Orthetrum umbratum Dijkstra & Mézière, 2015

Dijkstra, Klaas-Douwe B., Kipping, Jens & Mézière, Nicolas, 2015, Sixty new dragonfly and damselfly species from Africa (Odonata), Odonatologica 44 (4), pp. 447-678 : 641-644

Orthetrum umbratum Dijkstra & Mézière sp. nov. – Shadow Skimmer (Type Photo 53, Photo 68, Fig. 31)

Taxonomy

Morphologically and ecologically similar to O. saegeri (see O. agaricum sp. nov.), but differs clearly in the shape of the hamule. May genetically be distinct from sympatric O. saegeri , but this is not entirely resolved (see below).

Material studied

Holotype ♂. RMNH.INS.506140 , Gabon, Haut-Ogooué Province, Moanda- Lastoursville road about 4 km after Moukoumbi , roadside stream, swamp, forest and spring, 532 m a.s.l. (1.0836 ° S 12.8923 ° E), 10 -iii- 2012, leg. N. Mézière, RMNH .

Further material. GABON (Haut-Ogooué Province): 5 ♂ ( RMNH.INS.506180 ), as holotype, RMNH . 1 ♂ ( RMNH.INS.508810 ), Bakoumba, Parc de la Lékédi, Module 3 , sandy forest stream (1–2 m wide, 20 cm deep) with bordering seep, sources and ponds, 577 m a.s.l. (1.7437 ° S 12.9354 ° E), 08-v- 2013, leg. N. Mézière & J. Renoult, RMNH .

Genetics

Five unique haplotypes (n = 7) are quite distinct from five of O. saegeri (n = 6), but aside from three samples of O. umbratum this group includes one of O. lusinga sp. nov., one of O. saegeri from central Congo-Kinshasa, and two unverified samples of O. saegeri from Gabon ( Tree 8).

Male morphological diagnosis

Recalls the sympatric O. saegeri by (a) moderate size, Hw 27.5 –31.0 mm (n = 7); (b) the absence of cell-doublings in the radial planate and thus a single row of cells there; (c) all subcostal Ax dark; (d) medium-sized dark brown Pt that are about 11 % of Hw length, 3.0– 3.4 mm; (e) Hw base faintly yellow, but never with a dark brown patch; and (f) abdomen slender, although shorter than Hw. When not pruinose also similar by (g) the dorsa of S 4–7 with pairs of pale subapical spots that lie closer to the dorsal than lateral carinae, while S 8–10 are all dark. However, (1) the hook of the hamule tapers and curves gradually toward a sharp tip that is turned back- and outward, appearing like a claw or talon beside a rather narrow and distinctly higher lobe, with a wide space between the hook and lobe, and thus the overall shape is somewhat intermediate between O. hintzi and O. machadoi ( Fig. 31); and (2) the appendages are always wholly black and never (partly) pale in young specimens, although sympatric O. saegeri can be similarly dark.

Etymology

Latin “shaded” refers to the species’ deep forest habitat, which is unusual for the genus (neuter adjective).

Range and ecology

Replaces O. saegeri in south-eastern Gabon at the darkest and least disturbed rainforest pools with very much detritus, recorded at relatively high- er elevation between 530 and 580 m a.s.l ( Map 11). While O. saegeri often basks at the forest edge, O.umbratum only comes down to the ponds during bright sun in the two hours around noon.