Systematic revision of Paralongidorus (Nematoda: Longidoridae) based on molecular and morphological evidence, with the description of a new species from Spain

Abstract The needle nematode genus Paralongidorus Siddiqi, Hooper & Khan, 1963 currently comprises 76 species of polyphagous plant ectoparasites with global distribution. Here, we revise the taxonomic ambiguities within the genus and update the polytomous key to facilitate species identification. Integrating ribosomal (D2–D3 expansion segments of 28S, ITS, partial 18S) and mitochondrial (partial COI mtDNA) markers, we reassess phylogenetic relationships within Paralongidorus and Longidorus . Our analyses reveal that Paralongidorus is paraphyletic, consistently resolving into two distinct subclades. We describe Paralongidorus cantabronavarrus sp. nov. from northern Spain, a species characterized by both molecular placement and morphological traits, including a uniquely anterior vulval position (V = 26–29%), the most extreme reported within the genus. This feature may represent a derived developmental adaptation, with potential ecological significance. Amphidial fovea morphology also shows evidence of convergent evolution, complicating generic boundaries. These findings challenge the validity of Longidoroides , reinforce the separation between Paralongidorus and Longidorus , and highlight the value of integrative approaches in resolving long-standing taxonomic uncertainties. The phylogenetic placement of P. cantabronavarrus sp. nov. is consistent across markers and aligns with previous studies. Overall, this work expands our understanding of Paralongidorus biodiversity in the Iberian Peninsula and underscores the need for further intensive nematological surveys in this area.