Protanilla wallacei, Griebenow, 2024

Griebenow, Zachary, 2024, Systematic revision of the ant subfamily Leptanillinae (Hymenoptera, Formicidae), ZooKeys 1189, pp. 83-184 : 83

Protanilla wallacei sp. nov.

Fig. 4A-C

Type material.

Holotype. Malaysia - Sarawak • 1 worker; Gunung Mulu National Park, 4th division; 4.09°N, 114.89°E (estimated from Google Earth to nearest minute); May-Aug. 1978, P. M. Hammond and J. E. Marshall leg.; CASENT0902782; BM1978-49, BMNH(E) 1015826. BMNH. Paratype. Malaysia - Sabah • 1 worker; Gunung Silam, Lahad Datu; 4.96°N, 118.17°E (estimated from Google Earth to nearest minute); 630m a.s.l.; 1983; R. Leakey leg; CASENT0842699; UCDC.

Other material examined.

Malaysia - Sabah • 1 worker; 8km S Sapulut , 4.62844°N, 116.47175°E; 325m a.s.l.; 31.vii.2014; P. S. Ward leg.; sifted litter (leaf mold, rotten wood), rainforest; CASENT0842640; PSW17199-01. UCDC .

Measurements (mm) and indices.

Holotype: N/A Paratype: HL = 0.42; HW = 0.33; SL = 0.22; PW = 0.27; WL = 0.68; PTL = 0.2; PTW = 0.19; PPTL = 0.19; PPTW = 0.2; CI = 79; SI = 106; PI = 98; PPI = 113. Other material examined (n = 2): HL = 0.43-0.46; HW = 0.35-0.36; SL = 0.33-0.39; ML = 0.21-0.24; PW = 0.26-0.29; WL = 0.64-0.72; PTL = 0.19-0.21; PTW = 0.2; PPTL = 0.19-0.21; PPTW = 0.2-0.23; CI = 78-80; SI = 97-102; PI = 93-101; PPI = 105-108

Description.

Lateral cranial margins converging anteriorly; cranium not bulging towards vertex. Genal angle laterad antennal toruli obtuse. Outline of clypeus campaniform in full-face view, laterally elevated above cranium, posteriorly not elevated above frons; clypeal surface planar; anterior clypeal margin slightly emarginate, posteromedian clypeal margin emarginate; median clypeal ridge present on mesal surface of clypeus, externally visible. Labrum visible in full-face view; anterodorsal apex of labrum armed with three or four dentiform, peg-like chaetae; venter with vestiture of suberect lanose setae. Mandibles elongate relative to head (CI = 79-80), linear, apex curved downward distally; vertical dorsal lamella absent; laterodorsal longitudinal groove present; dorsomedial margin of mandible with single row of ~ 12 dentiform, peg-like chaetae; lateral mandibular face glabrous. Labial palp 1-merous. Anterior tentorial pits faint, situated anterad the toruli, not visible in full-face view. Postgenal ridge complete. Scape long (SL 0.34-0.39 mm), reaching slightly beyond occipital margin when antennae retracted. Flagellum submoniliform; apical flagellomere 3 × longer than broad. Pronotum broader than mesonotum in dorsal view, with lateral margins convex. Mesonotum narrow, with lateral margins parallel in dorsal view. Meso-metapleural suture narrow laterally, broader along dorsal surface; scrobiculate, with transverse ridges larger and more widely spaced along dorsal surface of meso-metapleural suture; posteriorly distinct from metapleural trench. Maximum breadth of metapectal-propodeal complex greater than that of mesonotum in dorsal view, slightly narrowed anteriorly, posterior outline convex in profile view. Bulla large, extending anterior to propodeal spiracle. Propodeum rounded in profile view. Tarsomeres longer than broad. Meso- and metatibial spur formula 0,1p. Petiole sessile. Abdominal segments II and III without tergotergal and sternosternal fusion. Abdominal segment II slightly longer than wide in dorsal view (PI 94-99), with distinct dorsal node, in profile view anterior and posterior faces subequal in height; anterior face of petiolar node linear in profile view. Subpetiolar process present, abdominal sternite II with concavity posterior to subpetiolar process so that margin of abdominal sternite II is sinuate in profile view; fenestra present, elliptical, anteroposteriorly compressed. Lengths of abdominal segments II-III subequal. Abdominal sternite II projecting no further than abdominal sternite III towards venter. Abdominal segment III slightly broader than long in dorsal view (PPI = 105-113), with distinct dorsal node; in profile view, anterior face of dorsal node abruptly vertical and bulging, posterior face gently sloping. Post-petiole with distinct tergosternal suture. Abdominal segments III-IV separated by pronounced constriction, with presclerites of abdominal segment IV distinct; pretergite IV planar in profile view, shorter than presternite IV; presternite IV slightly convex in profile view; cinctus of abdominal segment IV scrobiculate. Anterior margin of abdominal post-tergite IV shallowly emarginate in dorsal view. Outline of postpetiolar node trapezoidal in dorsal view, corners rounded, slightly narrowed anteriorly. Soma concolorous, color castaneous. Vestiture of suberect to erect setae present; length of setae variable.

Etymology.

Named for Alfred Russel Wallace, commonly thought to be the progenitor of the discipline of biogeography and still well-regarded for his study of the biota of the Malay Archipelago, where this ant is native. The specific epithet is masculine, in genitive case.

Remarks.

The worker caste of P. wallacei is extremely close to that of P. lini but differs in overall smaller size and the shallowness of the postpetiolar node, with the posterior declivity of the postpetiolar node being gradual (Fig. 5B ) rather than abrupt (Fig. 5A ). PPI tends to be greater in P. wallacei (x_ = 109) than in P. lini (x_ = 100) but cannot be consistently used to discriminate the two. Interestingly, all known gynes of P. wallacei are ergatoid ( Billen et al. 2013; Ito et al. 2022), whereas those of P. lini are alate ( Hsu et al. 2017).

Protanilla wallacei appeared as a nomen nudum in Hölldobler and Wilson (1990), with the name purportedly being under description by Robert W. Taylor based upon material from Sabah. Such a description has not appeared. CASENT0842699 was identified as P. wallacei by Barry Bolton with reference to “type” material under description by Taylor, which, based on a paratype label assigned by Taylor, included CASENT0902782. Billen et al. (2013) described the glandular complement of specimens from peninsular Malaysia that was attributed to this nomen nudum by Taylor, while Ito et al. (2022) reported on the behavioral observations of specimens from that same series, referring to this species as Protanilla sp. Protanilla wallacei is here made an available name, described based upon worker specimens from Sabah. Judging from Billen et al. (2013: fig. 5E), the series referred to in that study and in Ito et al. (2022) conforms to the diagnosis of P. wallacei here given. The unidentified Protanilla that was the sole representative of the Leptanillinae in the phylogenomic analyses of Branstetter et al. (2017) (CASENT0634862) is here identified as P. wallacei . Protanilla wallacei shows intraspecific variation in labral chaeta count, which is also observed in putatively conspecific allopatric specimens of P. gengma ( Aswaj et al. 2020; pers. obs.) and P. beijingensis (this study).

Protanilla wallacei and P. lini are recovered as sister taxa in phylogenomic inference sampling from across the geographical range of the latter species (pers. obs.). Protanilla lini ranges across Taiwan and the Ryukyu Islands, while the P. wallacei specimens examined in this study originate in the Sundan region. This allows for the possibility that these putative species are populations from extreme ends of a contiguous swath of metapopulations extending throughout southeast Asia. Further sampling in mainland southeast Asia may reciprocally efface the morphometric distinction between these species, and with the other members of the Protanilla lini species complex.

Figures

Figure 4. Protanilla wallacei, holotype (CASENT 0902782; Ziv Lieberman), worker A profile view B dorsal view C full-face view. Scale bars: 0.2 mm (A, B); 0.1 mm (C).

Figure 5. Worker petiole of Protanilla lini (a) and Protanilla wallacei sp. nov. (b), profile view. Abbreviation: dpn = petiolar node.