Stenamma saenzae, 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 : 184-190

Stenamma saenzae sp. n. Worker: Figures 146, 147; Queen:Figure 148; Map: Figure 149

Type material.

Holotype worker. MÉXICO, Chiapas: 5km NE Coapilla, 17.17550°N, 93.13212°W, 1990m, 25 May 2008, 2° mesophyll forest, ex sifted leaf litter (LLAMA, collection Wa-A-04-1-26) [USNM, specimen CASENT0603860]. Paratypes: same data as holotype but 17.18330°N, 93.15209°W ± 50m, 1915m, 25 May 2008 (LLAMA, Wa-A-04-2-07) [1dq, 1w, CAS, CASENT0623473, CASENT0623474], [1w, EAPZ, CASENT0623475], [1w, ECOSCE, CASENT0623476], [1w, FMNH, CASENT 0623477], [1w, ICN, CASENT0623478]; 17.17550°N, 93.13212°W ± 50m, 1990m, 25 May 2008 (LLAMA, Wa-A-04-2-06) [1w, INBio, CASENT0623469], [1w, JTLC, CASENT0623470], [1w, LACM, CASENT0623471], [1w, MGBPC, CASENT0623472]; 17.18296°N, 93.15197°W ± 50m, 1915m, 25 May 2008 (LLAMA, Wa-A-04-2-15) [1dq, 1w, MCZ, CASENT0623479, CASENT0623480], [1w, MZSP, CASENT0623481], [1w, UCD, CASENT0623482], [1w, UNAM, CASENT0623483], [1w, UVGC, CASENT0623484], [1w, USNM, CASENT0623485]; 17.18273°N, 93.15184°W ± 50m, 1915m, 25 May 2008 (LLAMA, Wa-A-04-2-21) [1dq, USNM, CASENT0603866]

Worker diagnosis.

Integument mostly brown to orange-brown and mottled; small-sized species (see HL, ML, PrW below); basal margin of mandible sinuous, always with a basal notch containing a small tooth; anterior clypeal margin undulating, often forming 4 blunt teeth; face completely sculptured, usually mostly rugoreticulate; gastral pilosity with a dense layer of short decumbent to appressed setae, and a sparse layer of longer suberect setae; eye small (EL 0.05-0.09, REL 10-16), subcircular, with 3-5 ommatidia at greatest diameter; posterior extension of clypeus between antennal insertions narrow (PCW 0.01-0.02), with inner margins of frontal lobes almost touching anteriorly; scape short (SI 81-92), not reaching posterior margin of head when laid back; propodeal spines tuberculate to short (PSL 0.07-0.14, PSI 1.5-2.3). Similar species: Stenamma crypticum , Stenamma excisum , Stenamma nanozoi .

Geographic range.

Southern Mexico to Honduras.

Worker description.

(16 measured) HL 0.52-0.69 (0.65), HW 0.43-0.59 (0.54), FLD 0.11-0.14 (0.14), PCW 0.01-0.02 (0.02), SL 0.36-0.50 (0.50), EL 0.05-0.09 (0.07), ACL 0.37-0.49 (0.47), ML 0.60-0.82 (0.77), PrW 0.30-0.41 (0.38), PSL 0.07-0.14 (0.10), SDL 0.04-0.07 (0.06), PL 0.23-0.31 (0.29), PH 0.14-0.18 (0.17), PW 0.11-0.14 (0.14), PPL 0.12-0.19 (0.16), PPH 0.12-0.17 (0.17), PPW 0.14-0.19 (0.17), MFL 0.39-0.53 (0.51), MTL 0.32-0.44 (0.41), CI 84-89 (84), SI 81-92 (92), REL 10-16 (13), FLI 22-27 (26), PSI 1.5-2.3 (1.6), MFI 107-119 (107), ACI1 69-73 (70), ACI2 94-105 (94).

Small-sized species; general body color a mottled dark brown to light orange-brown, with mandibles and appendages lighter, usually orange-brown to yellow-brown; setae golden brown; mandible with 6-7 teeth (usually 6), consisting of 2-3 distinct apical teeth, a distinct, usually well-defined basal tooth, and 2-3 inner teeth, which are sometimes worn and indistinct; basal margin of mandible sinuous and always with a small basal notch containing a tooth; mandible mostly smooth and shining, with scattered piligerous punctae and basal striae; anterior clypeal margin viewed at an anterodorsal angle weakly to strongly undulating (appearing nearly flat in full-face view), often forming 4 blunt teeth, median undulation (emargination) sometimes narrow and notch-like; median lobe of clypeus lacking a distinct pair of longitudinal carinulae, either completely smooth, or with faint irregular striations (type population), apex of lobe with a transverse carina, remainder of clypeus mostly smooth and shiny; posterior extension of clypeus between antennal insertions very narrow (PCW 0.01-0.02), with sides subparallel and inner margins of frontal lobes almost touching anteriorly; frontal lobes of moderate width (FLD 0.11-0.14, FLI 22-27), not obscuring torular lobes in full-face view; head appearing subrectangular (CI 84-89), with posterior margin depressed medially; eyes small (EL 0.05-0.09, REL 10-16), subcircular to slightly ob long, with 3-5 ommatidia at greatest diameter; face densely sculptured, usually mostly rugoreticulate, with longitudinal rugae medially, but sometimes reticulae less distinct and interconnected, interstices lightly punctate; scape relatively short, not reashing posterior margin of head when laid back (SI 81-92), usually of average thickness (type population), but some populations with scape distinctly swollen distally; scape cuticle mostly smooth and somewhat shiny, with scattered piligerous punctae; flagellum with somewhat distinct 4-segmented antennal club, apical segment noticeably enlarged; sculpture on mesosoma variable among populations, lateral surface usually weakly to strongly punctate, with variable number of longitudinal rugulae, dorsal surface of promesonotum variably rugulose-punctate, with pronotum ranging from completely smooth to strongly sculptured, most populations intermediate (type population), pronotum sometimes with a distinct longitudinal carina; propodeal declivity smooth and shiny or with a few transverse carinulae; promesonotum in profile low-domed and roughly symmetrical (type population), or less often flattened and more asymmetrical, with anterior face distinctly longer than posterior; propodeal spines tuberculate or forming short, broad triangular spines (PSL 0.07-0.14, PSI 1.5-2.3); metanotal grove usually well demarcated, of moderate depth and width; petiole of moderate length (PL/HW 0.47-0.56), average-looking; node in profile somewhat small (PH/PL 0.57-0.64), subconical, with anterior face slightly longer and more sloping than posterior face, node dorsum in profile rounded, pointing vertical to slightly posteriad; postpetiole in profile subcircular, usually appearing similar in size to petiolar node (type population), but sometimes slightly larger and more bulging (PPH/PH 0.86-1.08); petiole and postpetiole lightly to somewhat strongly punctate, with nodes variably smooth and shiny; gaster mostly smooth and shiny, with scattered piligerous punctae; most of body dorsum with very short suberect to decumbent pilosity; scapes with a dense layer of decumbent to appressed setae; gastral pilosity consisting of a dense decumbent (type population) to appressed layer of setae, and a much sparser layer of suberect setae, which is sometimes difficult to see among decumbent setae; setae on legs mostly appressed, with a few suberect setae on coxae and femoral venters.

Queen description.

(5 measured) HL 0.56-0.67 (0.66), HW 0.50-0.59 (0.59), FLD 0.12-0.15 (0.15), PCW 0.02-0.03 (0.03), SL 0.41-0.51 (0.51), EL 0.13-0.15 (0.15), ACL 0.41-0.51 (0.51), ML 0.77-0.92 (0.91), PrW 0.43-0.52 (0.52), PSL 0.10-0.11 (0.10), SDL 0.06-0.08 (0.07), PL 0.27-0.32 (0.32), PH 0.16-0.19 (0.19), PW 0.14-0.16 (0.16), PPL 0.15-0.19 (0.19), PPH 0.16-0.19 (0.19), PPW 0.17-0.21 (0.21), MFL 0.44-0.55 (0.54), MTL 0.37-0.46 (0.46), CI 84-91 (89), SI 80-90 (86), REL 25-26 (26), FLI 24-27 (25), PSI 1.3-1.8 (1.5), MFI 103-115 (108), ACI1 69-72 (69), ACI2 95-100 (100).

Same as worker except for standard queen modifications and as follows: pronotum transversely rugose to rugoreticulate laterad, becoming punctate mesad; mesoscutum with narrow strip of smooth cuticle extending from anterior margin to about midpoint along midline; mesopleuron mostly smooth and shiny; propodeum mostly with transverse carinulae that wrap around surface, or less often mostly punctate; propodeal spines smaller (PSL 0.10-0.11, PSI 1.3-1.8).

Male.

Unknown.

Biology.

Stenamma saenzae is known almost exclusively from extracts of sifted leaf litter, with only a few queens collected from flight intercept traps in Belize. It is restricted to montane wet forest environments (e.g. cloud forest, mesophyll forest, pine cloud forest, oak-pine forest, liquidambar-oak-pine forest) and has been collected from 1000-2100 m elevation. Dealate queens as well as workers are commonly collected from leaf litter, suggesting that nests might be located within this stratum.

Comments.

Based on overall size and form, Stenamma saenzae might be confused with Stenamma crypticum , Stenamma nanozoi , or Stenamma excisum , but out of these species, Stenamma nanozoi is the only species to share the small tooth on the basal margin of the mandible. Stenamma saenzae can be easily separated from Stenamma nanozoi by comparing gastral pilosity, which in the latter species, is composed mainly of a sparse layer of thickened suberect setae. Tentative molecular phylogenetic results show Stenamma saenzae as sister to a clade that includes Stenamma catracho , Stenamma crypticum , and Stenamma monstrosum (Branstetter unpublished data).

Stenamma saenzae shows considerable morphological variability among populations. From this variation, I describe two variants that differ significantly from the type phenotype (indicated above). Variant 1 (Figure 147 A–C) occurs mainly in central Guatemala (Biotopo Quetzal, Purulhá) and has the following distinguishing features: pronotal dorsum smooth and shiny; postpetiole more bulging, appearing larger than petiolar node; head somewhat enlarged. Although distinct from the type population, I find intermediate phenotypes at intervening localities, causing me to conclude that this variation is probably intraspecific, and likely due to environmental effects on size and sculpture. Supporting this view is the observation that the locality Biotopo Quetzal, where variant 1 is most distinct, is an especially cool, wet cloud forest site.

Variant 2 (Figure 147 D–F) is known from the localities La Unión in eastern Guatemala and Cusuco in northwestern Honduras, and it has the following distinguishing character states: overall body size distinctly smaller; antennal scapes thickened distally; mesosoma and waist strongly punctate, with rugulae reduced; promesonotum in profile flatter, and more asymmetrical; propodeal spines larger and more broadly triangular; lower layer of gastral setae appressed (rather than decumbent), allowing the suberect layer to be clearly visible. Unlike variant 1, I do not find intermediate phenotypes between variant 2 and the other forms, suggesting that this variant is more isolated and perhaps represents a distinct species. Because this variant is not sympatric with the other forms, I choose to include it within Stenamma saenzae until more data become available. Preliminary molecular results show specimens from La Unión and Cusuco to be sister taxa, nested inside the larger Stenamma saenzae clade.

Material examined.

BELIZE:Cayo: Chiquibul N.P., Doyle’s Delight, 16.49194°N, 89.04444°W, 1000m, 25-28 Aug 2007 (P. W. Kovarik); Chiquibul N.P., Doyle’s Delight, 16.49305°N, 89.04694°W, 1100m, 19-28 Aug 2007 (P. W. Kovarik); GUATEMALA: Baja Verapaz: Biotopo Quetzal, 15.21307°N, 90.21512°W, 1750m, 7 May 2009 (LLAMA), Biotopo Quetzal, 15.2142°N, 90.2163°W, 1680m, 8 Jul 2007 (M. G. Branstetter); Purulhá, Biotopin, 15.21535°N, 90.21618°W, 1698m, 26-30 Mar 2008 ( Méndez et al.); 7.3km E Purulhá, [ca. 15.2667°N, 90.132°W], 1700m, 19 May 1991 (R. S. Anderson); 8km S Purulhá, [ca. 15.1944°N, 90.2000°W], 1660m, 20 May 1991 (R. S. Anderson); Ranchito El Quetzal, 15.21508°N, 90.22003°W, 1700m, 20 Sep 2008 (R. S. Anderson); Ranchito El Quetzal, 15.21308°N, 90.22245°W, 1870m, 20 Sep 2008 (R. S. Anderson); Salamá, Hotel Posada del Quetzal 1, 15.19710°N, 90.21169°W, 1600m, 26-30 Mar 2008 ( Méndez et al.); Suchitepéquez: 4km S. Vol. Atitlán, 14.55112°N, 91.19848°W, 1750m, 15 Jun 2009 (LLAMA); Zacapa: 2km SE La Unión, 14.95396°N, 89.27645°W, 1430m, 12 May 2009 (LLAMA); 2km SE La Unión, 14.94654°N, 89.27600°W, 1550m, 12 May 2009 (LLAMA); HONDURAS: Cortés: PN Cusuco, 15.48839°N, 88.23592°W, 1260m, 31 May 2010 (LLAMA); PN Cusuco, 15.48940°N, 88.23746°W, 1290m, 20 May 2010 (LLAMA); PN Cusuco, 15.48965°N, 88.23383°W, 1300m, 31 May 2010 (LLAMA); MÉXICO:Chiapas: Cerro de Tapalapa, 17.18786°N, 93.12308°W, 2260m, 27 May 2008 (R. S. Anderson); 4.5km NE Coapilla, 17.1653°N, 93.1389°W, 1800m, 12 Jul 2007 (R. S. Anderson); 5km NE Coapilla, 17.17598°N, 93.13269°W, 1990m, 25 May 2008 (LLAMA); 5km NNW Coapilla, 17.18273°N, 93.15184°W, 1915m, 25 May 2008 (LLAMA); 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); L. Pojoj, Lagos de Montebello, 16.10°N, 91.67°W, 1500m, 21 Dec 1991 (P. S. Ward); Lagos de Montebello, Cinco Lagos, 16.1012°N, 91.6740°W, 1600m, 21 Jul 2007 (R. S. Anderson); Lagunas de Mon tebello, Cinco Lagos, [ca. 16.1167°N, 91.6833°W], 2200m, 21 Sep 1991 (R. S. Anderson); 6km SW Ocosingo, [ca. 16.8672°N, 92.0787°W], 1400m, 22 Sep 1991 (R. S. Anderson); 2.1km NW Puebla Nuevo Solistahuacan, Yerbabuena Preserve, [ca. 17.183°N, 92.900°W], 2070m, 23 Sep 1992 (R. S. Anderson); 13km N Pueblo Nuevo Solistahuacán, [ca. 17.211°N, 92.964°W], 1860m, 26-27 Aug 1973 (A. F. Newton); 5km E Rayón, 17.217°N, 92.967°W, 1700m, 23 Dec 1991 (P. S. Ward); 8.9km E Rayon, 17.200000°N, 92.91633°W, 1500m, 19 Sep 1991 (R. S. Anderson); 16km WSW S. Cristóbal, 16.69496°N, 92.77234°W, 1763m, 7 Jul 2008 (R. S. Anderson).