Discothyrea poweri ( Arnold, 1916 )

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 : 65-68

Discothyrea poweri ( Arnold, 1916)

( Figs. 4P , 6P , 7P , 8P , 9P , 10P , 11P , 12P , 13B , 14P , 50 , 51 ; Supp. Video S16)

Pseudosysphincta poweri Arnold, 1916: 162 , by monotypy. [Combination in Discothyrea by Brown, 1958a].

Type Material

HOLOTYPE, pinned worker, SOUTH AFRICA, Northern Cape, Kimberley , [-28.73, 24.77], 1225 m, 1912 (B. Power) ( SAMC: SAM- ENT-0011509) [examined].

Virtual dataset. Volumetric raw data (in DICOM format), 3D rotation video, still images of surface volume rendering, and 3D surface (in PLY format) of the nontype specimen (CASENT0764095) 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 species. In addition to the data at Dryad, we also provide a freely accessible 3D surface model at Sketchfab (Model 16).

Nontype Material

SOUTH AFRICA: Eastern Cape, Fern Kloof, vic. Grahamstown , 20.II.1969 (W.L. Brown) ; Eastern Cape, Hogsback , [−32.551, 26.949], ca. 1700 m, wet native forest, 26.II.1969 (W.L. Brown) ; Eastern Cape, Hogsback , [−32.551, 26.949], ca. 1700 m, indigenous evergreen forest, 26.III.1986 (H.G. Robertson) ; Eastern Cape, Signal Hill, vic. Grahamstown , [−33.3335, 26.549], ca. 750 m, pine native scrub, 18.II.1969 (W.L. Brown) ; Free State Province, Bloemfontein Botanical Garden , −29.05167, 26.21333, 1400 m, bushveld and riparian vegetation, 24.X.2011 (L. Almeida) ; KwaZulu-Natal, 75 km WSW Estcourt, Cathedral Peak Forest Station , −28.994, 29.282, 1500 m, podocarp forest, rotted stump of Cussonia spicata , 18.XII.1979 (S. & J. Peck) ; Western Cape, Cape of Good Hope N.R., Olifantsbos, nr. Skaife Centre , −34.2626667, 18.3855, 20 m, strandveld and mountain fynbos, 8.X.1998 (H.G. Robertson) ; Western Cape, Cape of Good Hope Nature Reserve , −34.2563, 18.3866, 19 m, X.2008 (G. Fischer & F. Hita Garcia) ; Western Cape, Cape Town, Kirstenbosch Botanical Garden , −33.988, 18.431, ca. 150 m, X.2008 (F. Hita Garcia & G. Fischer) ; Western Cape, Koeberg , −33.71667, 18.55, ca. 210 m, renosterbos vegetation, 4.XI.1994 (H.G. Robertson) ; Western Cape, Groeneweide Nature Walk , −33.95667, 22.53833, 197 m, indigenous forest, 20.X.2011 (L. Almeida) ; Western Cape, junction of Newlands Ravine Path and Contour Path , −33.9666, 18.4333, ca. 540 m, indigenous evergreen forest, 2.I.1997 (H.G. Robertson) ; Western Cape, Swellendam district, Grootvadersbosch , [-33.98471, 20.8084], 394 m, VII.1958 (J. Smith) .

Diagnosis

The following character combination distinguishes D. poweri from the remainder of the complex: generally larger species (WL Model 16. 3D surface model of D. poweri ( Arnold, 1916) (CASENT0764095). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/7fe9a5060b004ebe8f4 75424d89d770b.

0.67–0.84); comparatively long antennal scapes (SI 61–68); in dorsal view mesosoma very thin and elongate (DMI 45–52; DMI2 72–81) and distinctly narrowing posteriorly with pronotum much wider than propodeum; comparatively longer legs (HFI 61–69); mesotibia with conspicuous apicoventral spur; petiole relatively thick (DPeI 135–173; LPeI 152–194); abdominal terga without any standing pilosity, only with appressed pubescence.

Worker Measurements and Indices (n = 10)

EL 0.04–0.07; HL 0.59–0.70; HW 0.46–0.57; SL 0.37–0.47; PH 0.31–0.39; DML 0.43–0.55; PW 0.33–0.43; PrH 0.33–0.45; WL 0.67–0.84; HFL 0.42–0.55; PeL 0.13–0.18; PeW 0.23–0.29; PeH 0.26–0.30; LT3 0.38–0.47; LT4 0.41–0.50; OI 7–10; CI 77–84; SI 61–68; LMI 45–46; DMI 45–52; DMI2 72–81; ASI 105–110; HFI 61–69; DPeI 135–173; LPeI 152–194.

Worker Description

Head somewhat longer than broad (CI 77–84), posterior head margin convex, posterodorsal corners of head round, indistinct; in frontal view, sides of head slightly converging anteriorly; eyes relatively large (OI 7–10), round, setose, with several distinct ommatidia, situated almost halfway between anterolateral corner of gena and posterior head margin; eyes visible in frontal view; frontal lamella low, broadly triangular in profile, apex rounded; lamella quite thick apically, weakly translucent, thinner basally but without distinct fenestra; medial clypeus weakly to distinctly convex, slightly prolonged, lateral clypeus curving gently between antennal sockets and anterolateral corners of head; bearing short curved setae. Antenna with moderately long to longer scape (SI 61–68), scape only slightly expanded apically, gently bent; pedicel subcylindrical, longer than broad; apparent antennomere count nine to twelve, flagellomeres basad apical club compressed, taken together only slightly longer than apical club; apical club relatively narrow. Ventral head with low but clearly defined preoccipital ridge without anteromedian carina or with very slight anteromedial prolongation; medial region of hypostoma triangular, arms distinctively narrowed, spatulate apicolaterally; palpal formula not examined. Mandible with a slight preapical swelling and small prebasal denticle; basal angle rounded to squared; ectal face with carina originating at basal angle, becoming confluent with masticatory margin preapically, leaving narrow, curved depressed region.

Mesosoma elongate, gently sloping posteriorly to weakly convex, pronotum slightly higher than propodeum; occasionally metanotal area slightly bulging but not clearly demarcated; in dorsal view mesosoma very thin and elongate (DMI 45–52; DMI2 72–81) and distinctly narrowing posteriorly with pronotum much wider than propodeum; pronotal humeri narrowly rounded; posterior propodeal margin straight; posterodorsal corners of propodeum rounded; declivitious face of propodeum sloping, not concave in profile or oblique posterior view; propodeal spiracle relatively large, directed dorsolaterally; propodeal lobes well-developed, flangelike.

Legs moderately long and robust (HFI 61–69); mesotibia with distinct apicoventral spur; mesobasitarsus relatively short, about equal in length to tarsomeres II–IV taken together.

Petiolar node very thick, rounded-cuneate, not attenuated dorsally, about 1.5 to 1.9 times higher than broad (LPeI 152–194); in profile, anterior face of node sloping posterodorsally, apex thickly rounded, hence posterior face indistinct; in dorsal view, petiole campaniform to trapezoidal, sides divering posteriorly, about 1.4–1.7 times broader than long (DPeI 135–173); in anterior view, petiolar outline rounded, without clear faces; in oblique anterio view, anterior face flat or scarcely impressed medially. Subpetiolar process short, somewhat variable in shape but often rhomboid, sometimes with small digitate projection, with numerous decumbent to erect setae.

Abdominal segment 3 broadly campaniform, widest point just anterad end of segment; tergite more or less evenly convex, sternite poorly rounded to nearly flat in profile; AS 3 with low, broad median ridge, somewhat broader posteriorly in ventral view; prora without carina but strongly raised, concave in ventral view, anterolateral corners projecting more strongly; AT4 slightly longer than AT3 (ASI 105–110); AT4 hemidemispherical; AS 4 with poorly-developed anterior lip, overlapping median third of AS 3, anterior margin straight in ventral view; successive abdominal segments short, telescopic, often concealed.

Sculpture generally reduced; head, petiole, and abdominal segment 3 very shallowly punctulate-reticulate, somewhat more coarsely punctate on gena; mesosoma with sparse, very shallow punctulae; declivitous face of propodeum weakly rugulose to strigulate, particularly on lower half; mandible rather roughly sculptured with piligerous punctae; AT4 somewhat shinier than AT3, punctulae minute and very dense, tergite appearing shagreened.

Setation consisting of abundant but short and fine appressed pubescence more or less evenly distributed over entire body, slightly longer on abdominal terga; standing hairs entirely absent from dorsal surfaces; petiolar sternite and abdominal sternite 3 with fairly long, thick decumbent to suberect hairs; successive abdominal segments with dense, distinctly longer, standing pilosity; ectal face of mandible with abundant, curved, appressed to decumbent setae; masticatory margin with row of straight setae inserted on mesal face.

Color uniformly dull testaceous orange to matte brownish, sometimes with patchy infuscation on head, mesosomal, and abdominal dorsa.

Distribution and Biology

Discothyrea poweri appears to be relatively widespread in South Africa, ranging from the Western and Northern Cape to KwaZulu-Natal ( Fig. 4P ). It was found in a variety of habitats at elevations ranging from just above sea level to about 1700 m, which were predominantly forests, but also bushland, coastal shrub or botanical gardens. It has been collected from leaf litter, rotten wood, and under stones.

Comments

Discothyrea poweri is one of the more conspicuous species within the Afrotropical traegaordhi complex. Generally, it is a relatively large species with long legs, long antennae, and an exceptionally thick petiole. It is one of the largest species of the complex together with D. aisnetu and D. gaia . Compared to most other Afrotropical Discothyrea , the antennae of D. poweri appear especially elongate due to the relatively distinct flagellomeres and narrow apical club. The presence of a distinct mesotibial spur distinguishes it from most species of the complex, except for D. gaia and D. traegaordhi . The latter species is the only other member of the complex also occurring in South Africa, but it is easily distinguished from D. poweri on the basis of smaller body size (WL 0.51–0.57 vs. WL 0.67–0.84), a thinner petiole (DPeI 235–289 vs. DPeI 135–173; LPeI 236–313 vs. LPeI 152–194), and shorter antennal scapes (SI 50–55 vs. SI 61–68). Discothyrea gaia appears to be morphologically close to D. poweri but can be separated by the presence of standing pilosity on the abdominal terga. In addition, D. gaia also has shorter legs (HFI 54–58 vs. HFI 61–69) and a thinner petiole (DPeI 192–255 vs. DPeI 135– 173; LPeI 194–264 vs. LPeI 152–194). Nevertheless, it seems as if D. poweri belongs to a natural clade with D. gaia and D. traegaordhi , which is restricted in its distribution to Southern Africa.

Give the substantial variation in size, the wide range of habitats inhabited, and the limited material available for examination it is possible that D. poweri might actually be a complex of more or less cryptic species. However, due to very little other intraspecific variation we consider all the material listed here as one species with an unusual body size variation.

Variation

There is some noticeable size variation within this species (WL 0.67– 0.84) not seen in most other congeners. This size variation is also visible when comparing eyes. In larger specimens there are considerably more ommatidia than in smaller specimens, in which the eyes superficially appear smaller. However, after measuring it becomes clear that eye size is constant and not correlated with body size (OI 7–10). The shape of the subpetiolar process is also somewhat variable.

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. 13. Diagnostic plate showing still images from surface volume renderings of mesotibiae and mesotarsi with mesotibial apicoventral spur, if present, colorized in green. (A) D. gaia, (B) D. poweri, (C) D. traegaordhi, (D) D. dryad, (E) D. maia, (F) D. wakanda.

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. 50. Stacked digital color images of D. poweri (Arnold, 1916) holotype (SAM-ENT-0011509—from https://www.antweb.org, photographer unknown). (A) body in profile, (B) body in dorsal view, (C) head in full-face view.

Fig. 51. Still images from shaded surface display volume renderings of D. poweri (Arnold, 1916) (CASENT0764095) 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.