Pseudomyrmex apache, Creighton, 1953

Ward, Philip S. & Branstetter, Michael G., 2022, Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:, Insect Systematics and Diversity (AIFB) 6 (1), pp. 1-31 : 18-19

Pseudomyrmex apache ; Ward 1985: 231 (part).

Pseudomyrmex psw053; Chomicki et al. 2015: 4. Placement in molecular phylogeny.

Holotype Worker. MEXICO Michoacán: 20 km S Uruapán , 880 m, 19° 14 ′ N 102° 03 ′ W, 28 Dec 1987, ex dead twig of vine, tropical dry forest, P. S. Ward PSW09293 ( UNAM) ( CASENT0863536 ) . Paratypes: series of workers, same data as holotype ( CASC, CZUG, IEXA, MCZC, PSWC, UCDC, USNM).

Other material examined ( CASC, JTLC, LACM, MCZC, PSWC, RAJC, SEMC, UCDC, USNM).

Mexico, Baja California: 19 km E El Arco, 400 m (Suarez, A. V.); 25 mi N El Arco (Ewart, W. H.); Palm Cyn., Angel de la Guardia Is. (Van Duzee, E. P.); Baja California Sur: 1 km NE La Burrera, 500 m (Ward, P. S.); 12 mi S Guillermo Prieto (Wasbauer, M.); 13 mi SW Guillermo Prieto (Phelps, B.; Phelps, M.); 19 mi SE El Cien (Andrews, F.; Faulkner, D.); 2 km WSW Todos Santos, 5 m (Ward, P. S.); 2.5 mi S Hwy.1 on rd. to Pta Agua Verde, 325 m (Johnson, R. A.); 2.7 mi SE Valle Perdido (c.u. [Snelling?]); 28–29 km N Todos Santos, 275 m (Fisher, E.; Westcott, R.); 4.8 km N San Ignacio (Savary, W. E.; Mullinex, C. L.); 59 mi SE Guerrero Negro (Andrews, F.; Faulkner, D.); 7 mi NW Santa Rosalia , 260 m (Snelling, R. R.); 72 mi NW La Paz, 30 m (Snelling, R. R.); Bahia de Los Frailes (Ira LaRivers); Las Barracas (DeBach, P.); Playa Los Cerritos (Andrews, F.; Faulkner, D.); San Domingo (Ross; Bohart); San Jose del Cabo (c.u.); Triunfo (Michelbacher; Ross); Venancio (Michelbacher; Ross); Colima: 13 mi NE Comala, El Jabali (Ballmer, G.); 16 km NNE Comala, 1,280 m (Ward, P. S.); Jalisco: 20 mi W of Tecolotlán (Lipovsky, L. J.); 39 km N Colima, 970 m (MacKay, W. P.); Est. Biología Chamela, 100 m (Ward, P. S.); Mun. Zapotiltic, 24 km S Cd. Guzman, 1,095 m (MacDougal, J.); Tecolotlan (Villegas, B.); Michoacán: 20 km S Uruapán, 880 m (Ward, P. S.); Morelos: 7.3 mi S Yautepec, 1,066 m (Carney, L. B.); Nayarit: 13.9 mi E San Blas (Janzen, D. H.); 19.3 km S Rosamorada, 30 m (MacKay, W. P.); Isla Tres Marias, Maria Madre Id.Village (Keifer, H. H.); Oaxaca: Juquila, San Juan Mixtepec, 36 km W Puerto Escondido, 23 m (Kautz, S.); Puebla: 3 km SW El Salado, 850 m (da Silva, P.G.; Eager, T.); Sinaloa: 1 km NNE Chupaderos, Hwy 40, 400 m (Ward, P. S.); 23.5 mi SW El Palmito, mi 1704.8 (Janzen, D. H.); 4.2 mi S Villa Union on Hwy. 15 (Janzen, D. H.); 5 km E Concordia , 50 m (Ward, P. S.); Sonora: Rancho El Palmarito, 23 km E Alamos, 470 m (Irwin, M. E.); La Quintera (Timberlake).

Worker measurements (n = 17). HW 0.82–0.97, HL 0.99–1.19, MFC 0.030 –0.052, LHT 0.69–0.85, CI 0.80–0.85, FCI 0.036 –0.055, REL 0.42–0.47, REL2 0.52–0.58, FI 0.42–0.46, PLI 0.49–0.57, PWI 0.45–0.55, MSC 2–5.

Worker Diagnosis. Small to medium-sized species ( HW 0.82–0.97) with moderately elongate head ( CI 0.80–0.85) and eyes (see REL and REL2 values); frontal carinae separated by less than basal scape width; metanotal groove present but weakly impressed; in profile, dorsal face of propodeum rounding obtusely into declivitous face, the two faces subequal in length; petiole relatively slender ( PLI 0.49– 0.57, PL/HL 0.50–0.56), in profile the convex anterodorsal face of petiole ascending gradually to summit in the posterior half of node, then rounding into more rapidly descending posterior face (Fig. 5); profemur slender; hind leg relatively short ( LHT /HL 0.68–0.72). Head sublucid, densely punctulate-coriarious to coriarious-imbricate. Standing pilosity sparse, absent from propodeum and mesonotum ( MSC 2–5). Uniformly light yellow-brown to orange-brown.

Comments. This species is characterized by a combination of light yellow-orange coloration, without additional maculation; moderately elongate eyes; weakly impressed metanotal groove (in the worker); and slender petiole. The workers of P. arcanus can be distinguished from those of other orange-yellow species in the P. elongatulus group as follows. Pseudomyrmex elongatulus has a better-developed metanotal groove, more elongate eyes ( REL 0.47–0.53), petiole ( PL /HL 0.57–0.61) and legs ( LHT /HL 0.74– 0.79), and some degree of infuscation on the gaster. Pseudomyrmex exoratus has a much more elongate head ( CI 0.67–0.69) and a robust profemur ( FI 0.46–0.49). Pseudomyrmex fasciatus essentially lacks a metanotal groove (as seen in in profile) and has conspicuous transverse maculation on the gaster. Pseudomyrmex apache has shorter eyes (on average), a more angular propodeum, and a more robust petiole, and the tip of the gaster is frequently darkened. Although they are not one another’s closest relatives (Fig. 1), P. apache and P. arcanus can be difficult to distinguish, the differences in propodeal and petiole shape being rather subtle. Bivariate plots of some measurements reveal two separate clouds of points ( Fig. 3 ), but increased samples sizes might show some overlap.

In our UCE phylogeny there is an early diverging sample of P. arcanus (D1228) that is sister to all others (Fig. 1; Supp Fig. 4 [online only]). This is a southern outlier, from Oaxaca (Supp Table 2 [online only]), but we do not treat this as a separate species because 1) it is phenotypically similar to other samples of P. arcanus , 2) it is allopatric to the other populations, and 3) there are geographically intermediate populations from southern Mexico ( Fig. 20 ) which we did not have an opportunity to sequence. More intensive sampling of such southern populations could be expected to reveal a paraphyletic series at the base of the P. arcanus tree, for which excisement of D1228 would be arbitrary and ill-founded.

Distribution and Biology. This species is found at low to medium elevations in western Mexico, from Baja California to Oaxaca. Recorded elevations vary from 5 m to 1,280 m (mean 474 m; n = 19). Habitats in which P. arcanus has been collected include coastal sand dunes, pasture, tropical dry forest, and mixed tropical/ temperate mesic forest. Nests have been taken in a dead stalk of a woody Asteraceae (? Viguiera ), dead stem of Cassia , dead twig of thorny vine, dead twig of vine, and dead twigs of unidentified woody plants. The records of ‘ Pseudomyrmex apache ’ cited in Ward (1985: 231) from Baja California refer to this species.

Figures

Fig. 3. Bivariate plots of measurements and indices concerned with eye size and petiole shape, in workers of P. apache (n = 17) and P. arcanus (n = 17). (a) PL/ LHT (petiole length/metatibia length) by HW (head width); (b) REL2 (eye length/head width) by PLI (petiole height/petiole length).

Fig. 19–26. Pseudomyrmex elongatulus group: distribution maps. 19, P. apache; 20, P. arcanus (circles), P. fasciatus (triangles); 21, P. championi; 22, P. capillatus (triangles), P. cognatus (circles); 23, P. elongatulus (circles), probable introduced populations (stars); 24, P. comitator (square), P. ereptor (triangle), P. exoratus (circles); 25, P.salvini; 26, P. nimbus (circles), P. veracruzensis (triangle).