Pogonomyrmex tafi, 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 : 195-201

Pogonomyrmex tafi NEW SPECIES

( Figures 3E–F , 10G , 97–99 )

Distribution—100A

Holotype worker [ MACN: CASENT0235307 ]: ARGENTINA, Tucumán: Departamento Tafi de Valle , 2.2 km N El Infiernillo, 26º44.3’S, 65º46.9’W, 9920 feet (3005 m), 18 January 2010 (R.A. Johnson #4331) . Paratypes, same data as holotype: IFML (3w), MACN (6w), LACM (3w), MCZ (6w), USNM (3w), RAJC (11w, 1dq, 12m), UCDC (3w). Additional paratype series from the same locality and date or on 26 January 2010 —RAJ #4330: RAJC (1 dq); RAJ #4332: RAJC (4w); RAJ #4333: IFML (3w), MACN (3w), MCZ (6w), RAJC (6w); RAJ #4334: MACN (9w), RAJC (12w); RAJ #4336: MACN (3W), RAJC (9w); RAJ #4337: IFML (3w), MACN (3w), RAJC (6w); RAJ #4358: MACN (3W), RAJC (5w, 2m) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) striae extend over anterior two-thirds or more of medial portion of first gastral tergum, posterolateral margins mostly smooth and shining, (2) rugae on dorsum of promesonotum strongly irregular, often becoming rugoreticulate on pronotum, (3) dorsum of pronotum notably darker than adjoining mesonotum, (4) head ferruginous orange, rest of body mostly blackish to black except for an orangish infusion on dorsum of mesonotum and sometimes anterior portion of mesopleura, and (5) rugae on mesopleura wavy to irregular, usually with numerous lateral branches that often connect with adjacent rugae ( Figures 10G , 97 ).

Measurements — holotype (n = 12 paratypes). HL 1.28 (1.54-1.62); HW 1.62 (1.50-1.62); MOD 0.33 (0.34- 0.38); OMD 0.38 (0.38-0.45); SL 1.24 (1.11-1.31); PNW 1.09 (0.99-1.11); HFL 1.51 (1.39-1.70); ML 1.93 (1.74- 2.02); PW 0.40 (0.37-0.47); PPW 0.54 (0.52-0.58). Indices: SI 76.54 (72.08-81.01); CI 102.53 (96.77-101.94); OI 20.37 (21.52-23.72); HFI 93.21 (90.26-105.70).

Description. Head subquadrate to quadrate (CI = 96.77–102.53); posterior margin flat in full-face view. Longitudinal irregular rugae on cephalic dorsum prominent, in full-face view, medial rugae not diverging to diverging toward posterior corners of head with one to few irregular to strongly irregular, discontinuous transverse rugae along medioposterior margin in the latter case; interrugae moderately to strongly granulate, dull to weakly shining, with a beaded appearance; posterior corners weakly rugose, interrugae smooth and shining to strongly shining. Clypeus with numerous subparallel, longitudinal rugae. Numerous long, curved, bristle-like, yellowish macrochaetae project from anterior margin of clypeus and ventral side of mandibles. Mandibles with six to seven teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.20–0.24× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 1.02–1.29× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 72.08–81.01) failing to reaching posterior corners of head by width of basal funicular segment. Antennal scapes weakly to moderately striate, interstriae moderately punctate, weakly shining; basal flange moderately well developed with carinate margin. Psammophore well developed.

Mesosomal profile moderately convex; all mesosomal surfaces with prominent, weakly to strongly irregular, subparallel-parallel rugae. In dorsal view, humeral shoulders of pronotum enlarged, strongly angulate. Promesonotal suture usually weakly impressed. Irregular longitudinal rugae on mesonotum, irregular on pronotum to occasionally rugoreticulate-vermiculate anteromedially, lateral rugae diverging toward humeral shoulders of pronotum and continuing in various configurations on pronotal sides; one to several transverse to oblique rugae usually present along anterior margin of pronotum. Wavy to strongly irregular rugae on mesopleura traverse posterad or angle posterodorsally, usually with numerous lateral branches that sometimes connect to adjacent rugae; transverse, oblique, or longitudinal rugae on dorsum of propodeum traverse ventrally or anteroventrally on sides. Superior propodeal spines consist of weakly subangulate to acuminate denticles, small triangular teeth, or moderately long spines, longest spines <0.4× the distance between their bases; spines usually connected by well defined keel. Inferior propodeal spines triangular, wider than high, apex broadly rounded to subangulate, height slightly less than to similar to length of superior spines. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to moderately granulate-punctate, dull to weakly shining. Legs moderately coriarious, weakly shining.

Peduncle of petiole slightly shorter than petiolar node, anteroventral margin with poorly developed broadly rounded process to well developed triangular process, apex broadly rounded. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface longer than posterior surface, apex subangulate to weakly rounded. In dorsal view, petiolar node longer than wide, widest immediately posterior to spatulate anterior margin. Posterior surface of petiolar node with wavy to irregular transverse rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, width and length similar; dorsal surface with weakly to strongly irregular transverse rugae. Rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node, interrugae weakly to moderately punctate, dull to smooth and shining. Striae extend over anterior two-thirds or more of medial portion of first gastral tergum, posterolateral margins smooth and shining to weakly coriarious, weakly shining.

Erect, short to medium length, whitish to yellowish pilosity moderately abundant on head, longest hairs usually along posterior margin, most hairs <0.4× MOD, one to few hairs sometimes reaching 0.7–0.8× MOD. Moderately abundant semidecumbent to decumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent whitish setae. Rest of body with moderately dense, erect, medium length, whitish setae; hairs on mesosoma rarely> 0.6–0.7× MOD. Head dark ferruginous orange to dark reddishorange or orangish-brown except for black mandibles, clypeus, and antennal scapes; mesonotum blackish to black except for an orangish infusion on mesonotum and sometimes anterior one-half of mesopleura; rest of body blackish to black, except for occasional brownish-black posterior gastral terga ( Figures 10G , 97 ).

Queen diagnosis. Queens of this species are diagnosed by the following combination of features: (1) castespecific morphology of the mesosoma related to wing-bearing and presence of ocelli on head, (2) striae cover more than anterior one-half of medial portion of first gastral tergum, (3) in lateral view, posterolateral and lateral margins of first gastral tergum smooth and shining; in lateral view, striae not visible or visible over a very limited part of more medial portions of segment, (4) head ferruginous orange to orangish-brown; mesoscutum, mesoscutellum dark orangish-brown or dark reddish to reddish-brown; pronotum, anepisternum, gaster blackish to black, first gastral tergum often with a weak orangish infusion, (5) relatively small (HW = 1.43–1.87 mm; PNW = 1.15–1.42 mm; ML = 1.89–2.55 mm), (6) cephalic dorsum posterior to ocelli with irregular rugae, often with lateral branches to rugoreticulate, (7) in posterodorsal view, posterior margin of head with up to several transverse, strongly irregular, medial rugae with short lateral branches, and (8) transverse rugae cover posterior surface of petiolar node and dorsum of postpetiole ( Figure 98 ).

Measurements —(n = 1 + 2 paratypes). HL 1.47–1.90; HW 1.48–1.87; MOD 0.29–0.41; OMD 0.31–0.44; SL 0.99–1.31; PNW 1.17–1.40; HFL 1.40–1.84; ML 1.90–2.55; PW 0.43–0.55; PPW 0.60–0.75. Indices: SI 66.89– 70.72; CI 100.68–106.47; OI 19.59–21.58; HFI 90.06–96.84.

Description. With caste-specific morphology of the mesosoma related to wing-bearing and presence of ocelli on head. In full face view, head subquadrate (CI = 100.68–106.47), broadest just posterior to eyes, posterior margin flat. Longitudinal cephalic rugae prominent, wavy to irregular; cephalic dorsum posterior to ocelli with irregular rugae, often with lateral branches to rugoreticulate; in full-face view, medial rugae weakly diverging toward posterior corners of head, in posterodorsal view, posterior margin of head with up to several transverse, irregular rugae; interrugae on cephalic dorsum moderately to strongly granulate-punctate, with a beaded appearance, dull to weakly shining; posterior corners rugose, interrugae moderately granulate-punctate, weakly shining. Mandibles with six teeth, dorsal surface coarsely rugose. Psammophore well developed.

All mesosomal surfaces except pronotal sides with subparallel, regular to wavy rugae, rugae irregular to rugoreticulate-vermiculate on pronotal sides; interrugae weakly to moderately granulate-punctate, weakly dull to weakly shining; superior propodeal spines consist of short, triangular teeth, length similar to or less than width at base; inferior propodeal spines wider than tall, apex broadly rounded. Peduncle of petiole long, anteroventral margin with a weakly to moderately well developed, broadly rounded process. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex of node subangulate to angulate. Posterior surface of petiolar node with wavy to irregular, transverse rugae to partly rugoreticulate. In dorsal view, postpetiole wider than long; dorsum with wavy to irregular, transverse rugae that are finer, denser than those on posterior surface of petiolar node, interrugae on both surfaces weakly granulate-punctate, weakly shining. Striae cover more than anterior one-half of medial portion of first gastral tergum; in lateral view, posterolateral and lateral margins of first gastral tergum smooth and shining; in lateral view, striae not visible or visible over a very limited part of more medial portions of segment. Most body surfaces with moderately abundant suberect to erect, short to long, cream-colored to yellowish setae. Head ferruginous orange to orangish-brown; mesoscutum, axilla, mesoscutellum concolorous to head to orangish-black; gaster orangish-brown or reddish-brown to blackish-red; rest of body blackish to black ( Figure 98 ).

Male diagnosis. Males 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) smaller: HW = 1.16–1.29 mm, PW = 0.41–0.51 mm, PPW = 0.62–0.66 mm, (3) in profile, petiolar node broadly and smoothly rounded, (4) in profile, anepisternum and katepisternum usually granulate or moderately to strongly coriarious, dull to weakly shining, and (5) in profile, posterior surface of petiolar node usually continuous to weakly irregular ( Figure 99 ).

Measurements —(n = 10 paratypes). HL 1.15–1.35; HW 1.16–1.29; MOD 0.38–0.47; OMD 0.17–0.26; SL 0.34–0.47; HFL 1.43–1.63; ML 1.90–2.22; PW 0.41–0.51; PPW 0.62–0.66. Indices: SI 26.98–38.52; CI 85.93– 109.57; OI 30.16–40.52; HFI 115.08–133.61.

Additional material examined. ARGENTINA: Tucumán: Infiernillo, 3100 m & 3200 m, no date (IFML; LACM; MCZC; MZSP) ( Figure 100A ).

Etymology. The specific epithet, tafi , is a noun in apposition and invariant in form that is derived from a small, localized group of Indians that lived in the area that is now Tafi de Valle, Tucumán Province, Argentina.

Discussion. Pogonomyrmex tafi is known only from the type locality, and P. weiseri is the only congener known to occur in nearby areas. These two species are easily separated based on color and rugae pattern on the first gastral tergum. For P. tafi : (1) gaster blackish to black, and (2) posterolateral margins of first gastral tergum smooth and shining, whereas in P. weiseri : (1) gaster ferruginous orange, and (2) posterolateral margins of first gastral tergum usually strongly coriarious, dull to weakly shining. Pogonomyrmex tafi is separated from other altiplano congeners by: (1) irregular rugae on promesonotum, and (2) dorsum and sides of pronotum darker than the adjoining mesonotum and mesopleura. Pogonomyrmex tafi is most likely to be confused is with P. pulchellus given that the dorsum and sides of the pronotum are darker than the adjoining mesonotum and mesopleura in both species. However, rugae on the mesopleura are regular to wavy, and usually lack lateral branches in P. pulchellus , whereas in P. tafi these rugae are wavy to strongly irregular, usually with numerous lateral branches that sometimes connect with adjacent rugae.

Biology. Little is known about the biology of P. tafi . Workers are solitary foragers. Nests were placed in open, exposed sites and consisted of a tumulus up to 10 cm in diameter. Partial nest excavations indicated that colonies contain up to approximately 2000 workers. Sexuals have been collected from January 18–26 indicating that mating flights occur during the austral summer. One intercaste also was collected ( Figures 3E–F ).

Pogonomyrmex tafi is only known from the type locality which is at 3005 m. The type colonies were in an alpine grassland in the Central Andean Puna ecoregion, as defined by Olson et al. (2001) ( Figure 100A ).

Figures

FIGURE 3. Closeup photographs of the mesosoma in dorsal view and in profile of apparent intercastes for Pogonomyrmex: (A–B) P. longibarbis (CASENT0914117), (C–D) P. sanmartini (CASENT0280979), (E–F) P. tafi (LACMENT273737), and (G–H) P. vermiculatus (CASENT0280984). Note the enlarged, convex mesosomas in profile, and the strongly arched mesoscutellum in dorsal view. Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 10. Closeup photographs for workers of Pogonomyrmex showing dorsum of promesonotum with rugae that are well-defined, very regular and continuous, lacking short lateral branches; longitudinal rugae on mesonotum diverging toward humeral shoulders of pronotum; anterodorsal margin of pronotum with one to several straight, strong, continuous, transverse rugae: (A) P. apterogenos holotype worker (CASENT0914124), (B) P. lagunabravensis holotype worker (CASENT0249051), (C) P. longibarbis (CASENT0249056), and (D) P. sanmartini (CASENT0922481), and dorsum of promesonotum with rugae that are usually wavy to irregular, discontinuous or with short lateral branches; rugae on mesonotum mostly longitudinal but often becoming irregular to rugoreticulate on pronotum; anterodorsal margin of pronotum with wavy to irregular rugae to rugoreticulate, usually with short lateral branches: (E) P. RAJ-altip worker (CASENT0235280), (F) P. andinus (CASENT0914130), (G) P. tafi holotype worker (CASENT0235307), and (H) P. sanmartini (CASENT0922479). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 97. Photographs of Pogonomyrmex tafi holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0235307). Photographs by Estella Ortega from www.AntWeb.org.

FIGURE 98. Photographs of Pogonomyrmex tafi paratype dealate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922473). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 99. Photographs of Pogonomyrmex tafi paratype male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0235303). Photographs by Shannon Hartman and Will Ericson from www.AntWeb.org.

FIGURE 100. Geographic distribution of: (A) Pogonomyrmex tafi, (B) P. varicolor, and (C) P. vermiculatus. The large black circle in each panel denotes the type locality.