The morphology and molecular phylogenetics of some marine diatom taxa within the Fragilariaceae, including twenty undescribed species and their relationship to Nanofrustulum, Opephora and Pseudostaurosira

Dozens of monoclonal cultures of small-celled araphid diatoms from brackish or marine habitats worldwide were analyzed using morphological observations (light and electron microscopy) and molecular data (nuclear-encoded small subunit ribosomal RNA and chloroplast encoded rbcL and psbC). As a result, we established one new genus Gedaniella, distinguished by a shared morphological character (occlusions of branched volae, projecting from the apical sides of the areolae) and some molecular data, including five new species: G. alfred-wegeneri, G. arenaria, G. boltonii, G. panicellus, G. paucistriata and three new combinations: G. flavovirens, G. guenter-grassii and G. mutabilis. Additionally we describe eleven novel species within the existing genus Serratifera: S. andersonii, S. brevis, S. clavata, S. corallina, S. namibica, S. nosybeana, S. parkii, S. punctata, S. rhombica, S. sourniae, S. takanoi and one new combination S. opephoroides. Furthermore, five new taxa or combinations were described within other genera: such as Cratericulifera crinigera, Nanofrustulum wachnickianum, Plagiostriata baltica, Pseudostaurosira madagascariensis and Stauroforma rinceana. Detailed descriptions for established species are also provided: Nanofrustulum shiloi, Opephora pacifica and Pseudostaurosira elliptica. This study strongly suggests that the complete biodiversity of small-celled araphids is still far from known, and many species currently placed in Opephora and Pseudostaurosira need to be further re-investigated.