Pogonomyrmex maulensis, 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 : 123-129

Pogonomyrmex maulensis NEW SPECIES

( Figures 58–60 )

Distribution—61A

Holotype worker [ MNNC: CASENT0914363 ]: CHILE, Maule: Talca Province, Rt 115 at W side Laguna del Maule, 36º01.0’S 70º33.6’W, 7180’ (2175 m), 3 March 2014 (R.A. Johnson #5257) . Paratypes, same data as holotype: IFML (9 workers) , LACM (9 workers) , MACN (12 workers) , MCZC (9 workers) , MNNC (12 workers) , RAJC (22 workers, 14 alate queens, 21 males), UCDC (3 workers) , USNM (9 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) first gastral tergum lacking striae, (2) head and gaster orangish-brown to reddish-brown, pronotum reddish-brown to reddish-black, posterior portion of mesopleura and propodeum usually reddish-black, sometimes blackish to black, (3) promesonotal suture usually absent, pronotum and mesonotum concolorous along their juncture, (4) for most to all workers in a series, medial portion of clypeus notably darker (usually reddish-black to black) than adjoining cephalic dorsum, (5) antennal scapes and legs blackish to black, (6) transverse rugae on posterior surface of petiolar node and dorsum of postpetiole, and (7) superior propodeal spines long, length> 0.6–0.8× the distance between their bases ( Figure 58 ).

Measurements — holotype (n = 12 paratypes). HL 1.63 (1.59–1.79); HW 1.65 (1.65–1.81); MOD 0.36 (0.34– 0.39); OMD 0.38 (0.35–0.42); SL 1.26 (1.19–1.37); PNW 1.08 (1.06–1.20); HFL 1.66 (1.61–1.90); ML 1.85 (1.77– 2.12); PW 0.45 (0.40–0.48); PPW 0.59 (0.59–0.67). Indices: SI 76.36 (72.12–79.29); CI 101.23 (99.41–106.29); OI 21.82 (20.12–22.54); HFI 100.61 (94.80–104.97).

Description. Head subquadrate to quadrate (CI = 99.41–106.29); posterior margin flat to weakly convex in full-face view. Longitudinal rugae on cephalic dorsum prominent, wavy to irregular; in full-face view, medial rugae diverging toward posterior corners of head. Interrugae on cephalic dorsum strongly granulate, dull, usually with a beaded appearance; posterior corners rugose, interrugae weakly to moderately granulate, weakly shining. Anterior margin of clypeus moderately concave, dorsum with several subparallel, wavy to weakly irregular, 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 teeth; mandibular dorsum coarsely rugose. MOD ranging from 0.20–0.24× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 0.89–1.18× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 72.12–79.29) failing to reach posterior corners by less than width of basal funicular segment. Antennal scapes with longitudinal striae, interstriae weakly to moderately granulate, weakly shining; basal flange well developed with carinate margin. Psammophore well developed.

Mesosomal profile weakly to moderately convex. In dorsal view, humeral shoulders of pronotum enlarged, weakly to moderately angulate. All mesosomal surfaces with prominent rugae. Dorsum and sides of pronotum rugoreticulate, wavy to irregular rugae on mesopleura angle posterodorsally. Dorsum of promesonotum with weakly to strongly irregular longitudinal rugae, sometimes weakly to moderately rugoreticulate. Promesonotal suture usually absent. Superior propodeal spines long, length> 0.6–0.8× distance between their bases, connected by well defined keel; irregular, transverse or oblique rugae to coarsely rugoreticulate on dorsum of propodeum. Inferior propodeal spines wider than high, apex weakly to broadly rounded. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma weakly to moderately granulate, weakly shining. Legs weakly coriarious, shining to smooth and strongly shining.

Peduncle of petiole about as long as petiolar node, anteroventral margin usually with weakly to well developed broadly rounded process that continues posterad more or less parallel to dorsal surface of peduncle of petiole. In profile, posterior surface of petiolar node weakly convex; node asymmetrical with anterior surface notably longer than posterior surface, apex angulate to weakly rounded. In dorsal view, petiolar node longer than broad, widest near spatulate anterior margin, slightly narrower posterad. Posterior surface of petiolar node with wavy to irregular transverse rugae to rugoreticulate. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin, maximum width and length about equal. Wavy to irregular transverse rugae on dorsum of postpetiole finer, denser than those on posterior surface of petiolar node; interrugae on both surfaces weakly to moderately granulate, weakly shining. First gastral tergum smooth and shining to moderately coriarious, weakly shining anterad, sculpturing near base sometimes appearing in a longitudinal manner giving the appearance of very faint striae.

Erect, mostly short, whitish pilosity moderately abundant on head. Moderately abundant suberect to decumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to semidecumbent whitish setae. Mesosoma, petiolar node, postpetiole, gastral terga with moderately dense, erect, whitish setae that are longer and coarser (especially on mesosoma) than those on cephalic dorsum; longest hairs about 0.6–0.7× MOD. Head orangish-brown to reddish-black except for blackish to black medial portion of clypeus; pronotum reddish-brown to reddish-black, pronotum and adjoining mesonotum concolorous, posterior portion of mesopleura and propodeum usually reddish-black, sometimes blackish to black; gaster dark ferruginous orange with a transverse blackish band along posterior margin of terga; antennae, legs black; petiolar node, postpetiole dark blackish-red to black ( Figure 58 ).

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 extend over anterior two-thirds or more of medial portion of first gastral tergum, posterolateral margins smooth and shining, (3) transverse rugae cover posterior surface of petiolar node and dorsum of postpetiole, (4) longitudinal rugae on cephalic dorsum posterior to eyes strongly irregular, often with short lateral branches, interrugae strongly granulate, dull, with a beaded appearance, (5) in posterodorsal view, rugae along posterior margin of head and in profile, rugae posterior to eyes moderately to strongly irregular, usually with few short lateral branches, (6) head, mesoscutellum concolorous reddish-orange to reddish-brown, (7) anterior and posterolateral portions of mesoscutum usually blackish to black, weakly to notably darker than rest of mesoscutum, which is reddish-orange to reddish-brown, and (8) part to most of anepisternum and/or katepisternum blackish to black ( Figure 59 ).

Measurements —(n = 12). HL 1.71–1.84; HW 1.76–1.93; MOD 0.35–0.41; OMD 0.34–0.44; SL 1.27–1.40; PNW 1.39–1.56; HFL 1.74–1.95; ML 2.37–2.69; PW 0.52–0.58; PPW 0.71–0.80. Indices: SI 65.80–75.27; CI 102.72–110.92; OI 18.62–21.58; HFI 91.58–103.19.

Description. With caste-specific morphology of the mesosoma related to wing-bearing and presence of small ocelli on head. In full-face view, head subquadrate to wider than long (CI = 102.72–110.92), broadest just posterior to eyes, posterior margin flat to weakly convex. Longitudinal rugae on cephalic dorsum prominent, wavy to irregular, rugae posterior to eyes strongly irregular, often with short lateral branches; in posterodorsal view, rugae along posterior margin of head and in profile, rugae posterior to eyes moderately to strongly irregular, but usually with few short lateral branches; in full-face view, medial rugae continuing to posterior margin, interrugae strongly granulatepunctate, dull, with a beaded appearance; posterior corners rugose, interrugae weakly to strongly granulate, weakly shining to dull. Mandibles with six teeth, dorsal surface rugose. Psammophore moderately well developed.

All mesosomal surfaces except pronotal sides with regular to wavy, subparallel rugae, rugae irregular to rugoreticulate on pronotal sides, interrugae weakly to moderately granulate-punctate, weakly shining; superior propodeal spines moderately long, length about 0.3–0.5× the distance between their bases, acuminate; inferior propodeal spines moderately well developed, wider than tall, apex subangulate to angulate. Peduncle of petiolar node long, anteroventral surface with a weakly developed process that narrows posterad and continues to posterior margin. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex subangulate to angulate. Posterior surface of petiolar node with wavy, transverse, oblique, or longitudinal rugae. In dorsal view, postpetiole slightly wider than long; dorsum with wavy to irregular, transverse rugae that are finer, denser than those on posterior surface of petiolar node; interrugae on posterior surface of petiolar node and dorsum of postpetiole weakly granulate-punctate, weakly shining to smooth and shining. Striae extend over anterior two-thirds or more of medial portion of first gastral tergum, posterolateral margins smooth and shining. Most body surfaces with moderately abundant suberect to erect, medium-length, whitish to cream-colored setae. Head, pronotum, mesoscutellum, concolorous reddish-orange to reddish-brown; mesoscutum concolorous reddish-orange to reddish-brown, except for blackish to black promesonotal suture; part to most of anepisternum and/or katepisternum blackish to black ( Figure 59 ).

Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) first gastral tergum lacking striae, (2) bicolored: head and mesosoma black, gaster ferruginous orange, (3) erect hairs lacking on first gastral tergum, (4) anterior portion to all of anepisternum and katepisternum smooth and shining, (5) posterior surface of petiolar node mostly smooth and shining, (6) dorsum of postpetiole with faint, regular, transverse or longitudinal rugae, interrugae mostly smooth and shining, and (7) interrugae on mesoscutum and mesoscutellum weakly granulate, weakly shining to smooth and shining ( Figure 60 ). Note that no characters were found to separate males of P. maulensis and P. araucania .

Measurements —(n = 12). HL 1.28–1.40; HW 1.30–1.44; MOD 0.47–0.55; OMD 0.19–0.25; SL 0.33–0.51; HFL 1.62–1.83; ML 2.35–2.57; PW 0.53–0.63; PPW 0.67–0.79. Indices: SI 24.26–36.96; CI 94.20–104.35; OI 34.78–39.23; HFI 121.58–136.57.

Additional material examined. CHILE: Maule: Rt 115 at 27.8 km W Paso Pehuenche, 6440’ ( RAJC) ( Figure 61A ) .

Etymology. The specific epithet, maulensis , is derived from type series being collected in the Maule Region of Chile.

Discussion. Pogonomyrmex maulensis is not known to co-occur with any congeners. Pogonomyrmex intermedia and P. santschii are the only species that might be confused with P. intermedia . Pogonomyrmex maulensis is separated from P. intermedia based on: (1) for most to all workers in a series, medial portion of clypeus notably darker (usually blackish to black) than adjoining cephalic dorsum, (2) legs and antennal scapes black, and (3) posterior portion of mesopleura and propodeum usually reddish-black, sometimes blackish to black. In P. intermedia : (1) medial portion of clypeus concolorous to adjoining cephalic dorsum, (2) legs and antennal scapes usually orangish-brown, occasionally brownish to blackish, and (3) mesosoma concolorous ferruginous orange to reddish-brown to reddish-black or posterior portion of mesopleura and propodeum blackish to black. Pogonomyrmex maulensis is separated from P. santschii based on: (1) pronotum to entire mesosoma ferruginous orange to reddish-brown or reddish-black. In P. santschii : (1) mesosoma black, occasionally with a weak orangish to reddish infusion on pronotum, infusion rarely present on mesonotum.

Biology. Pogonomyrmex maulensis workers are solitary foragers. The only nest that was observed had two entrances at the edge of a stone. Partial nest excavations indicated the nest contained up to 2000–3000 workers. A mating flight was observed during mid-afternoon on 3 March, indicating that mating flights occur during the austral summer.

Pogonomyrmex maulensis appears to be a mid-elevation species that is known from only two locales near Río Maule at elevations of 1950–2175 m. The type nest was in a Stipa sp. (Poaceae) grassland with scattered Berberis sp. (Berberidaceae) in sandy-rocky soil, the other nest was in a Stipa grassland. This species occurs in the Valdivian temperate forests ecoregion, as defined by Olson et al. (2001) ( Figure 61A ).

Figures

FIGURE 58. Photographs of Pogonomyrmex maulensis holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914363). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 59. Photographs of Pogonomyrmex maulensis paratype alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914365). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 60. Photographs of Pogonomyrmex maulensis paratype male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0914366). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 61. Geographic distribution of: (A) Pogonomyrmex maulensis, (B) P. meridionalis, and (C) P. pichachen. The large black circle in each panel denotes the type locality.