Pogonomyrmex granulatus, Johnson, 2021

Johnson, Robert A., 2021, A taxonomic revision of South American species of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae). Part II, Zootaxa 5033 (1), pp. 1-230 : 85-89

Pogonomyrmex granulatus NEW SPECIES

( Figures 38–39 )

Distribution—36C

Holotype worker [ MACN: CASENT0235302 ]: 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) . Paratypes, same data as holotype: IFML (3 workers) , MACN (9 workers) , MCZC (4 workers, 2 males) , LACM (3 workers) , RAJC (8 workers, 1 male) , USNM (3 workers) . Additional paratype series from the same locality and date—RAJ#4339: IFML (3 workers) , MACN (4 workers, 2 males) , RAJC (3 workers, 6 males) ; RAJ#4341: MACN (9 workers) , RAJC (9 workers) , UCDC (3 workers); RAJ#4342: IFML (3 workers) , MACN (3 workers) , RAJC (3 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) striae cover anterior one-half or more of first gastral tergum, (2) head and mesosoma blackish to black, gaster dark ferruginous orange to orangish-black, (3) relatively small (HW = 1.42–1.70 mm; PNW = 0.96–1.14 mm; ML = 1.67–2.12 mm), (4) mandibles with six teeth, (5) superior propodeal spines consist of tubercles, denticles, or short blunt teeth, (6) in profile, most hairs on cephalic dorsum moderately long, length of numerous hairs> 0.4× MOD, (7) in profile, rugae posterior to eyes coarse, irregular, sometimes circumocular or converging anterior to posterior corners, and (8) interrugae on cephalic dorsum strongly granulate, weakly dull to dull, with a beaded appearance ( Figure 38 ).

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. Longitudinal rugae on cephalic dorsum prominent, weakly wavy to irregular; in full-face view, medial rugae diverging toward posterior corners of head. In profile, rugae posterior to eyes coarse, irregular, sometimes circumocular or converging anterior to posterior corners, interrugae strongly granulate, weakly dull to dull, with a beaded appearance. Interrugae on cephalic dorsum strongly granulate, dull, with a beaded appearance. Posterior corners rugose; interrugae weakly to strongly granulate, weakly dull to weakly shining. Anterior margin of clypeus concave; dorsal surface with numerous subparallel, longitudinal rugae. Numerous long, curved, bristle-like, cream colored to light yellowish ammochaetae project from anterior margin of clypeus and basolateral margin of mandibles. Mandibles with six teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.19–0.23× HL. In profile, eyes situated near middle of head, OMD = 1.08–1.44× MOD. Antennal scapes relatively long (SI = 67.05–78.18), reaching posterior corners to surpassing posterior corners 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 profile and dorsal views, humeral shoulders of pronotum 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 shoulders of pronotum; rugae on humeral shoulders of pronotum and pronotal sides often weakly rugoreticulate to vermiculate. Mesopleura with wavy to irregular rugae angling posterodorsally. Dorsum of propodeum weakly rugoreticulate or with transverse to irregular rugae that traverse anteroventrally on sides. Superior propodeal spines consist of tubercles, denticles, or short blunt teeth. Inferior propodeal spines forming a broadly rounded to subangulate process, height similar to or greater than length of superior spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to strongly granulate, dull to weakly shining. Legs weakly to strongly coriarious, dull to weakly shining.

Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin with a broadly rounded tooth-like process. In profile, petiolar node broadly rounded with anterior surface shorter than posterior surface; apex weakly angulate. In dorsal view, petiolar node longer than wide, widest near spatulate anterior margin; posterior surface 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 finer, denser than those on posterior surface of petiolar node; rugae near anterior margin of posterior surface of petiolar node and dorsum of postpetiole sometimes oblique; interrugae on both surfaces moderately granulate, weakly shining. First gastral tergum with striae over anterior one-half or more of segment, posterior margin with striae or strongly coriarious, dull.

Erect, whitish pilosity moderately abundant on head, variable in length, longest hairs not exceeding MOD; in profile, length of numerous hairs on cephalic dorsum> 0.4× 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, petiolar node, postpetiole, gastral terga with erect, moderately dense setae, mostly similar in length, only those on posterior gastral terga sometimes approaching MOD. Bicolored: head and mesosoma black; gaster dark ferruginous orange to orangish-black, a black transverse band often present along posterior margin of terga ( Figure 38 ).

Queen. Unknown.

Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) striae extend over anterior one-half or more of first gastral tergum, (2) subparallel-parallel, longitudinal rugae extend over most of anepisternum and katepisternum, (3) notauli present, weakly to moderately impressed, often only visible along anterior margin of mesoscutum, (4) in profile, irregular rugae immediately posterior to eyes surrounded by rugae that form circumocular whorls, and (5) bicolored: head and mesosoma black, gaster dark ferruginous orange ( Figure 39 ).

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.

Additional material examined. ARGENTINA: Salta: Valle Encantado , 1960 m, Dec 17, 2001 ( RAJC; UCDC) ( Figure 36C ) .

Etymology. The specific epithet, granulatus (from Latin, granulatus = granular), is an adjective that refers to the strongly granulate interrugae on the cephalic dorsum.

Discussion. Pogonomyrmex granulatus might co-occur with one or more P. rastratus -group species, but its coloration (black head and mesosoma and light to dark ferruginous orange gaster) and striae that cover the anterior one-half or more of the first gastral tergum distinguish it from all congeners except P. catanlilensis , P. forelii , and P. varicolor . Pogonomyrmex granulatus is distinguished from P. forelii by superior propodeal spines that consist of tubercles, denticles, or short teeth with their length less than 0.5× the distance between their bases. In P. forelii , the superior propodeal spines are moderately long to long with a length> 0.6× the distance between their bases. Pogonomyrmex granulatus is separated from P. catanlilensis by: (1) superior propodeal spines consist of tubercles, denticles, or short blunt teeth, but never moderately long to long spines, (2) relatively small (HW = 1.42–1.70 mm; PNW = 0.96–1.14 mm; ML = 1.67–2.12 mm), (3) in profile, most hairs on cephalic dorsum moderately long, length of numerous hairs> 0.4× MOD, and (4) mandibles with six teeth. In P. catanlilensis : (1) superior propodeal spines consist of tubercles, denticles, or short teeth to long spines, (2) relatively large (HW = 1.67–2.04 mm; PNW = 1.15–1.42 mm; ML = 2.01–2.76 mm), (3) in profile, most hairs on cephalic dorsum short, length of most hairs <0.2× MOD, and (4) mandibles with six to eight teeth (> 50% with seven to eight teeth). Pogonomyrmex granulatus is separated from P. varicolor by: (1) superior propodeal spines consist of tubercles, denticles, or short blunt teeth, (2) in profile, rugae posterior to eyes coarse, irregular, sometimes circumocular or converging anterior to posterior corners, and (3) interrugae on cephalic dorsum strongly granulate, weakly dull to dull, with a beaded appearance. In P. varicolor : (1) the superior propodeal spines consist of short to long spines for at least some workers in a series, (2) in profile, rugae posterior to eyes fine, dense, regular, converging at or near posterior corners, and (3) interrugae on cephalic dorsum smooth and shining to moderately coriarious, weakly shining, rarely with a beaded appearance.

Biology. Pogonomyrmex granulatus workers are solitary foragers. Nests vary from an entrance lacking a tumulus to one that is approximately 10 cm in diameter. The easiest method to find nests is bait workers with cookie crumbs, then follow them back to the nest. Partial nest excavations indicated that colonies are relatively small and probably contain up to approximately 500 workers (R.A. Johnson, pers. obs.). Males were collected on 20 January, suggesting that mating flights occur during the austral summer.

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 second collection locale was on a steep rocky slope with grasses and Ephedra sp. (Ephedraceae) . Pogonomyrmex granulatus inhabits elevations from 1960–3300 m. This species is only known from the Central Andean puna ecoregion, as defined by Olson et al. (2001) ( Figure 36C ).

Figures

FIGURE 36. Geographic distribution of: (A) Pogonomyrmex excelsior, (B) P. forelii, and (C) P. granulatus. The large black circle in each panel denotes the type locality.

FIGURE 38. Photographs of Pogonomyrmex granulatus holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0235302). Photographs by Will Ericson from www.AntWeb.org.

FIGURE 39. Photographs of Pogonomyrmex granulatus paratype male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0235301). Photographs by Shannon Hartman & Will Ericson from www.AntWeb.org.