Review of Euseius Wainstein (Parasitiformes: Phytoseiidae) in Türkiye: An integrative taxonomic approach using morphological and molecular data with a new combination Euseius degenerans (Berlese)1

Despite the significant abundance of four Euseius species, across different regions of the Western Palearctic, including Türkiye, studies on their systematics have been limited to either morphological or molecular methods, with no studies using both approaches together. This study comprehensively evaluates these four species, using both detailed morphological characteristics and molecular analyses based on ITS DNA fragments. We also examine Iphiseius degenerans (Berlese), previously classified in the monotypic genus Iphiseius, which still belongs to the subtribe Euseiina. Morphological analysis revealed that the measurements and other characters of these species perfectly match their original descriptions and redescriptions. Additionally, the anterolateral seta on trochanter I was modified into a subulate shape in all five species. Molecular analysis showed minimal genetic divergence (0.000–0.009) within each Euseius species. Iphiseius degenerans did not exhibit genetic separation from other Euseius species, supporting its reclassification as Euseius degenerans comb. nov. Phylogenetic tree showed that each species formed distinct clades, confirming low intraspecific genetic divergence. Sequences of E. scutalis from Türkiye and Israel were genetically distinct from those from France and Spain. Although the genetic divergence was low (0.009), below the commonly used 2.8–3.0% species threshold, this may suggest the potential presence of two cryptic species. This integrative approach highlights the limitations of the currently used morphological classification system and emphasizes the need for more molecular studies to refine phytoseiid taxonomy.