Luticola edaphica sp. nov. (Diadesmidaceae, Naviculales) from the Soil of the Russian Far East (Primorsky Territory, Russia)

The naviculoid genus <i>Luticola</i> exhibits a high degree of morphological convergence, complicating species delimitation when based solely on traditional morphometrics. Here, we describe <i>Luticola edaphica</i> sp. nov., a new species isolated from the forest soils of Mount Sestra (Primorsky Territory, Russian Far East) using an integrative taxonomic approach (phylogenetic, morphological, ultrastructural, and life cycle data). Molecular phylogenetic analysis, based on the chloroplast <i>rbc</i>L gene, placed the new strain within the <i>Luticola</i> clade, showing the closest affinity to <i>L. tenera</i>. However, <i>L. edaphica</i> is distinguished from similar <i>Luticola</i> species by a unique combination of morphological traits (structure of the valvocopula, maximal valve length and width, position and number of striae in 10 µm, central area, and distal raphe ends). A comprehensive study of its life cycle revealed that <i>L. edaphica</i> is homothallic and capable of both cis- and trans-anisogamy, with the latter being reported for the genus for the first time.