Temnothorax tuxtlanus, Prebus, 2021

Prebus, Matthew M., 2021, Taxonomic revision of the Temnothorax salvini clade (Hymenoptera: Formicidae), with a key to the clades of New World Temnothorax, PeerJ (e 11514) 9, pp. 1-462 : 81-85

Temnothorax tuxtlanus sp. nov.

Distribution: Fig. 90B ; worker: Fig. 92 .

Type material examined: Holotype worker: MEXICO: Veracruz: Ruiz Cortinez, 12 km NE San Andrés Tuxtla , 18.53194 ° N -95.14302 ° W ± 20 m, 1,140 m, 3 June 2016, ADMAC#Wa-F-02-2-31 , montane wet forest, ex sifted leaf litter ( CASENT0640472 ) [ CASC].

Geographic range: Southern Mexico, mid elevation of the Los Tuxtlas volcano complex ( Fig. 90B ).

Worker diagnosis: Temnothorax tuxtlanus sp. nov. can be separated from all other members of the salvini clade by the following character combination: dorsum of mesosoma weakly sinuate in profile view; dorsum of propodeum without erect setae; petiole with a weak transverse carina anterodorsally; petiolar peduncle short, comprising about a quarter of the total petiole length; petiolar node rounded dorsally; postpetiole relatively narrow (PWI <170); setae on head, mesosoma, waist segments and gaster erect, short, sparse and blunt (never long and tapering); integument black, with antennae, mandibles, pronotal neck, coxae, and femora dark brown; trochanters, tibiae, and tarsi testaceous yellow.

Similar species: Temnothorax achii sp. nov.,, T. acuminatus sp. nov., T. acutispinosus sp. nov., T. altinodus sp. nov., T. ixili , T. subditivus , T. xincai sp. nov., members of the augusti and pulchellus groups, and species of the sallei clade. Temnothorax tuxtlanus sp. nov. can be distinguished from similar appearing members of the sallei clade (e.g. T. manni , T. mexicanus , T. punctithorax ) by the sculpture of the head: in similar looking sallei clade species, the head is mostly smooth and shining, with concentric costulae surrounding the antennal insertions; additionally, the medial lobe of the clypeus is typically smooth, with three distinct carinae, whereas it is densely costulate-rugulose in T. tuxtlanus sp. nov. In contrast to all of the remaining species above, the petiole of T. tuxtlanus sp. nov. has a weak transverse carina anterodorsally, a feature not found in other members of the salvini clade, except for T. acuminatus sp. nov., T. altinodus sp. nov., T. rugosus , and the annexus group. Temnothorax tuxtlanus sp. nov. is easily separated from all of the preceding species, except T. acuminatus sp. nov., by the weakly incrassate hind femora (FI <300) and lack of a medial notch in the anterior margin of the clypeus. Temnothorax tuxtlanus sp. nov. can be distinguished from T. acuminatus sp. nov. by the dorsally rounded petiolar node, which is cuneiform in T. acuminatus sp. nov. Finally, this species may be distinguished from the morphologically similar T. acutispinosus sp. nov. by the smaller subpetiolar tooth and more posteriorly directed propodeal spines.

Worker measurements & indices (n = 1): SL = 0.524; FRS = 0.222; CW = 0.671; CWb = 0.630; PoOC = 0.316; CL = 0.720; EL = 0.178; EW = 0.116; MD = 0.142; WL = 0.869; SPST = 0.185; MPST = 0.268; PEL = 0.329; NOL = 0.190; NOH = 0.118; PEH = 0.224; PPL = 0.229; PW = 0.423; SBPA = 0.199; SPTI = 0.204; PEW = 0.165; PNW = 0.128; PPW = 0.239; HFL = 0.551; HFWmax = 0.132; HFWmin = 0.047; CS = 0.990; ES = 0.236; SI = 83; OI = 24; CI = 88; WLI = 138; SBI = 32; PSI = 21; PWI = 145; PLI = 144; NI = 161; PNWI = 78; NLI = 58; FI = 281.

Worker description: In full-face view, head subquadrate, longer than broad (CI 88). Posterior head margin flat, rounding evenly into the lateral margins. Mandibles weakly, finely striate but shining and armed with five teeth: the apical-most well developed and acute, followed by a less developed preapical tooth and three equally developed smaller teeth. Anterior clypeal margin very weakly convex medially. Antennal scapes short: when fully retracted, failing to reach the posterior margin of the head capsule by about the maximum width of the scape (SI 83). Antennae 12-segmented; antennal club of composed of three segments, with the apical-most segment slightly longer than the preceding two in combination. Frontal carinae short, extending past the antennal toruli by about two times the maximum width of the antennal scape. Compound eyes weakly protruding past the lateral margins of the head capsule. Lateral margin of head weakly convex, forming a continuous arc from the mandibular insertions to the posterior margin of the head. Posterior head margin flat, rounding evenly into the lateral margins.

In profile view, compound eyes elongate-ovular and moderately large (OI 24), with 12 ommatidia in longest row. Pronotal declivity indistinct, neck and anterior face of pronotum forming a ~120 ° angle. Mesosoma weakly sinuate: evenly convex from where it joins the pronotal neck to the metanotal groove; propodeum slightly depressed below the level of the promesonotum, and flat. Promesonotal suture extending from the posterior margin of the procoxal insertion to the mesothoracic spiracle, which is moderately well developed, then continuing dorsally as a very weak sulcus. Metanotal groove visible as a disruption of the sculpture laterally from where it arises between the mid- and hind coxae to the poorly developed metathoracic spiracle, which is nearly indistinguishable against the ground sculpture, then continuing dorsally as a moderately strong impression. Propodeal spiracle weakly developed, directed posterolaterally, and separated from the propodeal declivity by about three spiracle diameters. Propodeal spines short (PSI 21), about half the length of the propodeal declivity, tapering evenly from the base, straight, and acute. Propodeal declivity weakly concave, forming a rounded ~110 ° angle with the base of the propodeal spines. Propodeal lobes rounded and weakly developed, but dorsal margin weakly angulate. Metapleural gland bulla moderately large, extending from the metacoxal insertion two thirds of the way to the propodeal spiracle. Petiole short (PLI 144), with tubercles anterodorsally. Subpetiolar process in the form of a tiny, blunt, triangular tooth which grades evenly into the ventral margin of the petiole posteriorly; ventral margin of petiole flat posterior to it. Petiolar peduncle short: comprising about a quarter of the total petiole length. Petiolar node erect and dorsally rounded: peduncle grading evenly into the anterior node face; anterior face forming a ~100 ° angle with the evenly rounded dorsal face; dorsal face rounding evenly into the posterior face; posterior face forms a ~110 ° angle with the caudal cylinder. Postpetiole evenly rounded anteriorly; dorsal face flat; weakly lobed ventrally, subpostpetiolar process acute.

In dorsal view, humeri developed and distinct: evenly rounded and wider than the rest of the mesosoma; mesothoracic spiracles weakly protruding past the lateral margins of the mesosoma, visible as slight angles where the pronotum meets the mesonotum. Promesonotal groove visible as a weak sulcus and disruption in the ground sculpture. Metanotal groove visible as a distinct sulcus. Propodeal spines broadly approximated basally and weakly diverging apically, their apices separated from each other by about one and a half times their length, the negative space between them “U” shaped. Petiolar peduncle with spiracles weakly protruding past the lateral margins, and slightly constricted anterior to them. Petiolar node, when viewed dorsally, quadrate. Apex of node slightly narrower than the peduncle and caudal cylinder. Postpetiole narrow (PWI 145) and longitudinally elongate. Anterior margin of the postpetiole convex and evenly rounds into the lateral margins; lateral margins parallel to each other; posterior margin flat. Metafemur moderately incrassate (FI 281).

Sculpture: six equally strong clypeal carina present, extending posteriorly to the frontal triangle; clypeus appearing costulate-rugulose. Lateral clypeal lobes with additional, weaker carinae; ground sculpture weakly areolate. Antennal scapes weakly areolate. Cephalic dorsum predominantly areolate, with the areolae arranged into longitudinal rows by fine costulae; very fine concentric costulae surrounding the antennal insertions. Lateral surfaces of head sculptured similarly to the dorsum, but with areolae arranged into concentric whorls by fine costulae above the compound eyes; fine rugulose sculpture overlying the areolae between the compound eye and mandibular insertion. Ventral surface of head smooth and shining, with weak costulae. Pronotal neck areolate. Anterior face of the pronotum weakly areolate-strigulate. Lateral surface of mesosoma predominantly weakly areolate, with fine costulae overlying the ground sculpture. Propodeal declivity areolate, with fine strigulae overlying the ground sculpture. Dorsal surface of mesosoma uniformly areolate; fine strigulae on the anterior margin of the pronotum; fine costulae on the mesonotum; fine areolate-rugulose sculpture on the dorsal face of the propodeum. Femora shining, with weak areolate sculpture on the distal third. Petiole and postpetiole predominantly weakly, areolate-rugulose. First gastral tergite finely, weakly areolate-rugulose on the basal half, otherwise smooth and shining, without spectral iridescence. First gastral sternite densely areolate, without spectral iridescence.

Setae: antennal scapes and funiculi with short, decumbent pilosity. Dorsum of the head, pronotum, waist segments, and gaster with moderately abundant, erect, blunt-tipped setae, the longest of which are about half the width of the compound eye. The head bears ~30, mesosoma ~10, petiole 4, postpetiole ~12, and first gastral tergite ~68 setae. Short, sparse pubescence present over the entire body, but difficult to detect against the densely sculptured integument.

Color: predominantly black, with antennae, mandibles, pronotal neck, coxae, and femora dark brown. Trochanters, tibiae, and tarsi testaceous yellow.

Gyne: Unknown.

Male: Unknown.

Etymology: Geographical, from Los Tuxtlas, an isolated volcanic mountain range near the Gulf of Mexico in Veracruz state, Mexico where the holotype worker was collected.

Comments: Temnothorax tuxtlanus sp. nov. is known only from the holotype worker, collected via Winkler leaf litter extraction in mid elevation montane wet forest. The closest known relative of T. tuxtlanus sp. nov. is T. acuminatus sp. nov. from the Sierra Madre de Chiapas in Chiapas state. Together, T. tuxtlanus sp. nov. and T. acuminatus sp. nov. form the acuminatus species group, which is sister to the remainder of the salvini clade.

Figures

Figure 90 Geographical and elevational distribution of the acuminatus group. (A) Temnothorax acuminatus sp. nov. (B) T. tuxtlanus sp. nov. Colored scale to the left of each map represents elevation in meters. Points in black represent the species named in each subfigure, while points in red represent other members of the species group. Type localities are represented by triangles, non-type localities are represented by circles. Bounding box in inset map shows location of main map. Full-size DOI: 10.7717/peerj.11514/fig-90

Figure 92 Temnothorax tuxtlanus sp. nov. holotype worker (CASENT0640472). (A) Profile view. (B) Full-face view. (C) Dorsal view. Scale bars 0.2 mm. Full-size DOI: 10.7717/peerj.11514/fig-92