Taxonomic reassessment of <i>Rotylenchus montanus</i> Vovlas, Subbotin, Troccoli, Liébanas and Castillo, 2008 (Nematoda: Hoplolaimidae): first reports from Spain and Ukraine

Spiral nematodes of the genus Rotylenchus (Nematoda: Hoplolaimidae) are obligate plant-parasites that affect a wide range of wild and cultivated hosts and are closely associated with plant roots in both agricultural and forested ecosystems. This study presents the first integrative taxonomic assessment of Rotylenchus montanus from forested regions in northern Spain and western Ukraine. Morphological and molecular analyses were conducted using nuclear ribosomal markers (D2–D3 expansion segments of 28S rDNA, ITS rDNA, and partial 18S rDNA) alongside the mitochondrial COI gene. Phylogenetic reconstructions confirmed that these populations are conspecific with the original population described from northern Italy and revealed a close relationship with previously reported R. montanus sequences from Italy, Belgium and Russia. The newly characterized populations exhibited low molecular diversity across all nuclear markers, consistent with parthenogenetic reproduction, as no males or sperm were detected. These findings extend the known geographical distribution of R. montanus, provide insights into its ecological preferences, and highlight the value of multilocus molecular approaches for nematode identification and biodiversity assessment.