Morphology and Phylogenetic Positions of Two Novel Gogorevia Species (Bacillariophyta) from the Han River, South Korea

This study reports two novel species, <i>Gogorevia contracta</i> sp. nov. and <i>G. recticentralis</i> sp. nov., which were isolated from freshwater environments in South Korea. Using an integrative taxonomic approach, we conducted morphological analyses using light microscopy and scanning electron microscopy, along with molecular phylogenetic investigations using <i>SSU</i> rRNA and <i>rbcL</i> gene sequences. Phylogenetic reconstructions highlighted the distinct characteristics of both species, confirming their classification within the genus <i>Gogorevia</i> and elucidating their evolutionary relationships. Morphologically, <i>G. contracta</i> was characterized by a bow-tie-shaped central area and circular depressions in the rapheless valve, whereas <i>G. recticentralis</i> exhibited a rectangular-to-wedge-shaped central area with parallel striae near the center of the raphe valve. Our findings highlighted the ecological significance of <i>Gogorevia</i> species and suggested their potential role as bioindicators of water quality in relatively unpolluted freshwater systems. Over the past decade, our research has focused on the taxonomic and ecological study of diatoms in the Han River system and identified 136 species, including nine newly described taxa. The findings of the present study contribute to a growing understanding of <i>Gogorevia</i> diversity, underscore the importance of region-specific diatom indices, and support the integration of morphological and molecular methods into diatom systematics.