Margdalops caligatus, Jindr & Rohác & ek & Barraclough, 2003

Jindr, Rohác, ich, ek & Barraclough, David, 2003, Margdalops, a new African genus of Anthomyzidae (Diptera), comprising six new species, African Invertebrates 44 (2), pp. 1-35 : 26-32

Margdalops caligatus sp. n.

( Figs 55–65 , 71 )

Type material: Holotype male, labelled: ‘ KENYA, 20 km S Kapsabet , 10.V.1991, A. Freidberg & Fini Kaplan’ ( TAUI, genit. prep.) . Paratypes: KENYA: 2 males 3 females, same data as holotype ; 2 females, Mt. ElgonLodge , Malaise trap, 1–6.xi.1983, A. Freidberg ( TAUI, 1 male 1 female SMOC; all with genit. prep.) .

Etymology: The name is derived from ‘ caliga ’ (L. = boot), referring to the boot-like shape of the male gonostylus.

Description: Male.

Total body length 2.14–2.38 mm. Body brown and pale yellow.

Head: As long as high or somewhat longer than high. Frons pattern as in M. bifilum , generally brown but its anterior fourth yellowish ochreous. Orbit brown, very sparsely microtomentose, mostly bare and shiny. Frontal triangle reaching to anterior fourth of frons; sparsely grey microtomentose (except bare ocellar triangle) as are the impressed and darker brown striae separating frontal triangle and orbit. Face pale to whitish yellow. Gena white and silvery microtomentose, with narrow brown ventral margin; postgena yellowish white. Mouthparts yellow, palpus whitish yellow. Chaetotaxy as in M. venustus , but pvt crossed; vti long, with apices meeting or crossed medially; oc slightly shorter than vti; 1 (more rarely 2) microsetulae in front of frontal triangle; subvibrissa distinctly weaker and shorter (half length of vi). Eye with longest diameter 1.4–1.5 times as long as shortest one. Gena slightly widened posteriorly; its minimum depth 0.05 times as long as shortest eye diameter.Antenna with ochreous scape and pedicel; 1st flagellomere dirty yellow to ochreous around base of arista to whitish yellow on apex; arista about 1.8 times as long as antenna, long ciliate.

Thorax: Brown dorsally, pale yellow ventrally. Mesonotum brown, with sparse microtomentum being white between dorsocentral lines in front of suture (only visible in very oblique lighting), dark grey laterally. Humeral and notopleural areas lighter brown. Pleura with brown dorsal band narrower than that of M. bifilum , otherwise yellow. Chaetotaxy as in M. venustus , but prs slightly shorter, pa distinctly longer and medial rows of ac microsetae reaching to posterior dc. Scutellum relatively flat dorsally. Legs yellow, femora and tibiae somewhat darker. Pedal chaetotaxies as in M. venustus ; f 3 with 13–14 setae in posteroventral row, 3–4 of them short and thicker than others. Wing ( Fig. 71 ) similar as in M. venustus , but marginal band shorter, R 4+5 less sinuate and apically subparallel to M, r-m situated anterior to middle of narrow dm cell and CuA 1 longer. Wing measurements: length 2.04–2.26 mm; width 0.61–0.66 mm, Cs 3: Cs

4

= 2.37–2.94, r-m/dm-cu: dm-cu = 5.00–5.57. Haltere brown, with darker knob.

Abdomen: With dark brown sclerites; preabdominal terga and sterna large and pleural membrane relatively narrow, as in M. bifilum . S3 and S4 largest of sterna, both as long as wide. S5 distinctly shorter and wider than S4, posteromedially emarginate. T6, S6– S8 also similar to those of M. bifilum .

Genitalia: Epandrium ( Figs 55, 56 ) moderately long, very densely setose, with 1 longer dorsomedial seta and 1 very long ventrocaudal seta.Anal opening large, suboval. Cercus large and unusually shaped, with frontocaudally flattened anteroventral part and ridgelike posteriorly projecting dorsal part ( Figs 55, 56 ). Medandrium ( Fig. 55 ) wide, very short medially. Gonostylus ( Figs 56, 57 ) boot-shaped in profile, with 2 blunt teeth on apex (cf. Fig. 55 ); its outer side with a few setulae but without micropubescence; inner side sparsely setose. Hypandrium relatively robust ( Fig. 59 ); transandrium straight ( Fig. 60 ); lateral sides and medial armature of basal membrane as in M. venustus . Pregonite ( Fig. 59 ) with simple posterior part and 2 groups of setae (6–7 in anterior and 2 in posterior group). Postgonite ( Fig. 59 ) small, slender, slightly bent, apically not very acute, with about 3 setulae, that in basal third longer; membrane attached internally to postgonite dark wavy striated. Aedeagal part of folding apparatus with dark lenticular tubercles; connecting sclerite ( Fig. 58 ) elongate, darker apically. Aedeagal complex ( Fig. 58 ) with robust phallapodeme having deeply bifurcate base. Saccus smaller than in M. venustus , membranous except for a pair of basal sclerites, with fine scattered tubercles and/or spinulae and a group of dark blunt spines near its middle. Filum shorter than in M. venustus and M. bifilum , formed by 2 stripe-like, basally fused sclerites, one longer and ending in curved apex. Ejacapodeme small, with slender projection ( Fig. 58 ).

Female differs from male as follows:

Total body length 2.30–2.70 mm.

Anterior fourth of frons and face darker, ochreous brown. Gena yellow and antenna ochreous with 1st flagellomere somewhat darker. f 3 with a posteroventral row of setae but only 2–3 of them thickened (cf. Fig. 65 ). Wing measurements: length 2.18–2.86 mm; width 0.65–0.85 mm, Cs 3: Cs 4 = 2.26–2.72, r-m/dm-cu: dm-cu = 4.40–5.62. Abdomen with preabdominal terga more transverse. S2 shorter than S3–S5, which are subequal in length and become slightly wider posteriorly, S5 being the largest.

Postabdomen ( Figs 63, 64 ) slighty longer than in M. venustus . T6 wide, posteriorly somewhat tapered, with short setae in front of unpigmented posterior margin. S6 wide, shorter and wider than S5, finely setose, emarginate posteromedially and lighter than S7. T7 narrow, but not emarginate anteriorly, with short and thick setae. S7 broader than long ( Fig. 64 ), posteriorly tapered, with rounded corners, very darkly pigmented and with a few fine setae (those in posterior row long). T8 dark, transverse, slightly wider posteriorly and with fine setae. S8 small, dark, with poorly delimited lateral margins. T10 small, rounded pentagonal, dark, with pale medial stripe ( Fig. 63 ). S10 slighty wider and paler than T10. Internal sclerotisation of genital chamber ( Fig. 62 ) composed of 3 pairs of twisted, more or less fused sclerites and of anterior faint ring-shaped, several times bent, structure. Ventral receptacle ( Fig. 62 ) cup-like, weakly sclerotised and terminating in apical finger-like projection. Accessory gland with terminally clavate duct. Spermathecae 1+1 ( Fig. 61 ) spherical, subequal in size, with a few minute spinulae near base and narrow (sometimes bent) sclerotised cervix. Cercus ( Fig. 63 ) longer and with longer setae than in M. venustus , pale pigmented.

Discussion: The new species forms a sister-group with M. bifilum sp. n. (see above). It resembles externally the latter species (see key), but differs in having a pale, silvery microtomentose gena and a narrower dorsal pleural band in addition to numerous features in the male genitalia (epandrium densely setose; distinctive male cercus; boot-like gonostylus; shortened filum of distiphallus) and the female postabdomen (S7 short, dark, with rounded corners; T10 dark, with medial light stripe) distinguishing it also from other Margdalops species. In contrast to other species treated here, the female of M. caligatus has some thickened short setae in a posteroventral row on f 3, but this feature also occurs in an unnamed species of the M. angustus -group from Kenya.

Biology: Adults were collected in May and June, with two females from a malaise trap. Distribution : The species is known only from Kenya .

NOTES ON PHYLOGENY AND BIOGEOGRAPHY

Cladistic analysis (refer to Appendix 1 for listing of characters) was used to resolve the relationships of Margdalops species studied. Amygdalops Lamb, 1914 , was found to be the sister-group of Margdalops gen. n.; the clade with this grouping is supported by 7 synapomorphies (see Fig. 72 , characters 1–7). One of these character states, viz. 5 – additional sclerite of the postgonite, was subsequently lost in the Margdalops venustus -group. The monophyly of the genus Amygdalops is supported by 9 apomorphies relative to only 6 synapomorphies uniting Margdalops species (cf. Fig. 72 ). The brown margined wing of Margdalops [character 19] is considered to be apomorphic and the unpatterned wing plesiomorphic, which, however, only occurs in the most primitive species of Amygdalops ( A. trivittatus Frey, 1958 ), while more advanced groups of Amygdalops have the wing ornamented (at least with a subapical spot), although never with a brown band along the anterior margin (cf. Rohác˘ek, in press).

The Margdalops species treated in this paper are divided into two well supported clades, one being the M. angustus -group [synapomorphies 23–26], the other the M. venustus -group [synapomorphies 27–32]. The M. angustus -group is considered to be more primitive, because species have more plesiomorphies and some species have less modified external male genitalia ( M. microcercus sp. n. in particular, see discussion under that species). The three species forming this group are retained in an unresolved trichotomy (owing to difficulties with the polarity determination), because no unambiguous synapomorphy has been revealed to demonstrate the sistergroup relationships of any of the species. In the other clade (formed by the M. venustus -group) M. venustus sp. n. was found to be the sister-group of the remaining sister-pair formed by M. bifilum sp. n. and M. caligatus sp. n., although the monophyly of the latter group is not very strongly supported [cf. characters 33- 36].

Presently, the genus Margdalops is only known from Africa. Despite the fact that all species described above are recorded only from South Africa, Kenya and Uganda, the genus probably is more widespread in the continent because further unnamed species were found to occur in Tanzania (2 females of an unusually large species in TAUI) and even in Nigeria (2 damaged males of a species of the M. angustus -group in NMWC). In Kenya 5 species of Margdalops were found ( M. microcercus , M. signatus , M. bifilum , M. caligatus spp. n., plus 1 unnamed species) belonging to both species-groups. The two species known from South Africa ( M. angustus , M. venustus spp.n.) also belong to the different species-groups. However, no more than 2 species have been collected from a single locality.

Margdalops appears to be associated mainly with indigenous forest in tropical Africa. In South Africa, its known distribution is predominantly in the warm, moist, eastern part of the country, which has rainfall in summer. The genus is, however, also recorded from cooler areas (Western Cape), as far west as Mossel Bay. Both South African species are recorded from a range of altitudes, including a variety of coastal habitats and montane areas (usually with afromontane forest).

Figures

Figs 55–60. Margdalops caligatus sp. n., male paratype (Kenya). 55. External genitalia, caudal view. 56. Same, lateral view. 57. Gonostylus, sublateral view (widest extension). 58. Aedeagal complex, lateral view. 59. Hypandrium and associated structures, lateral view. 60. Transandrium, caudal view. Scales: Fig. 57 = 0.05 mm, others = 0.1 mm. For abbreviations see text.

Figs 61–65. Margdalops caligatus sp. n., female paratype (Kenya). 61. Spermathecae. 62. Genital chamber with internal sclerites + 8th abdominal segment, lateral view. 63. Female postabdomen, dorsal view. 64. Same, ventral view. 65. f3, posterior view. Scales: Figs 61, 62 = 0.1 mm, others = 0.2 mm. For abbreviations see text.

Figs 69–71. Wings of Margdalops species. 69. M. venustus sp. n., male paratype (S. Africa), 70. M. bifilum sp. n., male paratype (Kenya), 71. M. caligatus sp. n., male paratype (Kenya). Scale = 0.5 mm.

Fig. 72. Cladogram showing the inferred relationships of species of Margdalops gen. n.