Sericomyrmex maravalhas, Jesovnik, Ana & Schultz, Ted R., 2017

Jesovnik, Ana & Schultz, Ted R., 2017, Revision of the fungus-farming ant genus Sericomyrmex Mayr (Hymenoptera, Formicidae, Myrmicinae), ZooKeys 670, pp. 1-109 : 48-54

Sericomyrmex maravalhas sp. n. Figures 32, 33(Worker); Figure 34(Queen); Figure 35 (Map)

Type material.

Holotype worker: BRAZIL, Mato Grosso, Serra Azul State Park, Barra do Garças, -15.8571, -52.2617, 539m, 5 Jun 2011, H. Vasconcelos (MZSP: 1w, USNMENT00924081). Paratypes: same data as holotype (MZSP: 1w, USNMENT00924090) (USNM: 1q, USNMENT00924082; 1w, USNMENT00924087; 1w, USNMENT00924089), (MBC-UFU: 1w, USNMENT00924083), (MCZ: 1w, USNMENT00924092), (CASC: 1w, USNMENT00924086; 1w, USNMENT00924091), (BMNH: 1w, USNMENT00924088), (MHNG: 1w, USNMENT00924095).

S. maravalhas worker diagnosis.

Small species; frontal lobe triangular; frontal carina robust, complete; eye convex, sometimes laterally protruding in full-face view; mandible dorsally glossy, smooth; gaster with four sharp carinae.

S. maravalhas worker description.

Measurements in mm, range (holotype): HWe 0.80-0.98 (0.95) HW 0.78-1.00 (0.96) HW1 0.75-1.2 (0.98) HW2 0.82-1.08 (1.03) HW3 0.54-0.75 (0.63) IFW1 0.51-0.68 (0.64) IFW2 0.19-0.30 (0.2) HL1 0.77-0.95 (0.88) HL2 0.68-0.83 (0.8) SL 0.58-0.73 (0.68) EL 0.13-0.2 (0.18) Om 8-11 (9) WL 1.03-1.28 (1.2) PL 0.21-0.32 (0.23) PPL 0.13-0.25 (0.21) GL 0.72-0.95 (0.85) HFL 0.82-1.08 (1) PW 0.52-0.71 (0.66) CI 97-110 (108) FLI 57-73 (67) SI 67-77 (72) OI 15-21 (19) CEI 7-17 (8) [N=30]

Pilosity. Pubescence dense, lighter than integument, appressed to decumbent. Hairs curved, darker in color at base, appressed to suberect, mostly decumbent.

Head. In full-face view slightly broader than long (CI=104 ± 3), posterior corner angular to acute, lateral margin of head slightly convex, posterior cephalic emargination distinct (CEI=10 ± 2), gradually impressed. Vertexal impression distinct, frontal tumuli faint. Mandibles with 7-8 teeth, dorsally smooth and shiny, finely transversely striate only along masticatory margin. Eye large (OI =18 ± 1), moderately convex, without white layer, 9-11 ommatidia across largest diameter. Frontal lobe relatively wide (FLI=68 ± 2), triangular, posterior margin shorter than medial, lateral margin in some specimens mildly concave. Frontal carina well developed, complete, reaching posterior cephalic corner. Antennal scape moderately long, sometimes almost reaching posterior cephalic corner (SI=72 ± 3).

Mesosoma. Mesosomal tubercles low and obtuse to moderately pronounced. Propodeal carinae low, sometimes serrate, sometimes with posterodorsal denticles.

Metasoma. Petiole and postpetiole each with two low, short, serrate carinae dorsally, on petiole sometimes reduced to denticles, best seen in dorsolateral view. Postpetiole usually with another pair of low carinae laterally. First gastral tergite with lateral and dorsal carinae strongly developed (Figure 32c, 33f).

S. maravalhas queen description.

Measurements in mm: HWe 1.12 HW 1.12 HW1 1.24 HW2 1.36 HW3 0.84 IFW1 0.84 IFW2 0.4 HL1 1.12 HL2 0.99 SL 0.75 EL 0.24 Om 20 EW 0.08 WL 1.72 PL 0.33 PPL 0.3 GL 1.6 HFL 1.25 PW 1 CI 100 FLI 75 SI 67 OI 22 [N=1]

Head. Mandible with 8 teeth, dorsally glossy and smooth, finely transversely striate only along masticatory margin. Preocular carina extending posterior to eye, becoming thinner posteriorly, almost converging with frontal carina to form complete scrobe, best seen in lateral view. Eye large, convex, protruding from sides of head in full-face view, 20 ommatidia across largest diameter. Frontal lobe as in worker, antennal scape not reaching posterior cephalic corner (SI=67).

Mesosoma. Lateral pronotal tubercles low and obtuse. Scutum in dorsal view with notauli and median mesoscutal line faint. Parapsidal lines thin, slightly curved. Groove separating axillae in dorsal view weakly transversely costate. Scutellum inflated, short in dorsal view, narrowing posteriorly, with relatively deep V-shaped posterior notch. Propodeum with two obtuse, laterally flattened, diverging denticles.

Metasoma. First gastral tergite with lateral carinae strongly developed, dorsal carinae faint, anteromedian groove distinct.

S. maravalhas male.

Unknown.

S. maravalhas geographic range.

Interior of Brazil, cerrado habitats. Map: Figure 35.

S. maravalhas notes.

S. maravalhas can be separated from its sister species S. scrobifer by its smaller size; narrower, triangular frontal lobes (trapeziform in scrobifer ); less robust frontal carinae; and eyes somewhat smaller and flatter (Figure 5d). The closely related S. saramama is similar in size but differs from maravalhas by the absence of dorsal gastral carinae, less robust frontal lobes and frontal carinae, and smaller, flatter eyes. S. opacus , which is similar in size and has smooth mandibles, can be distinguished from maravalhas by the absence of dorsal gastral carinae; smaller, flat eyes, sometimes with a white layer; weaker, incomplete frontal carinae; and opacus -typical rectangular frontal lobes.

In addition to characters that are the same as in the worker, the most diagnostic character of the S. maravalhas queen is the presence of fully developed preocular carinae that almost join with the frontal carinae posteriorly, a relatively deep notch in the posterior margin of the scutellum, and large propodeal denticles. However, because our description is based on a single specimen, we do not know if these characters vary within the species.

Sister species S. maravalhas and S. scrobifer have consistent morphological and molecular differences and their distributions overlap, possibly substantially, which reinforces our decision to recognize them as distinct species. However, distributional data for both species are clearly incomplete (Figure 35) and it remains entirely possible that, due to undersampling, we may be unaware of forms that are morphologically and/or molecularly intermediate between the two species, which, if they exist, might compel us to reevaluate them to be a single species. Currently, however, based on all of the material examined, the results of the morphological measurement analyses (Figure 3FLI, Figure 5d), and the branch lengths separating the two species in the molecular phylogeny (Suppl. material 1), we have chosen to recognize maravalhas as distinct from scrobifer .

An interesting feature of S. maravalhas is that, unlike adult workers of all other Sericomyrmex species that we examined under SEM, some of the maravalhas workers lack the thick, waxy, crystal-like cuticular layer (Figure 33h). In S. maravalhas this layer can be entirely (Figure 33g) or partially (Figure 33e, i) absent so that the minutely papillate integument is visible (Figure 33g), a condition otherwise known only in males and callow workers of other Sericomyrmex species (Figure 6 d–e). We know nothing about the chemical composition or function of this white, crystal-like layer, but the two most likely explanations are that it is either a cuticular secretion or microbial in origin. Considering the known complex microbial interactions in the attine ant symbiosis ( Currie et al. 2003, 2006, Fernández-Marín et al. 2006, Little and Currie 2007), and considering that this layer covers the eyes of some Sericomyrmex species (see S. saussurei notes for discussion), this phenomenon needs to be further investigated.

S. maravalhas etymology.

This species is named after our myrmecologist colleague Jonas Maravalhas, who sorted and sent to us the specimens of this species used in our molecular phylogenetic analyses. The molecular data were crucial, in combination with morphological evidence, for recognizing maravalhas as a distinct species. Even better, Jonas’ surname has the same root as “maravilhas” which means “wonders” in Portuguese, an appropriate adjective for this new species. The species name is a noun in apposition.

Material examined.

BRAZIL: Mato Grosso: Coxim, Rio Taquari, [-18.5264, -54.7465], 1 Dec 1963, V. C. Andzada; Near Poconé, Transpantaneira Km115, [-16.2597, -56.6269], 28 Nov 1984, J. C. Trager; Serra Azul State Park, Barra do Garças, -15.8571, -52.2617, 539m, 5 Jun 2011, H. Vasconcelos; Mato Grosso do Sul: Campo Grande, -20.4261, -54.7275, 532m, 7 Oct 2012; Tocantins: Araguacema, Rio Tiririca, -8.9886, -49.6675, 16 Nov 2005, R. R. Silva, R. M. Feitosa; Ponte Alta do Bom Jesus, -12.1212, -46.6176, 7 Oct 2004, R. R. Silva, B. H. Dietz.