A new species of Placoneis Mereschkowsky (Bacillariophyceae: Cymbellales) from wet soils in southern Vietnam

A new diatom species of the genus Placoneis Mereschkowsky is described on the basis of molecular and morphological data. The new species, Placoneis asymmetricus Glushchenko, Kezlya, Kulikovskiy & Kociolek, sp. nov., is morphologically characterized by slightly asymmetrical valves along the apical axis based on light and scanning electron microscopy of the exterior and interior of valves. Molecular data, which are derived from live cells, are used for phylogenetic reconstruction based on 18S V4 rDNA and rbcL gene markers of taxa from the genus Placoneis and other diatoms in the order Cymbellales D.G.Mann. Comparisons with other morphologically and molecularly closely-related species are given.