Molecular phylogenetics coupled with morphological analyses of Arctic and Antarctic strains place Chamaepinnularia (Bacillariophyta) within the Sellaphoraceae

Abstract

The diatom genus Chamaepinnularia was first published by Lange-Bertalot et Krammer in 1996 to accommodate several small species previously included within Navicula and Pinnularia. Despite its morphological similarity to those two genera, the family-level classification of Chamaepinnularia has been considered incertae sedis since its description almost three decades ago. We provide the first molecular characterisation (18S and rbcL) of the genus based on cultured polar strains and investigated its phylogenetic placement. Molecular data are complemented with observations on living cells, as well as detailed examination of oxidized material with light microscopy and scanning electron microscopy. The 12 investigated strains were morphologically identified as three taxa: two already described species (C. gerlachei, C. krookii) and one here newly described (C. australis sp. nov.). These species formed three separate, well-supported branches in the phylogeny. Our analyses placed Chamaepinnularia as a sister group to members of the Sellaphoraceae for which sequence data exist (i.e. Sellaphora, Fallacia, Rossia and Diprora). Based on the presence of hymenate areolae, a single Hshaped plastid with girdle appressed plates and the results of the phylogenetic trees, we propose the inclusion of Chamaepinnularia within the family Sellaphoraceae, which altogether form a supported monophyletic group.

Lipid degradation and photosynthetic traits after prolonged darkness in four Antarctic benthic diatoms, including the newly described species Planothidium wetzelii sp. nov.

“…The morphological and molecular analyses confirmed the assignment to four distinct species. The taxonomic identity of some strains was already published before (D288_003, D296_001, D300_015; Prelle et al, 2022 ; Schimani et al, 2023 ).…”

“…This species was first published by Van de Vijver et al ( 2010 ) from dry soil samples from James Ross Island, near the northeastern extremity of the Antarctic Peninsula, and has been observed until now just from maritime Antarctica (Kopalová et al, 2012 ; Sterken et al, 2015 ; Zidarova et al, 2016 ). A thorough examination of this strain can be found in Schimani et al ( 2023 ).…”