Morphology and phylogenetic relationships of some Psychrophilic polar diatoms (Bacillariophyta)

Abstract

Nine psychrophilic polar diatom species within six genera (Chaetoceros, Fragilaria, Navicula, Nitzschia, Porosira and Stellarima) were found near King Sejong Station, MaxwellBay, King George Island, the Antarctic and near Dasan Station, Ny-？

lesund, Svalbard, the Arctic during November 1998 and January 2005. These psychrophilic diatoms all thrived at approximately 2℃under 25 ？

mol photons m-2 s-1. In this study, we tried to access diversity of psychrophilic polar diatoms cultivated in KCCPM and to establish their phylogenetic relationships among diverse diatoms based on morphological and molecular data. The 14 nuclear SSU rDNA and 18 plastid rbcL sequences were newly determined for this study and the data deposited in GenBank. Our SSU tree recovered very similar divergence patterns to the SSU tree by Medlin & Kaczmarska (2004). In the SSU tree, our species were placed in the deep branches of each clade, in general. Though phylogeny inferred from rbcL data were somewhat different from that from the SSU data at higher taxonomic levels within the diatoms, rbcL data were more powerful than SSU data between closely related taxa.