Pogonomyrmex mapuche, 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 : 119-123

Pogonomyrmex mapuche NEW SPECIES

( Figures 2E–F , 56–57 )

Distribution—51C

Holotype worker [ MACN: CASENT0280988 ]: ARGENTINA, Neuquén: Departamento Collón Curá , 6.3 km E Jct Rts 237 & 40, 40º25.1’S 70º36.0’W, 2800’ (850 m), 24 January 2011 (R.A. Johnson #4638) . Paratypes, same data as holotype: IFML (3 workers), LACM (6 workers), MACN (6 workers), MCZC (4 workers), RAJC (4 workers), UCDC (3 workers), USNM (4 workers). Additional paratype series from the same locality and date–RAJ #4637: IFML (3 workers), MACN (3 workers), MCZC (3 workers), RAJC (3 workers), USNM (3 workers), RAJ #4639: IFML (2 dealate queens), MACN (3 dealate queens), RAJC (11 dealate queens) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) striae extend over anterior one-half or more of first gastral tergum, posterior margin with striae or moderately to strongly coriarious; posterolateral margins moderately to strongly coriarious, weakly shining to dull, (2) head dark red to reddish-black, promesonotum and first gastral tergum reddish-blackish to black, more posterior terga brown, rest of body blackish to black, (3) superior propodeal spines consist of tubercles or denticles, rarely short acuminate teeth to moderately long spines, (4) inferior propodeal spines wider than high, height usually greater than length of superior propodeal spines, and (5) mandibles with seven teeth for some to most workers in a series ( Figure 56 ).

Measurements — holotype (n = 12 paratypes). HL 1.83 (1.70–1.96); HW 1.97 (1.84–2.07); MOD 0.43 (0.37– 0.43); OMD 0.43 (0.40–0.50); SL 1.44 (1.31–1.56); PNW 1.30 (1.15–1.39); HFL 2.05 (1.79–.07); ML 2.27 (1.98– 2.34); PW 0.51 (0.44–0.59); PPW 0.68 (0.59–0.74). Indices: SI 73.10 (67.35–81.25); CI 107.65 (101.59–114.62); OI 21.83 (19.17–21.54); HFI 104.06 (87.44–103.65).

Description. Head quadrate to wider than long (CI = 101.59–114.62); posterior margin flat in full-face view. Longitudinal rugae on cephalic dorsum prominent; in full-face view, medial rugae continuing to posterior margin or diverging toward posterior corners of head. Interrugae on cephalic dorsum moderately to strongly granulatepunctate, dull to weakly shining, with a beaded appearance; posterior corners rugose, interrugae weakly to strongly granulate-punctate, weakly dull to smooth and shining. Anterior margin of clypeus moderately concave, dorsum with numerous subparallel-parallel, longitudinal rugae. Numerous long, curved, bristle-like, cream colored to light yellowish macrochaetae project from anterior margin of clypeus and basolateral margin of mandibles. Mandibles with six (9 of 34, 26.5%) to seven (21 of 34, 61.8%) teeth or with six on one mandible, seven on the other (3 of 34, 8.8%), rarely eight teeth (1 of 34, 2.9%); mandibular dorsum coarsely rugose. MOD ranging from 0.20–0.24× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 1.00–1.26× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 67.35–81.25) failing to reach posterior corners of head by length of basal funicular segment; scapes with longitudinal striae, interstriae weakly shining to shining; basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile weakly to moderately convex; all mesosomal surfaces with prominent regular to moderately irregular, subparallel-parallel rugae to rugoreticulate. In dorsal view, humeral shoulders of pronotum enlarged, dorsolateral margins weakly to strongly angulate. Promesonotal suture present on occasional workers. Dorsum of mesonotum with weakly regular to strongly irregular, longitudinal rugae that diverge anterad toward humeral shoulders of pronotum or become rugoreticulate on pronotum, medial rugae on mesonotum sometimes converge at promesonotal suture. Pronotal sides rugoreticulate or with irregular rugae that traverse posteroventrally; rugae on mesopleura angle posterodorsally. Superior propodeal spines consist of tubercles to denticles, rarely short, acuminate teeth to moderately long spines; wavy to irregular transverse rugae on propodeal dorsum traverse ventrally or anteroventrally on sides. Inferior propodeal spines wider than high, apex weakly rounded to acuminate, height usually greater than length of superior spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma moderately to strongly granulate-punctate, dull to weakly shining. Legs weakly to moderately coriarious, weakly shining to shining.

Peduncle of petiole about 0.8× as long as petiolar node, anteroventral margin with broad, rounded process that narrows then usually continues posterad to near posteroventral margin of petiolar node. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface shorter than posterior surface, apex subangulate to angulate. In dorsal view, petiolar node longer than wide, widest near spatulate anterior margin, narrowing posterad. Sides and posterior surface of petiolar node with weakly irregular to irregular, transverse, arcuate, or oblique rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing anterad, maximum width and length about equal. Wavy to irregular rugae on dorsum of postpetiole; rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae on both surfaces weakly granulate-punctate, weakly shining to smooth and shining. Striae extend over anterior one-half or more of first gastral tergum; posterolateral margins and other areas lacking striae moderately to strongly coriarious, dull to weakly shining.

Erect, short to medium length, white pilosity moderately abundant on head, mostly similar in length with up to several longer hairs. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent cream colored to light yellowish setae. Mesosoma, petiolar node, postpetiole, gastral terga with erect, moderately dense, white setae that are similar in length, length of longest hairs on mesosoma approach MOD. Head dark reddish to reddish-brown; dorsum of promesonotum and some to all of first gastral tergum dark reddish-black to black, more posterior terga brown to black; rest of body blackish to black ( Figure 56 ).

Queen diagnosis. Queens of this species are diagnosed by the following combination of features: (1) striae extend over more than anterior one-half of first gastral tergum, (2) in profile, posterolateral and lateral margins of first gastral tergum with striae or moderately to strongly coriarious, weakly shining to dull, (3) in profile, striae visible over extensive parts of more medial portions of segment, (4) large (HW = 1.87–2.49 mm; PNW = 1.34–1.80 mm; ML = 2.34–3.17 mm), (5) superior propodeal spines consist of denticles to minute, blunt teeth, (6) inferior propodeal spines wider than tall, weakly rounded to acuminate, height usually greater than length of superior spines, (7) head dark reddish to reddish-brown, (8) mesoscutum, mesoscutellum concolorous orangish or dark reddish to reddishbrown; pronotum, anepisternum blackish to black, (9) in profile, gaster blackish to black, and (10) mandibles with six to seven teeth ( Figures 2E–F & 57 ).

Measurements —(n = 12 paratypes). HL 1.76–2.00; HW 1.92–2.31; MOD 0.37–0.48; OMD 0.42–0.53; SL 1.25–1.60; PNW 1.50–1.80; HFL 1.77–2.26; ML 2.34–3.04; PW 0.51–0.65; PPW 0.77–0.91. Indices: SI 60.68– 73.08; CI 103.78–120.54; OI 18.59–23.19; HFI 89.86–100.50.

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 wider than long (CI = 103.78–120.54), broadest just posterior to eyes, posterior margin flat to weakly convex. Longitudinal rugae on cephalic dorsum prominent; in full-face view, medial rugae diverging or not diverging toward posterior corners of head; posterior corners rugose, interrugae on cephalic dorsum and posterior corners moderately to strongly granulate-punctate, dull to weakly shining. Mandibles with six (n = 5) or seven (n = 9) teeth, dorsal surface coarsely rugose. Psammophore well developed.

All mesosomal surfaces except pronotal sides with subparallel-parallel, regular to wavy rugae, rugae irregular to rugoreticulate on pronotal sides; interrugae weakly to moderately granulate-punctate, weakly shining to weakly dull; superior propodeal spines consist of denticles to minute, blunt teeth, length less than width at base. Inferior propodeal spines wider than tall, weakly rounded to acuminate, height usually greater than length of superior spines. Peduncle of petiole long, anteroventral margin angles downward then continues posterad parallel to dorsal margin. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex angulate. Posterior surface of petiolar node with wavy, transverse to oblique rugae, interrugae weakly granulate-punctate, weakly shining. In dorsal view, postpetiole slightly wider than long; dorsum with wavy, transverse rugae that are finer, denser than those on posterior surface of petiolar node, interrugae weakly granulate-punctate, weakly shining. Striae extend over more than anterior one-half of first gastral tergum; in profile, posterolateral and lateral margins of first gastral tergum with striae or moderately to strongly coriarious, weakly shining to dull; in profile, striae visible over extensive parts of more medial portions of segment. Most body surfaces with moderately abundant suberect to erect, short to medium length, whitish to cream colored setae, longest hairs on dorsum of mesosoma approximately 0.7–0.8× MOD. Head reddish to reddish-brown; mesoscutum, axilla, mesoscutellum, mesonotum concolorous with head to slightly darker; first gastral tergum dark reddish-black to blackish-red; rest of body black ( Figures 2E–F & 57 ).

Male. Unknown.

Additional material examined. ARGENTINA: Neuquén: Ruta Zapala-Las Lajas , Jan 28, 1999 ( IFML) ( Figure 51C ) .

Etymology. The specific epithet, mapuche , is a noun in apposition and invariant in form that is derived from a group of Indians that lived in this region of Argentina.

Discussion. Pogonomyrmex mapuche is separated from most congeners by: (1) striae extend over anterior onehalf or more of first gastral tergum, posterior margin with striae or moderately to strongly coriarious, and posterolateral margins moderately to strongly coriarious, weakly shining to dull. These characters separate P. mapuche from all but three congeners: P. carbonarius , P. propinqua , and P. weiseri . Pogonomyrmex mapuche is separated from P. propinqua and P. weiseri based on: (1) head dark red to reddish-black; rest of body black or with blackish-red gaster, (2) for all workers in a series, superior propodeal spines consist of tubercles or denticles, rarely short, acuminate teeth, and (3) mandibles with seven teeth for some to most workers in a series. In P. propinqua and P. weiseri : (1) head and gaster are ferruginous orange; mesosoma black, (2) for most workers in a series, the superior propodeal spines are long, length usually> 0.4–0.6× the distance between their bases, and (3) mandibles with six teeth.

Pogonomyrmex mapuche is separated from P. carbonarius by: (1) head dark red to reddish-black; rest of body black or with blackish-red gaster, (2) for all workers in a series, superior propodeal spines consist of tubercles or denticles, rarely short, acuminate teeth, and (3) height of inferior propodeal spines similar to or greater than length of superior propodeal spines. In P. carbonarius : (1) head and/or gaster is usually orangish to orangish-black, (2) for at least some workers in a series, superior propodeal spines long, length> 0.4–0.6× the distance between their bases, and (3) height of inferior propodeal spines usually less than length of superior propodeal spines.

Biology. Pogonomyrmex mapuche workers are solitary foragers. Nests were located by baiting workers with cookie crumbs, then following them back to nests. Two nests were observed: one was under a shrub, the other was in a clump of Stipa sp. (Poaceae) . The mating flight was not observed, but dealate queens were walking on the ground during mid-afternoon on January 24, indicating that mating flights occur during the austral summer.

The type colonies of P. mapuche were at an elevation of 850 m. This species occurs in the Patagonian steppe ecoregion, as defined by Olson et al. (2001) ( Figure 51C ).

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 51. Geographic distribution of: (A) Pogonomyrmex loaensis, (B) P. longibarbis, and (C) P. mapuche. The large black circle in each panel denotes the type locality.

FIGURE 56. Photographs of Pogonomyrmex mapuche holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0280988). Photographs by Estella Ortega from www.AntWeb.org.

FIGURE 57. Photographs of Pogonomyrmex mapuche paratype dealate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0280985). Photographs by Estella Ortega from www.AntWeb.org.