Marshallya, Roháček, 2018

Roháček, Jindřich, 2018, First Anthomyzidae (Diptera) from China: a new genus, six new species and new records, Acta Entomologica Musei Nationalis Pragae 58 (1), pp. 35-76 : 37-40

Marshallya gen. nov.

Type species. Marshallya platythorax sp. nov., here designated.

Diagnosis. (1) Head slightly longer than high. (2) Eye large, very convex, elongately ellipsoid, with longest diameter oblique. (3) Frons narrow, flattened and medially slightly depressed; (4) frontal triangle short and shining. (5) Frontal lunule reduced, indistinct. (6) Occiput strongly concave. (7) Vertex with silvery grey microtomentose stripes lateral to ocellar triangle. (8) Antenna geniculate between pedicel and 1st flagellomere; pedicel simple, 1st flagellomere strongly compressed laterally. (9) Arista ciliate (not pectinate) ( Fig. 2 ). (10) Palpus slender, with 1 distinct subapical seta and 2 apical setulae. Cephalic chaetotaxy: (11) pvt small, convergent to parallel; (12) vte and/or posterior ors longest of cephalic setae; (13) vti shorter than vte but longer than oc; (14) 2 long ors, widely spaced – posterior in the middle of orbit, anterior close to fore margin of frons; 1 setula and 1 microsetula just in front of anterior ors; (15) postocular setulae minute, in single row; (16) 1 long vi and 1 subequally long subvibrissa; (17) peristomal setulae sparse but at least twice as long as postoculars. (18) Posteroventral corner of head (postgena) almost rectangled ( Fig. 3 ). (19) Antenna and face of similar colouring in both sexes (only slightly darker in female).

(20) Thorax narrower than head, subshining. (21) Mesonotum (but not scutellum) dorsally flattened ( Fig. 7 ). (22) Pleuron with dark longitudinal band at dorsal margin. Thoracic chaetotaxy: (23) 1 hu, 2 npl (anterior longer); (24) 0 prs; (25) 0 sa, 1 short pa; (26) 2 postsutural dc, both in prescutellar portion of scutum, only posterior long, anterior small; (27) ac microsetae in 4 rows in front of suture; (28) 2 sc, apical long, laterobasal short and weak; (29) 0 ppl; (30) 2 stpl, anterior almost as long as posterior, and a few setulae in dorsal half of sternopleuron. Legs: (31) femora and tibiae with dark annulus near knee; (32) f 1 of both sexes without ctenidial spine but with a comb of short anteroventral setae in distal two-fifths; (33) t 2 with distinct ventroapical seta; (34) f 3 of both sexes with posteroventral and anteroventral row of setae some of which in distal half are shortened and thickened. (35) Wing long and narrow; (36) wing membrane darkened, particularly subapically ( Fig. 1 ); (37) C with distinct spinulae among fine setulae on Cs 2 ( Fig. 4 ); (38) R 2+3 long, slightly sinuous, ending about twice as far from apex of R 4+5 than does M and bent towards C apically; (39) R 4+5 slightly bent apically; (40) R 4+5 and M distinctly convergent preapically but parellel apically; (41) M slightly sinuous; (42) dm cell narrow and relatively long; cross-vein r-m situated near its basal two-fifths to third; (43) CuA 1 medium long and almost reaching wing margin; (44) A 1 short but almost reaching wing margin; (45) anal lobe and alula reduced, both very narrow.

(46) Male abdomen very narrow, elongate. (47) T1 separate from T2; (48) T2–T5 large, long and broad, reaching laterally onto ventral aspect of abdomen, uniformly dark-pigmented. (49) S1–S5 narrower and very pale-pigmented. Male postabdomen: (50) T6 not developed (membranous); (51) S6–S8 fused dorsolaterally to form asymmetrical synsclerite; (52) S6 and S7 strongly asymmetrical, firmly fused and situated laterally, both without setae. (53) S8 very long, setose, less asymmetrical and situated dorsally.

Male genitalia ( Figs 8, 9, 11–22 ). (54) Epandrium relatively large, hemispherical, wider than long, densely setose, with 2 pairs of markedly longer setae. (55) Anal fissure large, high but relatively narrow. (56) Medandrium broad, not high, with submembranous dorsal part; (57) cercus medium-sized, sclerotized but dorsoventrally flattened, finely setose. (58) Gonostylus long, slender, with tapered apex and strongly bent medially, setose mainly on inner side, with micropubescence covering most of outer side. (59) Hypandrium robust, with flat lateral lobes well developed; (60) transandrium ( Figs 14, 15, 17 ) formed by simple medial sclerite, but its lateral robust part projecting in caudal process which is peculiarly connected with both pregonite and postgonite. (61) Pregonite elongate, very low, with 2 groups of setae, fused to hypandrium, only its anterior part projecting medially (see Fig. 15 ), posterior part very simple but fused with postgonite (and lateral caudal process of transadrium). (62) Postgonite unique because of its lateral position, absence of basal sclerite, short and complex form with several processes and fusion with pregonite and caudal process. (63) Basal membrane without sclerotized structures and ventrally incised. (64) Aedeagal part of folding apparatus ( Fig. 22 ) relatively short, provided with dark, radially arranged tubercles; (65) connecting sclerite ( Fig. 22 ) extremely robust and heavily sclerotized, distally dilated, darkened and angular. (66) Phallapodeme with basal part expanded into large flat wing-like lobes ( Fig. 19 ) embracing base of distiphallus. Aedeagus with (67) medium long (posteriorly projecting) phallophore and (68) distiphallus composed of voluminous largely membranous saccus and slender sclerotized filum. (69) Membrane of saccus overgrown by fine spines, mainly on its right side; (70) filum formed by 2 long, dark, slender and twisted band-like sclerites, but one of them shortened and ending far from apex. (71) Ejacapodeme small, with slender digitiform projection.

(72) Female abdomen also very elongate but with somewhat broader terga (T2–T5) and sterna (S2–S5) than in male. (73) Postabdomen ( Figs 23–25 ) relatively long, with terga and sterna (except S6) well sclerotized and dark-pigmented. (74) T6 and S6 relatively large, T6 dark, S6 pale. (75) T7 laterally extended and reaching ventral aspect but not fused with S7 and 7th spiracles free in pleural membrane; (76) S7 much smaller than S6, rounded, characteristically pigmented; (77) T8 simple, flat, with rounded corners; (78) S8 protruding posteromedially, with very small posteromedial incision. (79) Internal sclerotization of female genital chamber (uterus) well developed ( Figs 28, 30 ), formed by very complex (but symmetrical) posterior sclerites being posteroventrally fused to inner side of S8 and (80) 1 anteroventral, simply transversely ellipsoid annular sclerite. (81) Anterior part of uterus with voluminous vesicular kidney-shaped ventral receptacle ( Fig. 28 ). (82) Accessory glands of usual form, on short simple (non-dilated) ducts. (83) Spermathecae (1+1) shortly pyriform ( Figs 28, 29 ), with well-developed sclerotized cervix and some grain-like spinulae on smooth body surface; spermathecal duct relatively short. (84) T10 relatively large, rounded, partly dark, with 1 pair of dorsomedial setae; (85) S10 slightly smaller than T10, simply semicircular, micropubescent besides fine setulae. (86) Cerci moderate but robust, with comparatively short, fine and abundant setae, none of which is enlarged.

Discussion. The combination of diagnostic characters of Marshallya gen. nov. (as listed above) is unique within the Anthomyzidae . These characters include external features shared with Amygdalops Lamb, 1914 and its relatives (while lacking most of their synapomorphies in the male and female terminalia), plesiomorphies widespread among anthomyzid genera and, most significantly, apomorphies unique within the whole family Anthomyzidae .

The type species of Marshallya externally closely resembles species of the Old World tropical genus Amygdalops and the related Afrotropical genus Margdalops Roháček & Barraclough, 2003 in having very convex ellipsoid eyes, narrow frons, 2 long widely spaced ors, strongly concave occiput, pleuron with dark dorsal band, wing with subapical darkening, narrow and relatively short dm cell, reduced anal lobe and alula etc. With Amygdalops it also shares vti shorter than vte, reduced frontal lunule, dc macrosetae in prescutellar position and shortened CuA 1 (cf. ROHÁČEK 2004, 2008), and with Margdalops vertex with silvery microtomentose stripes and the ciliate (not pectinate) arista (see ROHÁČEK & BARRACLOUGH 2003). However, more detailed study of the type species of Marshallya revealed substantive morphological dissimilarities with both genera discussed above, particularly with unique structures of the male and female terminalia (see below). The new genus differs from them also in several external characters, particularly in having the dorsally flattened mesonotum, reduced thoracic chaetotaxy (prs, sa, ppl absent, pa short), both male and female with rows of shortened thickened setae on f 1 (anteroventrally) and f 3 (both anteroventrally and posteroventrally), C with distinct spine-like setae among fine setulae and very elongate slender abdomen. It is notable that some of these characters can be found as homoplasies in distinctly non-related genera, e. g. the flattened mesonotum in the genus Typhamyza Roháček, 1992 , the reduced thoracic chaetotaxy in Anagnota Becker, 1902 and Cercagnota Roháček & Freidberg, 1993 (see ROHÁČEK 2006) and f 1 with anteroventral row of thicker setae in the Afrotropical genus Barbarista Roháček, 1993 (see ROHÁČEK 1993).

Nevertheless, the most important autapomorphies that characterize Marshallya can be seen in the male genitalia and female postabdomen as follows: (58) gonostylus elongate but strongly bent medially ( Fig. 9 ); (60) transandrium with robust lateral parts, each projecting in caudal process which is uniquely connected with both pregonite and postgonite; (62) postgonite in unusual lateral position, lacking the basal sclerite, of short and complex form with several processes and fused with (posterior part of) pregonite and (lateral) caudal process (see Figs 16, 17 ); (63) basal membrane without sclerotized structures and ventrally incised; (65) connecting sclerite ( Fig. 22 ) extremely robust and heavily sclerotized, distally dilated, darkened and angular; (66) phallapodeme basally with large symmetrical flat wing-like lobes embracing base of distiphallus ( Figs 19, 22 ); (70) filum of distiphallus with (plesiomorphic) 2 long band-like sclerites, but one them shortened and ending far from apex ( Fig. 21 ); (79) internal sclerotization of female genital chamber ( Figs 28, 30 ) well developed, formed by very complex (but symmetrical) posterior sclerites which are posteroventrally fused to inner side of S8 and (80) an anteroventral, simply transversely ellipsoid annular sclerite; (81) ventral receptacle voluminous, vesicular, kidney-shaped ( Fig. 28 ).

The relationships of the genus Marshallya have not yet been resolved. It is probable that its sister-group will be discovered among the largely unknown Oriental taxa of Anthomyzidae . Morphological and molecular distance (see Fig. 31 ) of M. platythorax to the externally similar Amygdalops species proved to be too large to demonstrate their close alliance. The new genus could possibly be a more distant relative of the Amygdalops clade (comprising Amygdalops, Margdalops and an unnamed Neotropical genus, cf. ROHÁČEK 2008) as is indicated by the shared external characters discussed above despite large molecular dissimilarity in the barcoding region of COI ( Fig. 31 ).

Species included. Marshallya platythorax sp. nov. (described below).

Etymology. The new genus Marshallya is dedicated to my friend, Steve A. Marshall (University of Guelph), the collector of its type species, world renowned Canadian dipterist and insect photographer. The name is an abbreviated conjunction of Marshall + [m] ya, gender feminine.

Figures

Figs 1–7. Marshallya platythorax sp. nov. and its habitat (China: Sichuan). 1 – wing (length ca. 3 mm); 2 – antenna, laterally; 3 – head and thorax, laterodorsally; 4 – detail of C with spine-like setae; 5 – copse of bamboo, habitat and probable host plant in the type locality (with Owen Lonsdale in front of it); 6, 7 – living adults on bamboo stem (body length ca 3.1 mm). Figs 1, 4 based on male paratype, Figs 2, 3 on male holotype. Photos by J. Roháček (1, 4), M. Tkoč (2, 3) and S. A. Marshall (5–7).

Figs 8–13. Marshallya platythorax sp. nov., male paratype (China: Sichuan). 8 – genitalia, laterally; 9 – external genitalia, caudally; 10 – f3 and t3 anteriorly; 11 – medandrium, anteriorly; 12 – apex of gonostylus, anterolaterally (widest extension); 13 – gonostylus, lateroventrally (widest extension). Scales = 0.5 mm (Fig. 10), 0.05 mm (Figs 12, 13), 0.1 mm (others). For abbreviations see p. 37.

Figs 14–22. Marshallya platythorax sp. nov., male paratype (China: Sichuan). 14–15 – hypandrial complex (14 – laterally; 15 – ventrally); 16 – postgonite and associated structures, laterally; 17 – transandrium, caudally; 18 – postgonite, caudally; 19 – phallapodeme, dorsally; 20 – ejacapodeme, different view than in Fig. 22; 21 – apex of filum, sublaterally; 22 – aedeagal complex, laterally. Scales = 0.05 mm (Fig. 16), 0.03 mm (Figs 18, 21), 0.1 mm (others). For abbreviations see p. 37.

Figs 23–27. Marshallya platythorax sp. nov., female paratype (China: Sichuan). 23–25 – postabdomen (23 – dorsally; 24 – laterally; 25 – ventrally); 26 – female f3, anteriorly; 27 – female f1, anteriorly. Scales = 0.2 mm. For abbreviations see p. 37.

Figs 28–30. Marshallya platythorax sp. nov., female paratype (China: Sichuan). 28 – genital chamber with 8th abdominal segment, laterally; 29 – spermathecae; 30 – internal sclerites of genital chamber and S8 (with setosity omitted), ventrally. Scales = 0.05 mm (Fig. 29) and 0.1 mm (others). For abbreviations see p. 37.

Fig. 31. Maximum likelihood tree outlining similarities of Amygdalops species and Marshallya platythorax based on the barcode region of COI.