Wood-Inhabiting Nematode, sp. n. (Nematoda: Aphelenchoididae) from David Elm, with Molecular Phylogeny of the Genus Based on Partial Mitochondrial Genomes.

A new nematode species, sp. n. is described in the bark beetle-elm tree association ( and var. ) in the Asian Pacific region of Russia. The new species belongs to the group of and is closest to . Its characteristics are as follows: lateral field with three incisures, body length 497-771 µm, post-uterine sac 3.6-5.4 times vulval body diam, 56 (39-66)% of vulva-anus distance, and spicule length 10.3 (9.5-12.5 µm). The new species differs from all species of the group in the closely situated P3 and P4 male caudal papillae and the GP5 small 'glandpapillae' pair on the butterfly-like papillae plate, in the set of P1, P2, P3, P4, GP5; vs. in all other species, the P4 papillae pair is absent in the pattern of P1, P2, P3, GP5. The phylogenetic position of sp. n. with other species of the group were reconstructed using the D2-D3 expansion segments of 28S and ITS rRNA gene sequence analysis. Sequences of twelve mitochondrial protein-coding genes of sp. n., and were obtained in this study. Phylogenetic relationships among eighteen species based on the analysis of the mtDNA sequence dataset are provided and discussed. A modified diagnosis of the group is proposed.