Zygonyx annika Dijkstra

Dijkstra, Klaas-Douwe B., Kipping, Jens & Mézière, Nicolas, 2015, Sixty new dragonfly and damselfly species from Africa (Odonata), Odonatologica 44 (4), pp. 447-678 : 661-665

Zygonyx annika Dijkstra sp. nov. – Annika’s Cascader (Type Photo 58, Photo 75, Fig. 35)

Taxonomy

Variation in markings and male genitalia suggests that a complex exists of species similar to Z. flavicosta (Sjöstedt, 1900) , but thus far only Z. geminuncus Legrand, 1997 has been separated. Morphology and COI data suggest that at least six species are involved, with two or even three occurring in close proximity. Variation among specimens nearest to the true Z. flavicosta is so great that we only name three species that can be separated from sympatric relatives by both genetics and morphology ( Tree 10). The present taxon is known only from a pair caught in copula, which overlaps geographically with morphologically and genetically distinct populations that were identified as Z. flavicosta .

Material studied

Holotype ♂. RMNH.INS.503187 , Sierra Leone, Eastern Province, 40 km SW of Kenema, Moa River at Tiwai Island , forested island in large river with rocky rapids ( Photo 75), 122 m a.s.l. (7.551 ° N 11.3549 ° W), 14 -iii- 2011, leg. K.-D.B. Dijkstra, RMNH . The right Hw and leg are aberrant in shape, which is probably a developmental defect.

Further material. SIERRA LEONE (Eastern Province): 1 ♀ ( RMNH.INS.503188 ), in copula with holotype, RMNH .

Genetics

One unique haplotype (n = 2) is distinct and nearer to Z. dionyx sp. nov. and Z. geminuncus than the morphologically similar Z. flavicosta ( Tree 10).

Male morphological diagnosis

Belongs to the flavicosta -complex by (a) the modest size, Hw 36.5 mm (n = 1); (b) the moderately dense venation, with 13 ½– 14 Ax in Fw; (c) the largely black hind legs; (d) the pointed and forward-curved apex of the anterior lamina ( Fig. 35); and (e) the pale dorsal band on S 7 that stands out against the largely dark S 5–6. Differs from the sympatric Z. flavicosta by (1)the dorsum of the eyes being deep reddish brown, contrasting with their greyish underside, rather than uniformly grey-blue; and (2) the shorter hook of hamule, which is less than a third as long as the hamule is wide ( Fig. 35). Also differs from Z. flavicosta from Sierra Leone, Liberia and Gha- na by (3) the Hw membrane being darkly stained and not clear beside the membranule; (4) the more continuous pale thoracic markings, the stripe on the metepisternum not being broken between the metastigma and wing base, while that on the metepimeron is not invaded by black posteriorly to appear T-shaped; and (5) the straighter cerci ( Fig. 35).

Etymology

Named in honour of Dr Annika Hillers, who advanced research on the Gola rainforest ecosystem and enabled the author to make his contribution (noun in apposition).

Range and ecology

Rocky fast-flowing section of the large Moa River in Sierra Leone, flanked by gallery forest and about 120 m a.s.l. Similar adults and possible exuviae were seen near Kenema 35 km upstream, but Z. flavicosta is sympatric and possibly syntopic.