Pogonomyrmex hoelldobleri Johnson, Overson & Moreau, 2013

Johnson, Robert A., Overson, Rick P. & Moreau, Corrie S., 2013, A New Species of Seed-harvester Ant, Pogonomyrmex hoelldobleri (Hymenoptera: Formicidae), from the Mohave and Sonoran Deserts of North America, Zootaxa 3646 (3), pp. 201-227 : 213-217

Pogonomyrmex hoelldobleri Johnson, Overson & Moreau , NEW SPECIES

( Figures 2 , 6–8 )

Pogonomyrmex magnacanthus Cole, 1968: 133 [part].

Worker

Diagnosis. Pogonomyrmex hoelldobleri is characterized by: (1) eye not unusually large (MOD usually <0.42, OI usually <27.50, MR usually> 1.05 ( Figure 3 ), (2) mandible with seven teeth, (3) cephalic rugae converge posterior to eyes, usually near vertex, but not forming circumocular whorls, (4) interrugal spaces on pronotal sides moderately to strongly granulate, dull to weakly shining (see Figures 2 , 6 ), and (5) gaster concolorous with head and mesosoma.

Measurements (mm)— holotype (n = 75 [15 paratypes, 43 non-types, 16 P. magnacanthus Paratypes]). HL 1.57 (1.24–1.76); HW 1.55 (1.17–1.84); MOD 0.36 (0.30–0.42); OMD 0.42 (0.35–0.72); SL 1.20 (0.94–1.34); PNW 0.91 (0.77–1.11); HF 1.67 (1.19–1.89); ML 1.84 (1.35–2.03); PW 0.34 (0.27–0.46): PPW 0.51 (0.38–0.59). Indices: SI 77.42 (66.25–87.18); CI 98.73 (93.98–115.79); OI 23.23 (21.12–29.01); HFI 107.74 (84.97–117.93).

Description. Head subquadrate to quadrate (CI = 93.98–115.79), broadest just posterior to eye; posterior margin flat in full-face view. Longitudinal cephalic rugae prominent, in full-face view median rugae usually diverging toward posterior corners near posterior margin of head. In side view, rugae converging slightly near vertex, occasionally becoming faint between posterior margin of eye and vertex. Vertex faintly to strongly rugose, occasionally mostly smooth to weakly granulate, sub-shining to shining. Cephalic interrugal spaces moderately punctate, sub-shining to smooth and shining. Anterior margin of clypeus slightly concave. Mandible with seven teeth; mandibular dorsum coarsely striate. In profile, eyes not unusually large, MOD ranging from 0.22–0.29x HL, OI = 21.12–29.01, MR usually> 1.05; eye situated near middle of head. Antennal scapes moderately long (SI = 66.25–87.18), failing to reach vertex by less than length of basal funicular segment. Basal flange of antennal scape flattened and well developed, margin weakly carinate. Psammophore well developed.

Mesosomal profile convex. All mesosomal surfaces with prominent parallel/subparallel rugae. Dorsum of promesonotum with transverse rugae that curve obliquely to posterior on pronotal sides, rugae on pronotal sides often slightly less distinct than on other portions of mesosoma; rugae usually oblique to longitudinal on anterior portion of mesonotum. Mesopleura with subparallel rugae angling posterodorsally. Propodeum lacking spines or teeth; in side view, juncture of propodeum and propodeal declivity evenly convex to weakly angulate; rugae on propodeal dorsum transverse, declivitous face smooth and shining. Propodeal spiracles narrowly ovate. Interrugal spaces on mesosoma moderately granulate-punctate, sub-shining to smooth and shining; interrugal spaces on pronotal sides usually more densely granulate than other portions of mesosoma. Legs moderately to strongly shining.

Petiolar peduncle long, ventral margin straight. In side view, posterior face of petiole slightly convex; petiolar node asymmetrical with anterior surface slightly shorter than posterior surface. Apex of node weakly to strongly angulate, posterior surface sometimes curved upward near anterior margin. In dorsal view, petiolar node longer than broad, sides subparallel or diverging slightly toward the smoothly rounded to weakly angulate anterior margin. Sides and dorsum of petiolar node strongly granulate-punctate, dull to sub-shining to smooth and shining, occasionally with several longitudinal to oblique rugae that are restricted to posterior one-third of petiole. Dorsum of postpetiole convex in profile; in dorsal view, widest at or near posterior margin and tapering to anterior margin, maximal width about equal to length, weakly to moderately granulate, dull to sub-shining. Gaster smooth and strongly shining.

Erect to suberect white pilosity moderately abundant on head, short to medium in length, often with one to few longer hairs, none exceeding MOD. Moderately abundant semidecumbent to decumbent pilosity on scape, abundant semidecumbent to decumbent hairs on funicular segments. Legs with moderately abundant suberect to semidecumbent white setae. Mesosoma, petiole, and postpetiole with a lower density of mostly longer, flexuous hairs mostly concentrated on dorsal surface, longest distinctly shorter than MOD; gastric tergites with moderately abundant, medium length suberect hairs. Entire body concolorous light to dark ferruginous orange, posterior portion of gaster sometimes slightly darker ( Figure 6 ).

Queen

Diagnosis. As in worker diagnosis, but with caste-specific structures related to wing-bearing and presence of small ocelli on head. Mandible with seven teeth. Eye not unusually large (MOD <0.45, OI <28.50, MR usually> 1.05). All mesosomal surfaces except for mesoscutum and mesoscutellum with prominent rugae; sculpturing absent on mesoscutum and mesoscutellum except for scattered punctures and occasional faint longitudinal striae ( Figure 7 ). Posterior face of petiole and dorsum of postpetiole weakly to moderately granulate or with weak tranverse rugae. Base of scape rounded; superior and inferior lobes poorly developed, no wider than width of scape base.

Measurements (mm)—(n = 8). HL 1.36–1.66; HW 1.44–1.79; MOD 0.40–0.45; OMD 0.40–0.50; SL 0.97– 1.23; PNW 1.24–1.54; HFL 1.38–1.67; ML 2.18–2.62; PW 0.45–0.57; PPW 0.61–0.73. Indices: SI 65.52–72.12; CI 100.00–114.10; OI 22.47–28.47; HFI 83.64–109.03.

Description. As in worker diagnosis, but with caste-specific structures related to wing-bearing, presence of small ocelli on head, and as illustrated in Figure 7 . Small, only slightly larger than conspecific workers. In full-face view, head quadrate to broader than long, posterior margin flat. Dorsum and sides of head conspicuously rugose, in side view rugae forming circumocular whorls posterior to eyes or rugae converging near vertex, interrugal spaces smooth and strongly shining. Mandible with seven teeth, dorsal surface coarsely rugose, strongly shining. Eyes not large (OI = 22.47–28.47), MR usually> 1.05, MOD ranging from 0.25–0.30x HL. Base of scape not flattened; superior and inferior lobes poorly developed, no wider than width of base of scape.

Mesosoma as described above, propodeum unarmed; in side view, juncture of propodeum and propodeal declivity rounded to subangulate, sides and dorsal surface rugose or rugae absent near mid-line, shining, posterior surface smooth and strongly shining. Petiolar peduncle long, ventral margin straight. In side view, petiolar node asymmetrical with anterior surface shorter than posterior surface. Apex of node moderately to strongly angulate, anterior edge of posterior face sometimes curved upward forming a crest. Postpetiole broader than long. Posterior face of petiole and dorsum of postpetiole weakly to moderately granulate or with weak transverse rugae, subshining to shining. Gastric tergites smooth and shining. Most body surfaces with moderately abundant coarse suberect to erect setae. Entire body concolorous light to dark ferruginous orange, except for incomplete to complete darker transverse bands on one or more gastric tergites.

Male

Diagnosis. Mandible with four teeth on suboblique cutting margin. Mandibular dorsum, clypeus, and antennal scapes lacking sculpture (mandibular dorsum occasionally with faint striae), mostly smooth and shining except for scattered punctures; anterior margin of clypeus weakly concave, lateral lobes indistinct. Eye not unusually large (MOD <0.50, OI <39.4, MR> 0.38) ( Figure 8 ).

Measurements (mm)—(n = 2). HL 1.15–1.25; HW 1.27–1.30; MOD 0.49–0.50; OMD 0.19–0.20; SL 0.54– 0.56; HFL 1.43–1.56; ML 2.08–2.26; PW 0.54–0.58; PPW 0.65–0.73. Indices: SI 42.52–43.08; CI 104.00–110.43; OI 37.69–39.37; HFI 112.60–120.00.

Description. Mandible with four teeth on suboblique cutting margin; tip of sub-apical tooth sometimes weakly bifid; basal tooth not offset; mandibular dorsum as described above. Anterior margin of clypeus broadly and shallowly concave, mostly smooth and shining except for scattered punctures, lateral lobes indistinct. Antennal scapes reaching to or near posterior margin of eye, mostly smooth and shining. Cephalic rugae fine and close, slightly wavy to irregular, interrugae weakly punctate, moderately shining.

In profile, anterior face of mesonotum forming a mostly straight line with pronotum, slightly less than one-half as long as dorsal surface. In side view, juncture between propodeum and propodeal declivity subangulate, without spines or denticles. Sides of pronotal collar superficially rugoreticulate to punctate-granulate; katepisternum partially to largely covered by very fine wavy to irregular longitudinal striae, sub-shining to shining. Mesonotum shiny with piligerous punctures, notauli weakly impressed. Propodeum mostly smooth and shining to microrugoreticulate, granulate, sub-shining. Ventral margin of petiolar peduncle straight. In side view, petiolar node broadly rounded, anterior surface longer than posterior surface, forming a mostly straight continuous to slightly curved profile with dorsal surface of petiolar peduncle. Dorsal surface of petiole smooth and shining with scattered punctures to microrugoreticulate, sub-shining. Postpetiole broader than long, dorsal surface mostly smooth, sub-shining to shining. Head, mesosoma, petiole, and postpetiole with moderately abundant flexuous white hairs, often similar in length to MOD. Gastric tergites smooth and shining, hairs shorter and less dense than on rest of body. Head and mesosoma brownish-orange, gaster a lighter ferruginous orange ( Figure 8 ).

Type material: Holotype (worker) plus 27 paratypes. UNITED STATES: Arizona: Yuma Co. : 0.2 km S Tacna, 125 m (22o 6.4’S 65o 36.8’W), May 14, 2010, leg. R.A. Johnson #4500. Nests were in Sonoran Desert habitat that was dominated by scattered individuals of Larrea tridentata and Ambrosia dumosa . The holotype is deposited in the MCZ. Paratypes (n = 27 workers) all from the same locality and date as the holotype and leg. R.A. Johnson #4500 are distributed as follows: MCZ (6w), LACM (3w), UCDC (3w), USNM (6w), WPMC (3w), RAJC (6w). Additional paratype series (RAJC), collected on June 24, 2009, include RAJ #4253 (6w) and RAJ#4255 (9w): all series have additional workers in ethanol.

Additional material examined. UNITED STATES: Arizona: Maricopa Co.: 12 mi E Sentinel, Jul 30, 1960, AC Cole AZ-519 (26w PARATYPES of P. magnacanthus , LACM). Mohave Co.: Golden Shores, Sep 5, 1995, RA Johnson RAJ#691 (8w, RAJC); 0.3 mi W Golden Shores, May 18, 2010, 620’, RA Johnson RAJ#4490 (6w, RAJC). Yuma Co. : I-8 at Aztec Road, 490’, Apr 26, 2012, RA Johnson #4919 (6w, RAJC). California: Imperial Co. : Coyote Wells, Jul 29, 1957, AC Cole CAL-305 (17w, LACM); El Centro to Jacumba, Jul 10, 1956, AC Cole CAL-11 (3w PARATYPES of P. magnacanthus , LACM), CAL-12 (3w PARATYPES of P. magnacanthus , LACM); 14 mi W Winterhaven, Jul 28, 1959, AC Cole CAL-334A (6w PARATYPES of P. magnacanthus , LACM); 15 mi E Holtville, Jul 27, 1961, AC Cole CAL-394 (24w PARATYPES of P. magnacanthus , LACM). Inyo Co. : Death Valley National Monument at Ashford Mill, 0’, Apr 28, 1952, WS Creighton no number (16w, 5aq, LACM), CR-226 (10w, 1aq, 1m, LACM), CR-417 (11w, 1aq, LACM), CR-618 (15w, 1aq, 1m, LACM); Death Valley National Park, Spring 2000, KE Anderson KEA#550 (3w, RAJC); 9.05 km W Panamint Springs, 4450', May 30, 2006, RR Snelling #06-006 (1w, RAJC); Riverside Co.: 21 mi E Indio, 1600’, Apr 8, 1952, WS Creighton CR-324 (19w PARATYPES of P. magnacanthus , LACM). San Bernardino Co.: Needles, May 1905, WM Wheeler (3w, LACM); 3.5 mi N Pisgah Crater, 2270’, May 11, 2010, RA Johnson RAJ#4488 (6w, RAJC), RAJ#4489 (6w, RAJC); 5.5 mi NW Pisgah Crater, 1890’, May 4, 2010, RA Johnson RAJ#4493 (3w, RAJC), RAJ#4494 (5w, 1aq, RAJC); I-40 at Goffs Road, 2040’, Sep 16, 2011, RA Johnson RAJ#4808 (6w, RAJC). San Diego Co.: Anza Borrego State Park, Palm Canyon, Apr 17, 1952, WS Creighton CR-559 (6w, LACM); Ocotillo Well, Aug 8, 1960, AC Cole CAL-366 (4w PARATYPES of P. magnacanthus , LACM). Nevada: Clark Co.: 7 mi W Echo Bay, 1800’, Apr 5, 1976, G & J Wheeler NEV-725 (3w, LACM); 4 mi SW Riverside, 1500’, Apr 2, 1970, G & J Wheeler NEV#707 (3w, LACM); 5 km E Jean, Apr 26, 2009, 2780’, RA Johnson RAJ#4222 (3w, RAJC), RAJ#4223 (3w, RAJC); Valley of Fire, 2100’, Mar 14, 1970, G & J Wheeler NEV#640 (3w, LACM), NEV#631 (3w, LACM); Valley of Fire, 2000’, NEV#645 (2w, LACM); W base of Mormon Mesa, 1500’, Apr 3, 1970, G & J Wheeler NEV#720 (3w, LACM), NEV#716 (3w, LACM); 3 mi W Cottonwood Cove, 1200’, Dec 10, 1970, G & J Wheeler NEV-1498 (3w, LACM). Nye Co.: Mercury, Jul 11, 1961, #5AA1C (1w, LACM), May 24, 1961, #5EA7C (1w, LACM); Pahrump, spring 2000, KE Anderson KEA#532 (3w, RAJC); 2 mi N Pahrump, 2700’, Apr 4, 1970, G & J Wheeler NEV-740 (2w, LACM); Beatty, Jul 17, 1954, AC Cole, NEV-374 (6w, LACM), NEV-375 (4w, LACM), NEV-376 (6w, LACM), NEV-377 (22w, LACM), NEV-380 (2w, LACM); Hwy 95 at 4.0 mi NW Lathrop Wells, 2610’, Apr 17, 2009, RA Johnson RAJ#4216 (6w, RAJC), RAJ#4217 (9w, RAJC); Rock Valley, 9 mi ENE Lathrop Wells, Apr 14, 1970, G & J Wheeler, NEV-781 (9w, LACM). MEXICO: Baja California: Valle San Felipe, May 10, 1998, RA Johnson RAJ#BC 1376 (9w, RAJC), RAJ#BC 1377 (9w, RAJC). Sonora: Pinacate Desert, no date, 1982, IR López Moreno #F-11 (2w, LACM), #F-16 (8w, LACM); Puerto Peñasco, 50’, Jul 15, 1950, WS Creighton #308 (30w, LACM), #304 (3w, LACM); 11.5 mi E Puerto Peñasco, July 17, 2009, RA Johnson RAJ#4274 (9w, RAJC), RAJ#4278 (3w, RAJC), RAJ#4281 (9w, RAJC).

Etymology. The specific epithet honors Prof. Dr. Bert Hölldobler, who was an “ant god” during the tenure of RAJ in graduate school and beyond—and who now is a good friend, colleague, collaborator, and supporter who is dedicated to understanding all aspects of ant biology. His continued child-like enthusiasm for learning about ants and his earnest interest in helping students invigorate all of those around him.

Discussion. Pogonomyrmex hoelldobleri is most likely to be confused with P. magnacanthus , especially given the large number of series that A.C. Cole erroneously identified as P. magnacanthus . The two species occur sympatrically in several locales. The significantly larger eye (MOD and OI) separates P. magnacanthus from P. hoelldobleri ( Figures 2-3 ). OI is the best character to separate the two species because it is consistently higher for P. magnacanthus (OI = 27.22-33.61) than for P. h o e l l d o b l e r i (OI rarely> 27.50)( Figure 3 ). The malar ratio is usually <1.0 for P. magnacanthus , while this ratio is usually> 1.05 for P. hoelldobleri ( Figure 3 ).

Pogonomyrmex hoelldobleri also occurs in sympatry with P. californicus and is likely to occur in sympatry with P. mohavensis , but it has a low likelihood of co-occurring with P. m a r i c o p a. Pogonomyrmex hoelldobleri can be distinguished from P. mohavensis based on the following characters: (1) P. hoelldobleri has seven teeth, (2) the interrugal spaces on the pronotal shoulders are weakly to strongly punctate/granulate, dull to sub-shining, and (3) the cephalic rugae typically converge near the vertex. In P. mohavensis , the mandible has six teeth (a seventh sometimes occurs as a denticle between the basal and sub-basal teeth), interrugal spaces on the pronotal shoulders are smooth and shining, and the cephalic rugae extend more or less directly to the vertex or converge only slightly near the vertex. Two other P. californicus group species ( P. anzensis and P. snellingi ) also occur in the Sonoran and Mohave Deserts, but it is doubtful that P. hoelldobleri occurs sympatrically with either species; P. anzensis occurs in unproductive, rocky hillside habitats unlike any sites that are known to be occupied by P. hoelldobleri , while P. snellingi is well removed from the probable geographic distribution of P. hoelldobleri . Regardless, the absence of circumocular whorls separates P. hoelldobleri from both species.

Figures

FIGURE 2. Photographs of diagnostic characters to distinguish between workers of P. magnacanthus Cole and those of P. hoelldobleri Johnson, Overson & Moreau and P. m o h a v e n s i s Johnson. Photograph of P. magnacanthus PARATYPE worker: (A) eye and malar area (MOD = 0.44, OI = 29.5, MR = 0.98), and circumocular whorls indistinct to absent, moderately granulate toward vertex, and (B) circumocular whorls present. Photograph of P. hoelldobleri worker: (C) eye and malar area for HOLOTYPE worker (MOD = 0.36, OI = 23.2, MR = 1.17), and absence of circumocular whorls—rugae converging near vertex, and (D) absence of circumocular whorls—area posterior to eyes with faint rugae. Photograph of P. m o h a v e n s i s worker: (E) eye and malar area for PARATYPE worker (MOD = 0.33, OI = 21.7, MR = 1.36), and absence of circumocular whorlsrugae extending to vertex, with rugae becoming weak to absent on / near vertex, and (F) absence of circumocular whorls—rugae extending to vertex; vertex rugose.

FIGURE 3. Bivariate plots for workers: (A) maximum eye diameter versus head width, (B) ocular index versus head width, and (C) malar ratio versus head width (n = 63 for P. magnacanthus Cole, n = 59 for P. hoelldobleri Johnson, Overson & Moreau, plus 16 PARATYPE workers of P. magnacanthus that do not belong to the latter species [see text], n = 25 for P. mohavensis Johnson). Non-type workers were selected to represent the geographic range of each species.

FIGURE 6. Photograph of Pogonomyrmex hoelldobleri Johnson, Overson & Moreau—HOLOTYPE worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body.

FIGURE 7. Photograph of Pogonomyrmex hoelldobleri Johnson, Overson & Moreau alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body.

FIGURE 8. Photograph of Pogonomyrmex hoelldobleri Johnson, Overson & Moreau male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body.