Molecular assessment of phylogenetic relationships in selected species/genera in the naviculoid diatoms (Bacillariophyta).: I.: The genus Placoneis

As part of a larger study to reconstruct evolutionary relationships within the naviculoid diatoms, phylogenetic analyses of several freshwater naviculoid species were performed using three different genes (SSU rRNA gene, LSU rRNA gene and rbcL gene), and the morphology of the sequenced species was investigated. This study focused on species of Placoneis, a genus that was separated from Navicula based on its chloroplast morphology, a feature that places it within the Cymbellales. The phylogenetic analyses also clearly place Placoneis in this order, but the relationships between the different genera varied with different genes. Navicula hambergii, whose allocation to Navicula sensu stricto was known to be wrong, is shown to belong to the genus Placoneis and is transferred to that genus. Its transfer is supported by both the phylogenetic analyses and the morphological investigation.