Systematics of the Pseudagrion red-group from the Bismarck and Solomon archipelagoes (Odonata: Zygoptera: Coenagrionidae)

We examined the structural morphology, colour patterns and genetic relationships of representatives of the Pseudagrion red-group occurring on the Bismarck and Solomon archipelagoes. Five species-level taxa are recognised in this group, that we informally call the P. incisurum ‘complex’: P. bougainville sp. nov. from Bougainville; P. breviconis sp. nov. from Choiseul; P. incisurum Lieftinck from Guadalcanal and Malaita; P. lorenzi Gassmann from New Britain and Lihir Island; and P. simillimum sp. nov. from the New Georgia group in the Solomons. All of these species are brown-yellow to red damselflies, with a yellow face and with black pattern elements on the head, thorax and abdomen, and differ markedly from all other Papuan Pseudagrion by the shape of their male superior anal appendages. When viewed in lateral aspect, the appendages appear more or less parallel sided — at least not subconical — and apically rounded to almost truncate, not subacute or bilobed; and when viewed in a skewed dorsal aspect show a basal excavation anterior to a more or less developed subbasal to median process and a reflexed apical hook. Similarities in morphology supported by a molecular phylogeny based on mitochondrial and nuclear gene fragments indicate that these five species are closely related, but more extensive sampling of Pseudagrion species is required to confirm that they form a monophyletic group.