Discothyrea athene Hita Garcia & Lieberman, 2019

Hita-Garcia, Francisco, Lieberman, Ziv, Audisio, Tracy L., Liu, Cong & Economo, Evan P., 2019, Revision of the Highly Specialized Ant Genus Discothyrea (Hymenoptera: Formicidae) in the Afrotropics with X-Ray Microtomography and 3 D Cybertaxonomy, Insect Systematics and Diversity 5, pp. 1-84 : 31-34

Discothyrea athene Hita Garcia & Lieberman sp. n.

( Figs. 4D , 6D , 7D , 8D , 9D , 10D , 11D , 12D , 14D , 25 , 26 ; Supp Video S4 [online only])

Type Material

HOLOTYPE, pinned worker, UGANDA, Kibale National Park, Kanyawara Biological Station , 0.56437, 30.3605, 1510 m, rainforest, leaf litter, collection code FHG01060, 6.–16.VIII.2012 (F.Hita Garcia) ( BMNH: CASENT0764088 ) . PARATYPES, four pinned workers with same data as holotype ( CASC: CASENT0764102 ; MHNG: CASENT0764100 ; SAMC: CASENT0764101 ; ZMFK: CASENT0764087 ) .

Cybertype. Volumetric raw data (in DICOM format), 3D rotation video, still images of surface volume rendering, and 3D surface (in PLY format) of the physical holotype (CASENT0764088) in addition to stacked digital color images illustrating head in full-face view, profile and dorsal views of the body.The data are deposited at Dryad (Hita Garcia et al. 2019, http://doi.org/10.5061/dryad.3qm4183) and can be freely accessed as virtual representation of the type. In addition to the cybertype data at Dryad, we also provide a freely accessible 3D surface model of the holotype at Sketchfab (Model 4).

Non-type material

KENYA: Coast Province , Arabuko Sokoke Forest, −3.314367, 39.940731, 136 m, mixed forest, pitfall trap, VI.2009 (G. Fischer,

F. Hita Garcia); Coast Province, Arabuko Sokoke Forest, −3.321139, 39.929194, ca. 50 m, mixed forest, hand collected, VI.2009 (F. Hita Garcia, G. Fischer); MOZAMBIQUE: Sofala, Gorongosa, Gorongosa National Park, Camp #3, −19.032989, 34.671758, 115 m, riparian forest along creek, darker and closed, atop creek bed, Winkler, 3.V.2013 (L. E. Alonso); RWANDA : Rangiro, [-2.39361, 29.18278], 1800 m, 10.VII.1973 (P. Werner); Rangiro , [-2.39361, 29.18278], ca. 1800 m, litter, IX.1976 (P.Werner); TANZANIA : Kilimanjaro Region, Gonja Forest Reserve , −4.283333, 38.03333, 550 m, lowland forest, leaf litter, Winkler, 16.V.1996 (H.G. Robertson) ; Kilimanjaro Region, Mkomazi Game Reserve, valley behind Ibaya, −3.966667, 37.80, 900 m, closed woodland next to stream in steep-sided valley, leaf litter, Winkler , 2.XII.1995 (H.G. Robertson) ; Kilimanjaro Region, Mkomazi Game Reserve, at foot of Maji Kununua , −3.883333, 37.816667, 1600 m, Combretum thicket at base of valley, leaf litter, Winkler, 12.V.1996 (H.G. Robertson) ; Lindi Region, Rondo Forest Reserve , −10.11569, 39.18858, 870 m, primary forest, leaf litter, Winkler, 20.–23.II.2008 (P. Hawkes, Y. Mlacha, F. Ninga) ; Morogoro Region, Kanga Forest Reserve , −5.94905, 37.68539, 820 m, primary forest, leaf litter, Winkler, 23.–26.VIII.2005 (P. Hawkes, J. Makwati, R. Mtana) ; Morogoro Region, Mkungwe Forest Reserve , −6.89388, 37.90414, 700 m, primary forest, leaf litter, Winkler, 12.– 15.X.2007 (P. Hawkes, M. Bhoke, U. Richard) ; Morogoro Region, Sali Forest Reserve , −8.94497, 36.6726, 1150 m, primary forest, leaf litter, Winkler, 17.–20.X.2007 (P. Hawkes, M. Bhoke, U. Richard) ; Tanga Region, Kilindi Forest Reserve , −5.57934, 37.57971, 1015 m, primary forest, leaf litter, Winkler, F 21, 27.–30.VIII.2005 (P. Hawkes, J. Makwati, R. Mtana); UGANDA : Bundibugyo, Rwankasenyi, Semliki National Park , 0.85617, 30.16583, 690 m, swamp forest, leaf litter, 17.VIII.2012 (J. Longino) .

Diagnosis

The following character combination distinguishes Discothyrea athene from the remainder of the complex: standing pilosity absent from mesosoma and abdominal terga; propodeum denticulate; eyes present, relatively large (OI 5–9); in dorsal view mesosoma relatively broad and robust (DMI 59–67, DMI2 92–100); mesotibia without apicoventral spur; petiole attenuated dorsally (DPeI 300–500, LPeI 286–500); sculpture distinct, declivitous face of propodeum foveolate; generally smaller species (WL 0.30–0.53); color usually orange, variably infuscated.

Worker Measurements and Indices (n = 17)

EL 0.03–0.04; HL 0.39–0.49; HW 0.33–0.42; SL 0.19–0.26; PH 0.19–0.27; PW 0.23–0.32; PrH 0.23–0.30; DML 0.23–0.34; WL 0.38–0.53; HFL 0.21–0.30; PeL 0.04–0.07; PeW 0.15–0.21; PeH 0.15–0.20; LT3 0.27–0.39; LT40.25–0.33; OI 5–9; CI 80–89; SI 48–53; LMI 47–51; DMI 59–67; DMI2 92–100; ASI 85–103; HFI 53–60; DPeI 300–500; LPeI 286–500.

Worker Description

Head fairly broad (CI 80–89) and round, posterior head margin gently convex; posterodorsal corners of head broadly rounded; in frontal view, sides of head convex and tapering somewhat anteriorly; eyes present, relatively large (OI 5–9) and round, comprising several ommatidia, placed about a third of the way between anterolateral corner of gena and posterior head margin; eyes visible in frontal view; frontal lamella broadly triangular in profile, apex rounded; lamella with translucent basal region, variably developed, from an indistinct patch to an elliptical and well-defined fenestra; medial clypeus convex, lateral clypeus curving gently between antennal sockets and anterolateral corners of head, bearing short, curved setae. Antenna with short scape (SI 48–53), scape strongly incrassate, slightly bent; pedicel subglobose, broader than long; true antennomere count nine; apparent antennomere count seven to nine; flagellomeres basad apical club highly compressed, taken together only about as long as apical club. Ventral head with postoccipital ridge weakly developed, without anteromedian carina; hypostoma medially rounded, arms somewhat narrowed, similar in width across their length; palpal formula not examined. Mandible edentate except for small, sharp prebasal denticle; basal angle broadly rounded; longitudinal carina on ectal face confluent with masticatory margin for most of its length, leaving small depressed triangular area anterad prebasal denticle.

Mesosoma gently convex, pronotum slightly lower than propodeum. In dorsal view mesosoma broad, robust (DMI 59–67; DMI2 92–100), somewhat narrowed posteriorly, pronotum wider than propodeum; pronotal humeri moderately rounded; posterior propodeal margin concave, distinctly concave between dentae; posterodorsal corners of propodeum angulate to dentate, teeth blunt but distinct; declivitous face of propodeum distinctly concave in profile and oblique posterior view; propodeal spiracle relatively large, subcircular, directed posterolaterally, often conspicuous due to shiny, unsculptured spiracular opening; propodeal lobes short, rounded.

Legs short to moderate in length (HFI 53–60) and slender; mesotibia without apicoventral spur, with small but distinct Model 4. 3D surface model of D. athene sp. n. holotype (CASENT0764088). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/8486543f757b484d895 2a7dd01c8d733.

seta inserted in apical pit; mesobasitarsus short, about as long as tarsomeres II-IV taken together.

Petiolar node moderately to strongly attenuated dorsally, about 3.7 times higher than broad (LPeI 286–500). In profile, anterior face of node convex, apex broadly peaked, posterior face sloping posteroventrally. In dorsal view, petiole about 3–5 times wider than long (DPeI 300–500); sides divergent posteriorly, posterior margin slightly concave, anterior margin nearly straight. In anterior view, petiolar outline very wide, pentagonal, edges and apex slightly rounded but distinct; in oblique anterior view, anterior face flat; in ventral view approximately rectangular, sides diverging posteriorly; subpetiolar process large, lobate, apex rounded; petiolar spiracles reniform in ventral view.

Abdominal segment 3 roughly campaniform, tergite prolonged anteriorly pasted anterior sternal margin, tergite widest just anterad end of segment, sternite sloping to convex in profile; AS 3 with scarce trace of medial carina; prora present as a very fine carina, shallowly concave in ventral view; AT4 about 0.85 the length of AT3 to slightly longer, usually approximately equal in length (ASI 85–103); AT4 almost perfectly hemidemispherical; AS 4 with anterior lip short but fairly broad, covering more than the one-third of the width of AS 3, anterior margin straight; successive abdominal segments short, telescopic, often concealed.

Sculpture on head, dorsal mesosoma, and petiole regularly punctate-reticulate or foveolate-reticulate; on ventral head surface and lateral mesosoma becoming foveolate to punctate; lateral mesosoma with interspaces of foveolate forming rugulae, especially on lower surfaces; declivitous face of propodeum shallowly foveolate-reticulate to laterally rugulose; mandibles with fairly coarse piligerous punctae; frontal lamella and medial clypeus roughly granulate; AT3 shallowly punctulate-reticulate; AT4 with minute, dense piligerous punctulae, clearly shinier than AT3.

Setation mostly consisting of very fine, appressed white pubescence, similarly distributed on dorsal surfaces, dilute to absent on lateral surfaces of head and mesosoma; abdominal sternite 3 with longer, curved decumbent white setae; abdominal segments five through seven with longer, flexuous standing setae; appendages with only very fine, appressed white pubescence; ectal face of mandible with curved, appressed to decumbent setae; row of straight, stout setae on masticatory margin.

Color unicolorous luteous-orange to brown, usually brownish orange, upper surfaces often slightly infuscated.

Etymology

The Greek goddess Athene was fabled to have competed against a mortal woman named Arachne, whom the goddess punished for her hubris by transforming her into the first spider. Although the trophic biology of D. athene specifically is unknown, the species is named in reference to the known arachnophagic habits of its congeners. Additionally, Athene is archetypically portrayed bearing a helmet and a spear, reflecting the notably thick cuticle and prominent sting of Discothyrea .

Distribution and Biology

Discothyrea athene is known from various localities in East Africa including Rwanda, Uganda, Kenya, Tanzania, and Mozambique, where it occurs in forest and woodland, usually but not always below 1000 m ( Fig. 4D ). It has been collected in riparian forest, swamp forest, and near streams throughout its range, suggesting a possible preference for mesic habitats. The species lives in leaf litter.

Comments

This species is relatively unspecialized in character states but can only be confused with the potentially sympatric species from East Africa possessing a robust and stocky mesosoma (LMI2 92–103), such as D. damato , D. wakanda , D. schulzei , or D. venus . However, the latter is unique by having AT4 around 1.6 to 1.8 times longer than AT3 (ASI 158–183), and D. schulzei and D. wakanda have noticeable standing pilosity on the mesosomal and abdominal dorsa. The closest species is D. damato , but both can be differentiated by the eye size, the shape of petiole, and abdominal proportions.

Admittedly, the diversity of habitats and the elevational range of D. athene are rather unusual for species of the D. traegaordhi complex. Also, considering that there is some pronounced variation in size between series, it possible that the material considered as D. athene might represent more than one species. Unfortunately, the number of specimens from each locality is often limited, thus precluding a more in-depth analysis. Additional material from East Africa and molecular data could provide stronger evidence for heterospecificity, but based on the studied specimens we prefer to regard D. athene as one species for the present.

Variation

Discothyrea athene varies geographically in size, with specimens from Uganda and Rwanda being generally larger (HW 0.38–0.42; WL 0.45– 0.53) than those from Kenya, Tanzania, and Mozambique (HW 0.33– 0.39; WL 0.38–0.50). This variation in size is not related to elevation. There is also some variation in color which may correspond to distribution: most individuals are similarly orange, while those from Rangiro are notably darker. The degree of attenuation of the petiolar node is also quite variable (DPeI 300–500; LPeI 286–500) but does not seem to be correlated to geography since specimens from the same series display pronounced differences.

Figures

Fig. 4. Maps showing the known distribution ranges of Afrotropical Discothyrea species.

Fig. 6. Diagnostic plate showing still images from surface volume renderings of the head in full-face view (the remainder of the body virtually removed). All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 7. Diagnostic plate showing still images from surface volume renderings of the head in profile (the remainder of the body virtually removed).All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation. Specimen codes are given inTable 1.

Fig. 8. Diagnostic plate showing still images from surface volume renderings of the right mandible in dorsal view (the remainder of the body virtually removed).All Afrotropical species are shown,species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 9. Diagnostic plate showing still images from surface volume renderings of the mesosoma in profile (the remainder of the body virtually removed). All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 10. Diagnostic plate showing still images from surface volume renderings of the body in dorsal view with focus on mesosoma.All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation. Specimen codes are given inTable 1.

Fig. 11. Diagnostic plate showing still images from surface volume renderings of the posterior propodeum in posterior view (the remainder of the body virtually removed). All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation. Specimen codes are given inTable 1.

Fig. 12. Diagnostic plate showing still images from surface volume renderings of the petiole and gaster in profile (the remainder of the body virtually removed).All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 14. Diagnostic plate showing differences in body pilosity. (A) D. mixta (CASENT0235473),(B) D. oculata (CASENT0235467),(C) D. aisnetu (CASENT0235475), (D) D.athene (CASENT0235476),(E) D.chimera (CASENT0235471),(F) D.damato (CASENT0247362),(G) D.dryad (CASENT0247371),(H) D.gaia (CASENT0247040), (I) D. gryphon (CASENT0247367), (J) D. hawkesi (CASENT0235470), (K) D. kalypso (CASENT0235468), (L) D. maia (CASENT0790541), (M) D. michelae (CASENT0235469), (N) D. patrizii (CASENT0235472), (O) D. penthos (CASENT0247383), (P) D. poweri (SAM-ENT-0011509), (Q) D. schulzei (CASENT0247370), (R) D. traegaordhi (CASENT0790122), (S) D. venus (CASENT0247017), (T) D. wakanda (CASENT0790326).With the exception of F, L, R,T, all other images are from https://www.antweb.org—photographers Michele Esposito and Will Ericson.

Fig. 25. Stacked digital color images of D. athene sp. n. (CASENT0235476 - from https://www.antweb.org, photographer Will Ericson). (A) body in profile, (B) body in dorsal view, (C) head in full-face view.

Fig. 26. Still images from shaded surface display volume renderings of D. athene sp. n. holotype (CASENT0764088) showing virtually segmented body parts. (A) Body in dorsal view, (B) body in profile, (C) head in full-face view, (D) head in dorsal view, (E) head in anterodorsal view, (F) head in anterior view, (G) head in profile, (H) head in ventral view, (I) posterior propodeum in posterior view, (J) petiole in profile, (K) petiole and gaster in profile, (L) petiole in dorsal view, (M) petiole in anterior view, (N) petiole oblique anterior view, (O) gaster in dorsal view, (P) petiole in ventral view, (Q) abdominal sternite 3 in ventral view, (R) mesotibia and mesotarsus in anterior view.