Pogonomyrmex granulatus Johnson NEW SPECIES

Holotype worker: ARGENTINA, Salta: Departamento Cachi, Valle Encantado, 20.2 km NE Jct Rts 33 & 2, 25º11.3’S, 65º51.2’W, 10,880 feet (3300 m), 20 January 2010 (R.A. Johnson #4340) [MACN]. Paratypes, same data as holotype: FML (3w), MACN (9w), MCZ (4w, 2m), LACM (3w), RAJC (8w, 1m), USNM (3w). Additional paratype series from the same locality and date - RAJ#4339: FML (3w), MACN (4w, 2m), RAJC (3w, 6m); RAJ#4341: MACN (9w), RAJC (9w), UCDC (3w); RAJ#4342: FML (3w), MACN (3w), RAJC (3w).

Worker

Diagnosis. The combination of: (1) longitudinal striae on first gastral tergum, (2) strongly granulate interrugal spaces on head, (3) superior propodeal spines consisting of blunt tubercles or denticles, and (4) bicolored, entire body black except for dark ferruginous to orangish-black gaster, black transverse bands often along posterior margins of terga uniquely characterize this species.

Measurements - holotype (n = 12 paratypes). HL 1.57 (1.36-1.70); HW 1.57 (1.42-1.70); MOD 0.32 (0.28-0.36); OMD 0.42 (0.38-0.49); SL 1.19 (1.11-1.29); PNW 1.08 (0.96-1.14); HFL 1.44 (1.39-1.72); ML 1.88 (1.67-2.12); PW 0.41 (0.36-0.46); PPW 0.55 (0.51-0.63). Indices: SI 75.80 (67.05-78.18); CI 100.00 (101.23-110.81); OI 20.38 (18.75-22.36); HFI 91.72 (94.97-104.88).

Description. Head quadrate to wider than long (CI = 100.00-110.81), widest just posterior to eye; posterior margin flat in full-face view. Longitudinal cephalic rugae prominent, slightly wavy to irregular, in full-face view median rugae diverging toward posterior corners of head. In side view, rugae posterior to eyes converging at or near vertex; vertex rugose. Cephalic interrugal spaces strongly granulate, dull. Anterior margin of clypeus concave; dorsal surface with numerous subparallel longitudinal rugae. Mandible with six teeth; mandibular dorsum coarsely rugose. Numerous long, curved, bristle-like, cream colored to light yellowish hairs project from anterior margin of clypeus and basolateral margin of mandibles. MOD ranging from 0.19-0.23x HL. Eyes in profile situated near middle of head, OMD = 1.08-1.44x MOD. Antennal scapes relatively long (SI = 67.05-78.18), reaching vertex or surpassing it by less than length of basal funicular segment; entire scape with longitudinal striae, dull to weakly shining. Basal flange of scape flattened and well developed with carinate margin. Psammophore well developed.

Mesosomal profile strongly convex; all mesosomal surfaces with prominent wavy to irregular rugae. In side and dorsal views, humeral shoulders sometimes angulate, weakly elevated above flattened medial portion of pronotum. Promesonotal suture weakly impressed on occasional workers. Dorsum of promesonotum with irregular longitudinal rugae, lateral rugae often angling toward humeral angles; rugae on humeral angles and sides of pronotum often weakly rugoreticulate to vermiculate; rugae on pronotal sides continue ventrally or posteroventrally. Mesopleura with wavy to irregular rugae angling posterodorsally. Dorsum of propodeum with transverse to irregular rugae, occasionally slightly rugoreticulate, that traverse anteroventrally on sides. Propodeum armed with short blunt tubercles or denticles that are much shorter than the distance between bases. Inferior propodeal spines moderately well developed forming a broadly rounded to subangulate process, height similar to or greater than length of superior tubercles. Propodeal spiracles narrowly ovate. Interrugal spaces on mesosoma weakly to strongly granulate, dull to weakly shining. Legs weakly to strongly coriarious, dull to weakly shining.

Petiolar peduncle about 0.6x as long as petiole, anteroventral margin with broadly rounded tooth-like process. In side view, petiolar node broadly but asymmetrically rounded with anterior surface shorter than posterior surface. Apex of node weakly angulate. In dorsal view, petiolar node longer than wide, widest anteriorly with spatulate anterior margin; posterior face and sides with wavy to irregular, transverse rugae that traverse ventrally on sides. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin; maximal width about equal to length; dorsum and sides with transverse to wavy rugae that are weaker, more closely spaced than those on petiole; rugae near anterior margin of posterior face of petiole and dorsum of postpetiole sometimes oblique. Interrugal spaces of petiole and postpetiole moderately granulate, weakly shining. Dorsum of first gastral tergum with numerous fine longitudinal striae, silky in appearance.

Erect whitish pilosity moderately abundant on head, variable in length, longest hairs not exceeding MOD. Moderately abundant suberect to semidecumbent pilosity on scape, abundant decumbent hairs on funicular segments. Legs with moderately abundant semidecumbent to suberect white setae. Mesosoma, petiole, postpetiole, gastral terga with moderately dense, erect setae, mostly similar in length, only those on posterior gastral tega sometimes approaching MOD. Bicolored, entire body black except for dark ferruginous orange to orangish-black gaster, black transverse bands often along posterior margins of terga.

Queen. Unknown.

Male

Diagnosis.

Measurements – (n = 11 paratypes). HL 1.11-1.32; HW 1.15-1.29; MOD 0.40-0.47; OMD 0.19-0.29; SL 0.39-0.49; HFL 1.49-1.70; ML 1.94-2.23; PW 0.40-0.52; PPW 0.61-0.68. Indices: SI 32.50-38.02; CI 96.21-109.01; OI 33.33-37.01; HFI 121.6-133.86.

Description.

Additional material examined. ARGENTINA: Salta: Valle Encantado, 1960 m, Dec. 17, 2001 (RAJC).

Etymology. The specific epithet, granulatus (from Latin, granulatus = granular), is an adjective that refers to the strongly granulate interrugal spaces on the head.

Discussion. Pogonomyrmex granulatus is not known to co-occur with any congeners, but P. weiseri occurs 17 km west of the type locality. Pogonomyrmex granulatus can be distinguished from P. weiseri based on the following characters: (1) superior propodeal spines reduced to denticle or tubercle, (2) longitudinal rugae on dorsum of mesosoma irregular, interrugal spaces granulate, dull to weakly shining, and (3) head and mesosoma black, gaster ferruginous orange to orangish-black. In P. weiseri: (1) the superior propodeal spines are well developed with an acuminate tip, (2) longitudinal rugae on dorsum of mesosoma are regular to slightly irregular, interrugal spaces smooth and shining to weakly coriarious, weakly shining, and (3) the head and gaster are orangish, and the mesosoma is orangish-black to black.

Pogonomyrmex granulatus might also be confused with P. pronotalis, P. catanlilensis, and P. mendozanus because all four species have a similar coloration. Pogonomyrmex granulatus can be distinguished from P. pronotalis and P. mendozanus based on the following charcters: (1) first gastral tergum mostly covered with fine striae, dull to weakly shining, and (2) the superior propodeal spine reduced to a denticle or tubercle. In P. pronotalis and P. mendozanus, the first gastral tergum is smooth and shining (lacking fine striae), and superior propodeal spines are moderately to well developed and acuminate. Pogonomyrmex granulatus can be distinguished from P. catanlilensis based on the following characters: (1) superior propodeal spines reduced to a denticle or tubercle, and (2) in lateral view, the node of petiole is rounded to subangulate. In P. catanlilensis, the superior propodeal spines are moderately to well developed and acuminate, and the petiolar node is angulate.

BIOLOGY

Nests of all four type series of P. granulatus were in alpine habitat on a hillside with vegetation that consisted of grasses, herbaceous perennials, and composites; the substrate consisted of silty, loamy soil with gravel and small rocks. The other site was on a steep rocky slope with grasses and Ephedra sp.; elevations at the two sites ranged from 1960–3300 m (Figure X). Nests were often difficult to locate because the nest entrance varied from an entrance lacking a tumulus to a tumulus that was approximately 10 cm in diameter. Consequently, the easiest method to find nests was to locate and bait foragers, then follow them back to the nest. Workers foraged solitarily during the day. Colonies are relatively small and appeared to consist of approximately 500 workers (R.A. Johnson, pers. obs.). The timing of mating flights is unknown, but males were collected on 20 January, suggesting that flights occur during summer.