Four New Pinnularia Ehrenberg Species (Bacillariophyta) from Urban Freshwater Streams in South Korea

Abstract

This study reports the discovery of four novel Pinnularia species-P. latocentra sp. nov., P. rhombocentra sp. nov., P. seouloflexuosa sp. nov., and P. paristriata sp. nov.-from urban freshwater streams in South Korea. Species delimitation was achieved using a polyphasic approach that integrated light and scanning electron microscopy, ecological profiling, and molecular evidence from SSU rRNA and rbcL sequences. Each taxon was confirmed as morphologically and genetically distinct from its closest congeners. Our findings broaden the recognized diversity of Pinnularia in East Asia and demonstrate that urban streams, often regarded as degraded habitats, can harbor hidden diatom diversity and ecological complexity. By clarifying diagnostic traits, validating type material in a recognized repository, and aligning molecular and morphological evidence, this study contributes to a more robust taxonomy of Pinnularia. These results also highlight the importance of polyphasic taxonomy and the strategic inclusion of urban habitats in diatomological surveys and biodiversity assessments.