Pogonomyrmex lagunabravensis, 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 : 96-102

Pogonomyrmex lagunabravensis NEW SPECIES

( Figures 10B , 44–46 )

Distribution—43B

Holotype worker [ MACN: CASENT0249051 ]: ARGENTINA, La Rioja : Departamento Vinchina , Rt 76 at 64.5 km NW Alto Jagüé, 28º26.0’S 68º50.6’W, 12,620’ (3825 m), 2 January 2006 (R.A. Johnson #3739) . Paratypes, same data as holotype: CASC (1 worker, 1 ergatoid queen), IFML (3 workers) , LACM (3 workers) , MACN (13 workers, 2 ergatoid queens), MCZC (3 workers) , RAJC (12 workers, 10 ergatoid queens), UCDC (2 workers) , USNM (3 workers) . Additional paratype series from the same locality and date—RAJ #3737: LACM (3 workers) , RAJC (3 workers) ; RAJ #3738: IFML (3 workers) , MACN (3 workers) , RAJC (6 workers) .

Worker diagnosis. Workers of this species are uniquely characterized by the following combination of features: (1) striae extend over more than anterior one-half of first gastral tergum, posterolateral margins smooth and shining to moderately coriarious, weakly shining, (2) for most to all workers in a series, rugae on dorsum of promesonotum well defined, very regular and continuous, lacking short lateral branches; longitudinal rugae on mesonotum diverging toward pronotal shoulders; anterodorsal margin of pronotum with one to several straight, strong, continuous, transverse rugae, (3) superior propodeal spines consist of tubercles, denticles, or minute teeth (all rounded to blunt tipped), keel connecting superior propodeal spines absent; inferior propodeal spines longer than superior spines, (4) rugae between frontal lobes subparallel-parallel, medial rugae usually continuing onto frontal triangle, (5) head and mesosoma mostly concolorous ferruginous orange to light orangish-black, mesosoma sometimes slightly darker than head ( Figures 10B , 44 ).

Measurements — holotype (n = 12 paratypes). HL 1.60 (1.48–1.73); HW 1.65 (1.45–1.79); MOD 0.35 (0.33– 0.40); OMD 0.39 (0.35–0.48); SL 1.25 (1.00–1.29); PNW 1.08 (0.95–1.15); HFL 1.62 (1.33–1.77); ML 1.83 (1.68– 2.03); PW 0.41 (0.33–0.43); PPW 0.56 (0.51–0.60). Indices: SI 75.76 (65.79–78.21); CI 103.12 (97.32–104.17); OI 21.21 (21.23–24.83); HFI 98.18 (87.50–101.33).

Description. Head subquadrate to quadrate (CI = 97.32–104.17); posterior margin flat to weakly convex in full-face view. Longitudinal rugae on cephalic dorsum prominent, rugae between frontal lobes subparallel-parallel, medial rugae between frontal lobes subparallel-parallel, usually continuing onto frontal triangle. Interrugae on cephalic dorsum moderately granulate-punctate, weakly shining; posterior corners rugose, interrugae weakly granulate, weakly shining to smooth and shining. Anterior margin of clypeus moderately concave, dorsum with numerous subparallel, 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 0.21–0.25× HL. In profile, eyes situated slightly anterior to middle of head, OMD = 0.97–1.27× MOD. In full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI = 65.79–78.21) failing to reach posterior corners of head by about the length of the basal funicular segment. Antennal scapes usually weakly to moderately striate, interstriae weakly to moderately punctate, weakly shining to smooth and shining; basal flange moderately well developed with carinate margin. Psammophore well developed.

Mesosomal profile flat to weakly convex; all mesosomal surfaces with prominent widely spaced, regular, subparallel-parallel rugae. For most to all workers in a series, rugae on dorsum of promesonotum well defined, very regular and continuous, lacking short lateral branches; longitudinal rugae on mesonotum diverging toward humeral shoulders of pronotum; anterior margin of pronotum with one to several straight, strong, continuous, transverse rugae that continue onto pronotal sides. In dorsal view, humeral shoulders of pronotum enlarged, strongly angulate. Promesonotal suture usually present. Regular to weakly irregular rugae on mesopleura angle posterodorsally; regular transverse rugae on dorsum of propodeum traverse ventrally or anteroventrally on sides. Superior propodeal spines consist of tubercles, blunt denticles, or small, blunt, triangular teeth. Inferior propodeal spines wider than high, triangular, apex broadly rounded to acuminate, height 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 moderately coriarious, weakly shining to smooth and shining.

Peduncle of petiole about as long as petiolar node, anteroventral margin with a weakly to well developed broadly rounded process. 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, sides subparallel anterad, slightly narrower posterad, anterior margin broadly rounded. Sides and posterior surface of petiolar node with regular, transverse rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing anterad, maximum width and length similar; transverse to weakly arcuate rugae posterad, anterad rugae traversing medially from lateral margin then curving anteriorly to become longitudinal; anterolateral rugae concentric, curving from lateral to anterior margin, or rarely with all anterad rugae transverse or weakly arcuate; rugae on dorsum of postpetiole finer, denser that those on posterior surface of petiolar node; interrugae on both surfaces weakly granulate, weakly shining to smooth and strongly shining. Striae extend over more than anterior one-half of first gastral tergum, often extending to posterior margin or posterior margin moderately to strongly coriarious, dull to weakly shining; posterolateral margins smooth and shining to moderately coriarious, weakly shining.

Erect, mostly short to medium length, yellowish pilosity moderately abundant on head, no hairs exceed about 0.7× MOD. Moderately abundant suberect to semidecumbent pilosity on scape; abundant decumbent hairs on funicular segments. Legs with moderately abundant suberect to decumbent yellowish setae. Rest of body with moderately dense, erect, medium-length, yellowish setae. Head light to dark ferruginous orange to dark red-orange; mandibles, antennae, clypeus, frontal lobes, anterior margin of head, petiolar node, postpetiole dark blackish-orange to blackish; mesosoma dark ferruginous orange, usually slightly darker than head; gastral terga light to dark orangish-black, often with darker transverse black band along posterior margins ( Figures 10B , 44 ).

Queen diagnosis. Queens of this species are diagnosed by the following combination of features: (1) ergatoid, (2) first gastral tergum with fine longitudinal striae, silky in appearance, (3) anterior margin of clypeus entire, and (4) in dorsal view, pronotum and mesoscutum weakly differentiated, mesoscutum with longitudinal rugae, pronotum with transverse rugae ( Figure 45 ).

Measurements —(n = 12 paratypes). HL 1.75–1.83; HW 1.77–1.89; MOD 0.39–0.45; OMD 0.41–0.50; SL 1.18–1.34; PNW 1.16–1.25; HFL 1.66–1.80; ML 2.08–2.20; PW 0.43–0.51; PPW 0.68–0.74. Indices: SI 64.48– 73.63; CI 99.44–104.00; OI 22.03–24.73; HFI 90.22–98.36.

Description. Ergatoid; in full face view, head quadrate to subquadrate (CI = 99.44–104.00), posterior margin flat. Cephalic dorsum with wavy, longitudinal rugae, medial rugae diverging toward posterior corners along posterior margin, interrugae moderately granulate-punctate, weakly shining. Posterior margins rugose, interrugae smooth and shining. Mandibles with six teeth, dorsal surface coarsely rugose. Psammophore well developed.

Mesosoma lacking all morphological structures related to or for inserting wings; all mesosomal surfaces with subparallel, wavy rugae; interrugae smooth and shining to moderately granulate-punctate, weakly shining. Pronotum large with wavy, transverse rugae that traverse ventrally on pronotal sides. Mesoscutum reduced in size, not extending to pronotal collar; sides subparallel, converging to bluntly acuminate to arcuate anterior margin. Dorsum of propodeum transversely rugose; superior propodeal spines reduced to denticles or small teeth; inferior propodeal spines well developed, height greater than that of superior spines, triangular, apex acuminate. Peduncle of petiole long, anteroventral margin with a weakly to well developed rounded process. In profile, petiolar node asymmetrical with anterior surface shorter than posterior surface, apex subangulate to angulate. Postpetiole convex in profile; in dorsal view, maximum width about equal to length. Posterior surface of petiolar node and dorsum of postpetiole with wavy, transverse rugae; interrugae weakly punctate, weakly shining to shining. Striae extend over more than anterior one-half of first gastral tergum, often extending to posterior margin or posterior margin moderately to strongly coriarious, dull to weakly shining; posterolateral margins smooth and shining to moderately coriarious, weakly shining. Most body surfaces with moderately abundant suberect to erect, short, white to cream-colored setae, longest hairs on posterior terga. Head, pronotum, mesoscutum, first gastral tergum ferruginous orange; anterior margin of head, clypeus, frontal lobes, mandibles, antennae, legs, petiolar node, postpetiole black; pronotal collar, sides of pronotum, propodeum blackish, sometimes with an orangish infusion ( Figure 45 ).

Male diagnosis. Males of this species are diagnosed by the following combination of features: (1) ergatoid, (2) in profile, cephalic rugae forming circumocular whorls posterior to eyes, and (3) notauli present ( Figure 46 ).

Measurements —(n = 1). HL 1.38; HW 1.43; MOD 0.42; OMD 0.24; SL 0.55; HFL 1.61; ML 1.92; PW 0.44; PPW 0.63. Indices: SI 38.46; CI 103.62; OI 29.37; HFI 112.59.

Additional material examined. ARGENTINA: La Rioja : 55.3 km NW Alto Jagüe, 11,430’, Jan 16, 2010 (RAJC); 63.0 km NW Alto Jagüe, 12,900’, Jan 16, 2010 (RAJC); Refugio de Peñon, no date (IFML) ( Figure 43B ).

Etymology. The specific epithet, lagunabravensis , is derived from this species occurring near Reserva Laguna Brava, La Rioja Province, Argentina.

Discussion. Pogonomyrmex lagunabravensis is not known to co-occur with any congeners, but it is similar to several high-elevation (> 3000 m) species in which the first gastral tergum is striate and longitudinal rugae on the promesonotum are very regular, subparallel-parallel. These similar species include P. apterogenos , P. longibarbis , P. pulchellus , and P. rastratus . Pogonomyrmex lagunabravensis can be distinguished from P. apterogenos based on: (1) medial rugae on the cephalic dorsum are subparallel-parallel and continue onto the clypeus, and (2) the superior propodeal spines reduced to minute, rounded denticles or tubercles. In P. apterogenos : (1) medial rugae on cephalic dorsum not subparallel-parallel, but rather they converge and end near the posterior margin of clypeus, and (2) superior propodeal spines consist of acuminate denticles, small triangular teeth, or rarely short spines. Pogonomyrmex lagunabravensis is separated from P. longibarbis by: (1) superior propodeal spines consist of tubercles, denticles, or minute teeth (all rounded to blunt tipped) with inferior propodeal spines longer than superior spines, and (2) keel connecting superior propodeal spines absent. For P. longibarbis : (1) superior propodeal spines consist of minute teeth, short triangular teeth, or short spines (all acuminate) with inferior propodeal spines shorter than to as tall as superior spines, and (2) keel connecting superior propodeal spines well developed. Pogonomyrmex lagunabravensis is distinguished from P. pulchellus based on: (1) superior propodeal spines consist of tubercles, denticles, or minute teeth (all rounded to blunt tipped), (2) inferior propodeal spines longer than superior spines, (3) keel connecting superior propodeal spines absent and (4) dorsum of pronotum concolorous with adjoining mesonotum. For P. pulchellus : (1) superior propodeal spines consist of minute teeth, short triangular teeth, or short spines (all acuminate), (2) inferior propodeal spines shorter than to as tall as superior spines, (3) keel connecting superior propodeal spines well developed, and (4) dorsum of pronotum darker than with adjoining mesonotum. Pogonomyrmex lagunabravensis is distinguished from P. rastratus based on: (1) superior propodeal spines consist of tubercles or denticles to rarely short spines (all rounded to blunt tipped) with inferior propodeal spines longer than superior propodeal spines. For P. rastratus : (1) superior propodeal spines consist of short triangular teeth to long spines, and (2) inferior propodeal spines shorter than superior propodeal spines.

In his description of P. andinus, Kusnezov (1951) listed two localities, San Antonio de los Cobres, Salta Province (designated as the type locality), and Refugio del Peñón, La Rioja Province, Argentina. The latter site is 2–3 km from the type locality for P. lagunabravensis , and the three workers referred to by Kusnezov (F. Monrós coll., [IFML]) were determined to be P. lagunabravensis .

Biology. Little is known about the biology of P. lagunabravensis . Type nest series were in deep sandy-silty soil with Stipa sp. (Poaceae) as the dominant plant. Nests most commonly were placed in a clump of Stipa sp. or at the edge of a stone. Nests were most easily located by baiting workers with cookie crumbs, then following them back to the nest. The nest entrance consists of a hole in the ground or with a tumulus up 15 cm in diameter. Ergatoid queens and ergatoid males have been collected from January 2–16, indicating the mating flights occur during the austral summer. Pogonomyrmex lagunabravenesis is most closely related to P. apterogenos , and both species are unique among ants because they are the only species known to have ergatoid queens and ergatoid males.

Pogonomyrmex lagunabravensis inhabits sites at elevations from 3465–3910 m in the Central Andean puna ecoregion, as defined by Olson et al. (2001) ( Figure 43B ).

Figures

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 43. Geographic distribution of: (A) Pogonomyrmex intermedia, (B) P. lagunabravensis, and (C) P. leonis. The large black circle in each panel denotes the type locality.

FIGURE 44. Photographs of Pogonomyrmex lagunabravensis holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0249051). Photographs by Will Ericson from www.AntWeb.org.

FIGURE 45. Photographs of Pogonomyrmex lagunabravensis paratype ergatoid queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0173126). Photographs by April Nobile from www.AntWeb.org.

FIGURE 46. Photographs of Pogonomyrmex lagunabravensis ergatoid male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0249058). Photographs by Will Ericson from www.AntWeb.org.