Pogonomyrmex atacama, 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 : 45-50

Pogonomyrmex atacama NEW SPECIES

( Figures 2C–D , 18–20 )

Distribution—14C

Holotype worker [ MNNC: CASENT0922565 ]: CHILE, Antofagasta: El Loa Province: Rt 23 at 35.9 km NE Socaire, 23 o 50.0’S 67 o 51.9’W, 12,720’ (3855 m), 23 March 2017 ( RA Johnson #5837) . Paratypes, same data as holotype: IFML (3 workers) , LACM (6 workers) , MACN (3 workers) , MCZC (6 workers) , MNNC (12 workers) ; RAJC (54 workers, 4 alate queens), UCDC (3 workers) , USNM (6 workers) . Additional paratype series from same locality and date–RAJ #5838; RAJC (9 workers) ; RAJ #5839; IFML (3 workers) , LACM (3 workers) , MACN (3 workers) , MCZC (3 workers) , MNNC (6 workers) ; RAJC (9 workers) , USNM (3 workers) ; RAJ #5840; MNNC (5 workers) ; RAJC (18 workers) , UCDC (3 workers), USNM (3 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) first gastral tergum with striae along base to extending over anterior one-third to one-half of medial portion of segment, rest of tergum smooth and shining to strongly shining, (2) longitudinal rugae on dorsum of mesonotum regular, anterior margin of pronotum usually with one to few transverse rugae, (3) mesosoma ferruginous orange, reddish-orange, or orangish brown, (4) superior propodeal spines consist of short to moderately long spines with length greater than width at base, (5) height of inferior propodeal spines less than length of superior propodeal spines, (6) posterior corners of head usually smooth and shining to strongly shining, (7) mandibles with seven teeth, (8) rugae on medial portion of clypeus converge anterad to form up to several concentric, narrowly rounded Vs, and (9) rugae on dorsum of postpetiole mostly longitudinal ( Figure 18 ).

Measurements — holotype (n = 12 paratypes). HL 1.68 (1.39–1.70); HW 1.73 (1.47–1.79); MOD 0.42 (0.36– 0.42); OMD 0.38 (0.32–0.48); SL 1.31(1.06–1.34); PNW 1.09 (0.98–1.15); HFL 1.69 (1.41–1.78); ML 1.92 (1.65– 2.04); PW 0.42 (0.37–0.45); PPW 0.58 (0.50–0.65). Indices: SI 75.72 (67.95–79.01); CI 102.98 (101.96–113.82); OI 24.28 (22.22–26.53); HFI 97.69 (94.15–101.75).

Description. Head quadrate to wider than long (CI = 101.96–113.82); posterior margin flat to weakly convex in full-face view. Longitudinal rugae on cephalic dorsum prominent; in full-face view, medial rugae not diverging to diverging toward posterior corners; for most workers, posterior margin with transverse rugae medially to along entire margin. Rugae on medial portion of clypeus converge anterad to form up to several concentric, narrowly rounded Vs. Interrugae on cephalic dorsum moderately to strongly granulate-punctate, with a beaded appearance, weakly shining; posterior corners smooth and shining to strongly shining, faint striae visible on occasional workers. Anterior margin of clypeus moderately concave, dorsum with numerous subparallel, longitudinal rugae. Numerous long, curved, bristle-like, yellowish macrochaetae project from anterior margin of clypeus and basolateral margin of mandibles. Mandibles with seven teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.23–0.29× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 0.90–1.24× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head.Antennal scapes (SI = 67.95–79.01) failing to reach posterior corners by less than length of basal funicular segment. Antennal scapes smooth and shining; basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile weakly convex; all mesosomal surfaces with prominent, wavy to irregular rugae. In dorsal view, humeral shoulders of pronotum enlarged, dorsolateral margin weakly to moderately angulate. Promesonotal suture usually weakly to moderately impressed. Wavy to irregular, longitudinal rugae on mesonotum continue onto pronotum, lateral rugae diverging to humeral shoulders of pronotum with one to several transverse rugae along anterior margin of pronotum. Irregular rugae on pronotal sides traverse ventrally or posteroventrally. Irregular rugae on mesopleura angle posterodorsally; irregular transverse, oblique, or nearly longitudinal rugae on dorsum of propodeum traverse ventrally or anteroventrally on sides. Superior propodeal spines consist of short, triangular teeth to long spines, lacking well defined keel that connects spines. Inferior propodeal spines moderately well developed, wider than high, apex weakly rounded, height usually less than length of superior spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to moderately granulate-punctate, weakly shining to smooth and shining. Legs weakly coriarious, weakly shining to shining.

Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin with well developed rounded process. In profile, posterior surface of petiolar node weakly convex; node asymmetrical with anterior surface longer than posterior surface, apex subangulate to weakly rounded. In dorsal view, petiolar node longer than wide, sides subparallel, narrowest posterad, anterior margin spatulate to broadly rounded. Posterior surface of petiolar node with regular to wavy transverse to occasionally oblique rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, maximum width and length about equal. Rugae on dorsum of postpetiole mostly longitudinal, finer, denser than those on posterior surface of petiolar node, interrugae on both surfaces weakly granulate, weakly shining to shining. Striae extend over anterior one-third to one-half of medial portion of first gastral tergum, posterior portion smooth and shining to strongly shining.

Erect, mostly short to medium length, whitish pilosity moderately abundant on head. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent whitish to pale yellow setae. Rest of body with moderately dense, erect, mediumlength, whitish to pale yellow setae. Head and mesosoma dark ferruginous orange to orangish-brown, mesosoma sometimes slightly darker than head; mandibles, antennae, legs, petiolar node, postpetiole, gaster dark brownishorange ( Figure 18 ).

Queen diagnosis. Queens of this species are diagnosed by the following combination of features: (1) striae cover anterior one-quarter or more of first gastral tergum, (2) medioposterior one-quarter to one-third or more of first gastral tergum (including posterolateral margins) smooth and shining, (3) mesopleura and propodeum ferruginous orange to orangish-black, (4) posterior corners smooth and shining, faint rugae sometimes present, (5) in dorsal view, interrugae on mesoscutum weakly coriarious, shining, and (6) transverse rugae cover posterior surface of petiolar node and dorsum of postpetiole ( Figures 2C–D , 19 ).

Measurements —(n = 4 paratypes). HL 1.54–1.64; HW 1.68–1.74; MOD 0.38–0.42; OMD 0.39–0.41; SL 1.24–1.28; PNW 1.22–1.26; HF 1.58–1.72; ML 2.05–2.22; PW 0.40–0.49; PPW 0.62-0.63. Indices: SI 71.26–75.60; CI 103.05–111.04; OI 22.62–24.14; HFI 94.05–101.78.

Description. With caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head. In full-face view, head quadrate to slightly wider than long (CI = 103.05–111.04), widest just posterior to eyes, posterior margin flat to weakly convex. Longitudinal rugae on cephalic dorsum prominent, wavy; in full-face view, medial rugae weakly diverging to diverging toward posterior corners of head; interrugae on cephalic dorsum weakly to moderately granulate-punctate, with a weakly beaded appearance, weakly shining; posterior corners smooth and shining or with faint rugae. Mandibles with six to seven teeth, often with one to two additional denticles between teeth, dorsal surface coarsely rugose. Psammophore well developed.

All mesosomal surfaces with subparallel, regular to wavy rugae; interrugae on mesoscutum weakly granulate, weakly shining, interrugae on other parts of mesosoma weakly to moderately granulate, weakly shining; superior propodeal spines consist of triangular teeth, width at base similar to length; inferior propodeal spines wider than tall, apex weakly rounded to rounded, height less than to similar to length of superior propodeal spines. Peduncle of petiole long, anteroventral margin with a weakly to moderately developed, broadly rounded process that narrows, then continues posterad parallel to dorsal surface. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex angulate. Posterior surface of petiolar node with wavy to irregular, transverse to arcuate rugae, weakly shining. In dorsal view, postpetiole wider than long; dorsum with wavy to irregular, transverse to strongly arcuate rugae that are finer, denser than those on posterior surface of petiolar node, interrugae on both surfaces weakly granulate-punctate, weakly shining. Striae cover anterior one-third to one-half of first gastral tergum, rest of segment smooth and shining to strongly shining. Most body surfaces with moderately abundant suberect to erect, short to medium-length, whitish setae. Head ferruginous orange; mesosoma dark orange to orangish-black or blackish-orange; gaster blackish or with first gastral tergum orangish-black; petiole, postpetiole, legs, antennae, black ( Figures 2C–D , 19 ).

The queen of P. atacama appears to be brachypterous. The body retains all structures of a fully alate queen, and the wings retain all cells of a fully alate queen. However, the wings are reduced in size as they do not extend to the posterior margin of the gaster, and the tips are weakly to strongly concave rather than weakly to moderately convex as in fully alate queens. Additionally, in profile the anterior margin of the mesoscutum rises at an approximately 45 o angle to meet the dorsal surface ( Figure 2D ) rather than having a vertical anterior face as occurs in fully alate queens ( Figures 2F &2H ).

Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) striae extend over anterior one-third to one-half of first gastral tergum, (2) in profile, rugae forming circumocular whorls posterior to eyes, (3) notauli present, and (4) head and mesoscutellum mostly dark ferruginous orange ( Figure 20 ).

Measurements —(n = 1). HL 1.22; HW 1.24; MOD 0.48; OMD 0.14; SL 0.38; HFL 1.50; ML 2.12; PW 0.47; PPW 0.62. Indices: SI 30.65; CI 101.64; OI 38.71; HFI 120.97.

Additional material examined. CHILE: Antofagasta: Rt 23 at 12.5 km NE Socaire, 12,560’, Mar 23, 2017 ( RAJC); Rt 23 at 56.2 km NE Socaire, 13,520’, Mar 23, 2017 ( RAJC) ( Figure 14C ) .

Etymology. The specific epithet, atacama , is a noun in apposition and invariant in form that is derived from a group of Native Americans that lived in northeastern Chile.

Discussion. Pogonomyrmex atacama likely co-occurs with P. loaensis and possibly other P. rastratus -group species. Pogonomyrmex atacama and P. loaensis are similar, but they can be distinguished based on the following characters. In P. atacama : (1) striae extend over the anterior one-third to one-half of the medial portion of the first gastral tergum, and (2) posterior corners of head usually smooth and shining to strongly shining. In P. loaensis : (1) striae extend over the anterior two-thirds or more of the medial portion of the first gastral tergum, and (2) the posterior corners of the head rugose. Pogonomyrmex atacama is distinguished from most other P. rastratus group species based on striae extending over the anterior one-third to one-half of the first gastral tergum. Pogonomyrmex bolivianus is the only species with this character that is likely to be confused with P. atacama . In P. atacama : (1) the posterior corners of head smooth and shining to strongly shining for most to all workers in a series, (2) mandibles with seven teeth, (3) longitudinal rugae on dorsum of mesonotum regular; anterior margin of pronotum usually with one to few transverse rugae, (4) superior propodeal spines consist of short, triangular teeth to long spines, (5) rugae on dorsum of postpetiole mostly longitudinal, and (6) one to few rugae on medial portion of clypeus converging anterad forming a narrowly rounded V-shaped pattern. In P. bolivianus : (1) the posterior corners of head rugose, (2) longitudinal rugae on dorsum of promesonotum irregular, continuing to anterior margin of pronotum, (3) mandibles with six teeth, (4) superior propodeal spines consist of short, triangular teeth, (5) rugae on dorsum of postpetiole mostly transverse, and (6) rugae on frontal triangle subparallel-parallel, continuing onto clypeus.

Biology. Pogonomyrmex atacama workers are solitary foragers. Nests are placed in open, exposed sites with a tumulus that ranges from 15–20 cm in diameter. Sexuals have been collected on 23 March, indicating that mating flights occur during the austral summer. Partial nest excavations indicated that colonies probably contain up to 1000 workers.

Pogonomyrmex atacama inhabits sites at elevations from 3805–4095 m. This species occurs in the Central Andean dry puna ecoregion, as defined by Olson et al. (2001) ( Figure 14C ).

Figures

FIGURE 2. Closeup photographs of the mesosoma in dorsal view and in profile that distinguish between brachypterous and fully alate queens of Pogonomyrmex: (A–B) dealate brachypterous queen of P. tinogasta (CASENT0235287), (C–D) brachypterous queen of P. atacama (CASENT0922568), (E–F) dealate queen of fully winged P. mapuche (CASENT0280985), and (G–H) fully winged queen of P. spinolae (CASENT0869792). Red arrows (A, B, E, F) show remaining wing scars after the wings have been lost in a brachypterous (A–B) and fully alate queens (E–F). Blue, green, and yellow arrows show morphological differences between brachypterous and fully alate queens. Blue arrows show the much enlarged pronotum in brachypterous queens (A & C) compared to the pronotum of fully alate queens (E & G). Green arrows show differences in the profile of the pronotum, with brachypterous queens having either a sloping (B) or vertical pronotum (D), whereas fully alate queens always have a vertical pronotum (F & H). Yellow arrows show brachypterous queens with the mesoscutum meeting the pronotum on a horizontal plane (A) or the mesoscutum slopes at 45o from the juncture of the pronotum to the dorsum of the mesoscutum (D), whereas the mesoscutum continues vertically from the pronotum in fully alate queens (F & H). Photographs by Michele Esposito and Robert Johnson from www.AntWeb.org.

FIGURE 14. Geographic distribution of: (A) Pogonomyrmex apterogenos, (B) P. araucania, and (C) P. atacama. The large black circle in each panel denotes the type locality.

FIGURE 18. Photographs of Pogonomyrmex atacama holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922565). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 19. Photographs of Pogonomyrmex atacama paratype alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922568). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 20. Photographs of Pogonomyrmex atacama male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0923353). Photographs by Michele Esposito from www.AntWeb.org.