Integrative taxonomy of the genus Longidorus (Nematoda: Longidoridae) reveals two new species in the Mediterranean Basin

The needle nematode genus Longidorus comprises approximately 190 species of polyphagous plant ectoparasites distributed worldwide, some of which serve as vectors for plant viruses. However, the high species diversity and conserved morphology of these nematodes pose significant challenges for accurate species identification. To address this issue, we conducted an integrative taxonomic study across 264 sites in the Mediterranean Basin’s major olive-growing regions (Greece, Morocco, Italy, Portugal, and Spain), including nearby patches of natural vegetation. Herein, we describe two new species, Longidorus olearum sp. nov. and Longidorus morocciensis sp. nov., and report Longidorus oakgracilis in Portugal for the first time. We performed a comprehensive study that integrates morphological and morphometric traits with molecular data from nuclear ribosomal RNA genes (D2-D3 expansion segments of 28S, ITS1, and partial 18S) and mitochondrial DNA markers (COI). Phylogenetic analyses supported the delimitation of the new species, L. olearum sp. nov. and L. morocciensis sp. nov., and clarified the placement of three previously known species within the genus. Ribosomal and mitochondrial marker-based phylogenetic relationships revealed that most Longidorus species from the Mediterranean Basin clustered within subclades of Clade I. The phylogenetic positions of species showed strong consistency across lineages, aligning with previous studies on this genus. These findings expand our understanding of Longidorus biodiversity in the Mediterranean Basin and underscore the need for further intensive and extensive nematological surveys.