Anderson); Cerro Carmona, 6km SE Antigua, 14.5345°N, 90.6945°W, 2180m, 9 Sep 2008 (L. Sáenz); Guatemala City, Cerro Alux, [ca. 14.6167°N, 90.6333°W], 2260m, 9 Jun 1991 (R. S. Anderson); San Marcos: 5.3km WSW San Marcos, 14.9635°N, 91.8314°W, 2520m, 11 Sep 2008 (M. G. Branstetter); Zacapa: 14km NNE Teculután, 15.1144°N, 89.6805°W, 2270m, 6 Jul 2007 (M. G. Branstetter) HONDURAS:Comayagua: 10km E Comayagua, 14.45976°N, 87.54591°W, 2000m, 15 May 2010 (LLAMA); 12km ENE Comayagua, 14.48045°N, 87.53238°W, 2140m, 15 May 2010 (M. G. Branstetter); 18km ENE Comayagua, [ca. 14.456°N, 87.541°W], 17 Jun 1994 (S. & J. Peck);Francisco Morazán: PN La Tigra, 3.6km SW San Juancito, 14.2073°N, 87.0943°W, 25 Sep 2008 (M. G. Branstetter); 23 km N Tegucigalpa, PN La Tigre, Esperanza Trail, [ca. 14.181°N, 87.090°W], 15 Jul 1994 (S. B. Peck); Reserva Uyuca, 4.8km WNW Zamorano, 14.02695°N, 87.07077°W, 1900m, 24 Sep 2008 (M. G. Branstetter);Lempira: PN Celaque, 8.7km SW Graçias, 14.5588°N, 88.6612°W, 2100m, 30 Sep 2008 (M. G. Branstetter); Ocotepeque: 13km E Nueva Ocotepeque, 14.42478°N, 89.0606°W, 2140m, 26 May 2010 (LLAMA); 13km E Nueva Ocotopeque, 14.45697°N, 89.06849°W, 2200m, 25 May 2010 (LLAMA); 13km E Nueva Ocotopeque, 14.41807°N, 89.06915°W, 2210m, 26 May 2010 (LLAMA); MÉXICO:Chiapas: Cerro Huitepec (Pico), ca. 5km W San Cristobal, [ca. 16.7500°N, 92.6802°W], 2750m, 18 Sep 1991 (R. S. Anderson); Cerro de Tapalapa, 17.18786°N, 93.12308°W, 2260m, 28 May 2008 (R. S. Anderson); 5km NE Coapilla, 17.17602°N, 93.13293°W, 1990m, 26 May 2008 (M. G. Branstetter); 7.3km NE Coapilla, 17.1826°N, 93.1182°W, 2200m, 12 Jul 2007 (M. G. Branstetter); Huitepec, S. Cristóbal, 16.75018°N, 92.68331°W, 2480m, 29 May 2008 (LLAMA); 7.4km SSW Montozintla de Mendoza, [ca. 15.3049°N, 92.2597°W], 2000m, 17 Sep 1992 (R. S. Anderson); Reserva Huitepec, 16.7448°N, 92.6885°W, 2600m, 11 Jul 2007 (J. Longino); 5km W San Cristobal, Cerro Huitepec, 16.75000°N, 92.68023°W, 2700m, 14 Sep 1992 (R. S. Anderson); 15km E San Cristóbal, 16.74713°N, 92.49002°W, 2500m, 29 May 2008 (LLAMA); 4km N Union Juarez, Volcan Tacana, lower slopes, [ca. 15.333°N, 92.100°W], 2000m, 20 Sep 1992 (R. S. Anderson); Oaxaca: 5.1km S Suchixtepec, [ca. 16.0833°N, 96.4667°W], 2150m, 25 Jul 1992 (R. S. Anderson); 27km SW Valle Nacional, 17.59582°N, 96.47572°W, 2290m, 11 Aug 2009 (M. G. Branstetter).