Revision of the Highly Specialized Ant Genus Discothyrea (Hymenoptera: Formicidae) in the Afrotropics with X-Ray Microtomography and 3 D Cybertaxonomy Author Hita-Garcia, Francisco Author Lieberman, Ziv Author Audisio, Tracy L. Author Liu, Cong Author Economo, Evan P. text Insect Systematics and Diversity 2019 2019-11-14 5 1 84 journal article 24900 10.1093/isd/ixz015 56172c62-3e7c-4ab7-83d4-1dd9f5c57eb5 3542130 F01A07B1-90C0-41A9-AFF8-1722885CE35C Discothyrea schulzei Hita Garcia & Lieberman sp. n. ( Figs. 4Q , 6Q , 7Q , 8Q , 9Q , 10Q , 11Q , 12Q , 14Q , 52 , 53 ; Supp. Video S17 [online only]) Type Material HOLOTYPE , pinned worker, RWANDA , Western , Rangiro , [ 2.39361 , 29.18278 ], 1800 m , collection code ANTC37497, from litter, 6.VIII.1973 ( P. Werner ) ( BMNH : CASENT0790121 ) . PARATYPES , two pinned workers with same data as holotype ( MHNG : CASENT0247365 , CASENT0790120 ); and one pinned worker with same data as holotype except collection code ANTC42124 and collected 10.VII.1973 ( P. Werner ) ( CASC : CASENT0247370 ) . 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 (CASENT0790121) 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 17). Nontype Material UGANDA : Bundibugyo , Semliki National Park , Kirumia River trail, 0.80909 , 30.09510 , 720 m , 20.VIII.2012 ( J. Longino ) ; Kabarole , Kibale National Park , Kanyawara Bioligcal Station , rainforest, 0.56437 , 30.36059 , 1510 m , 6.–16.VIII.2012 ( F. Hita Garcia ) . Diagnosis The following character combination distinguishes D. schulzei from the remainder of the complex: smaller species (WL 0.47–0.56); in profile frontal lamella with anterodorsal corner rounded, with conspicuous, large, basal fenestra; moderately long, distinct, well-spaced and almost entirely erect pilosity present on mesosoma and abdominal tergites; in dorsal view mesosoma conspicuously thick, robust and stocky (DMI 58–66; DMI2 95–100); anterolateral corner of gena weakly angled and not denticulate/dentate; mesosoma not extremely convex and propodeum denticulate/dentate; masticatory margin of mandible edentate; mesotibia without apicoventral spur; subpetiolar process long, dentate to spinose with rounded apex; AT4 around 1.1 to 1.2 times longer than AT3 (ASI 114–124); abdominal sternite 3 rounded, without any projecting lobe; anterior clypeal margin without conspicuous row of long, straight setae. Worker Measurements and Indices ( n = 6) EL 0.00–0.02; HL 0.46–0.54; HW 0.39–0.44; SL 0.25–0.29; PH 0.23–0.29; PW 0.29–0.35; DML 0.29–0.36; PrH 0.29–0.35; WL 0.47–0.56; HFL 0.26–0.33; PeL 0.07–0.08; PeW 0.18–0.21; PeH Fig. 53. Still images from shaded surface display volume renderings of D. schulzei sp. n. holotype (CASENT0790121) 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. 0.18–0.24; LT3 0.28–0.33; LT4 0.33–0.39; OI 0–3; CI 81–86; SI 50–56; LMI 49–55; DMI 58–66; DMI2 95–100; ASI 114–124; HFI 55–60; DPeI 234–270; LPeI 263–300. Worker Description Head longer than broad (CI 81–86), posterior head margin straight; posterodorsal corners of head rounded; in frontal view, sides of head converging gently anteriorly; eyes absent or very small (OI 0–3), an indistinct pigmented spot, situated slightly anterad one-third of the way between anterolateral corner of gena and posterior head margin, not visible in frontal view; frontal lamella lobate in profile, with anterodorsal corner rounded; lamella with conspicuous, large, basal fenestra; medial clypeus convex, lateral clypeus curving fairly strongly between antennal sockets and anterolateral corners of head, bearing short curved to erect setae. Antenna with moderately long scape (SI 50–56), scape moderately incrassate, gently bent; pedicel campaniform, slightly longer than broad; apparent antennomere count nine to eleven, flagellomeres basad apical club highly compressed, taken together only about as long as apical club. Ventral head with fairly low, sinuate preoccipital ridge with short, triangular anteromedial projection; median region of hypostoma triangular, arms only very slightly narrowed, squared apicolaterally; palpal formula not examined. Mandible edentate except for curved prebasal denticle; basal angle rounded; ectal face with carina confluent with masticatory margin for most of its length, leaving only a small depressed region containing prebasal denticle. Mesosoma weakly convex, pronotum only scarcely higher than propodeum; in dorsal view, mesosoma conspicuously thick, robust and stocky (DMI 58–66; DMI2 95–100), slightly narrowed posteriorly, pronotum not much wider than propodeum; pronotal humeri rounded; posterior propodeal margin concave; posterodorsal corners of propodeum rounded; declivitous face of propodeum distinctly concave in profile and oblique posterior view; propodeal spiracle inconspicuous, directed posterodorsally; propodeal lobes moderately well-developed, lobate. Legs short to moderately long (HFI 55–60); mesotibia without apicoventral spur; with small but distinct seta inserted in apicoventral pit; mesobasitarsus quite short, shorter than tarsomeres II–IV taken together. Model 17. 3D surface model of D. schulzei sp. n. holotype (CASENT0790121). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/c87c2fed1b87462a806 8867e5cf5e68d. Petiolar node not strongly attenuated dorsally, somewhat blunt in profile, about 2.6 to 3.0 times higher than long (LPeI 263–300); in profile anterior face of node sloping posterodorsally, apex rounded, posterior face sloping posteroventrally; in dorsal view, petiole rounded-rectangular, anterior margin and sides convex, posterior margin concave; about 2.3 to 2.7 times broader than long (DPeI 234–270); in anterior view, petiolar outline, edges and angles welldefined; in oblique anterior view, anterior face flat; subpetiolar process long, dentate to spinose with rounded or truncate apex. Abdominal segment 3 campaniform, tergite somewhat prolonged anteriorly past anterior sternal margin; sternite convex in profile; AS 3 with short, low anterior median ridge, with broad posterior lobe; prora carinulate, concave in ventral view; AT4 around 1.1 to 1.2 times longer than AT3 (ASI 114–124); AT4 hemidemispherical; AS 4 with broad, well-developed anterior lip, overlapping most of the width of AS 3, anterior margn straight in ventral view; successive abdominal segments short, telescopic, often concealed. Sculpture on head, mesosomal dorsum, petiole, and dorsal surface of AT3 coarsely foveolate-reticulate to alveolate, more sparsely so on lateral mesoma and abdominal segment 3; gena becoming somewhat more punctate to foveolate on ventral head surface; mandible roughly sculptured with piligerous punctulae; coarse sculpture persistent on frontal lamella and clypeus; rugulae present on lower portions of lateral mesosoma; declivitous face of propodeum longitudinally rugulose to costulate; AT4 distinctly smoother and shinier than AT3, with abundant but fine piligerous punctulae. Fig. 54. Stacked digital color images of D. traegaordhi Santschi,1914 neotype (CASENT0790122). (A) body in profile, (B) body in dorsal view, (C) head in full-face view. Fig. 55. Still images from shaded surface display volume renderings of D. traegaordhi Santschi, 1914 neotype (CASENT0790122) 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. Setation on head, mesosoma, petiole, and AT3 consisting of fine, dilute appressed pubescence on lateral surfaces, dorsal surfaces with distinct, abundant, erect white pilosity; abdominal sternite 3 and AT4 similarly setose, but pubescence longer and more distinct on lateral surfaces, and erect pilosity somewhat longer on AT4; successive abdominal segments with similar pattern, pubescence and pilosity equivalent to or slightly longer and more abundant than on AT4; scape and legs with evenly distributed, dense, appressed pubescence; ectal face of mandible with relatively short, curved, appressed to decumbent setae; masticatory margin with row of straight setae. Color rather dull testaceous-yellow to reddish, chestnut brown, appendages usually lighter. Etymology The name of the new species is a patronym dedicated to Arne Schulze from Frankfurt, Germany . The first author wants to thank him for his support and friendship during the time of this study. The specific epithet is given as a genitive noun. Distribution and Biology At present, D. schulzei is only known from Rangiro in Rwanda and Kibale Forest and Semliki National Park in Uganda ( Fig. 4Q ) . The former two localities are rainforest sites at elevations ranging from 1510 to 1800 m while the latter is moist semideciduous forest with patches of swamp forest between 670 and 760 m . Based on the collection data from the Kibale specimens, the species lives in leaf litter. We strongly suspect that the species will be found in more rainforests along the Albertine Rift in Burundi , Rwanda , and Uganda . Comments Discothyrea schulzei can be recognized based on its lack of mesotibial spurs, the presence of an extremely well-developed basal fenestra on the frontal lamella, its standing pilosity, size, and mesosomal shape. As mentioned above, D. schulzei is morphologically very close to D. damato . Indeed, they are only separable on the basis of setation. It is possible that they are conspecific and the differences in setation are just intraspecific variation. However, we prefer to propose them both as heterospecific for the following reasons. First, major pilosity phenotypes appear to be very stable at species level throughout the Afrotropical Discothyrea fauna. Second, and more importantly, D. damato and D. schulzei are Model 18. 3D surface model of D. traegaordhi Santschi, 1914 neotype (CASENT0790122). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/ fd0e0ae7fb63416c808 feb43 ce2a7235. found in sympatry and retain their different pilosity patterns in a very consistent way without any intermediate forms. Other species close to D. schulzei are D. dryad and D. wakanda since they agree in most characters. Nevertheless, they differ in body size (despite some overlap), profile of the frontal lamella, and the shape of the subpetiolar process; the mesosoma is similarly stocky in D. schulzei and D. wakanda but more elongate and posteriorly attenuate in D. dryad . The sculpture of D. schulzei is notably deeper than that of either D. dryad or D. damato . Variation Specimens from Rangiro have slightly longer pilosity than those from Kibale . Otherwise, there is no other noticeable intraspecific variation.