Plant Ecology and Evolution 152(2): 248-261, doi: 10.5091/plecevo.2019.1614
Taxonomy and diversity of a little-known diatom genus Simonsenia (Bacillariaceae) in the marine littoral: novel taxa from the Yellow Sea and the Gulf of Mexico
expand article infoByoung-Seok Kim, Andrzej Witkowski§, Jong-Gyu Park|, Chunlian Li, Rosa Trobajo#, David G Mann¤, So-Yeon Kim, Matt P Ashworth«, Małgorzata Bąk§, Romain Gastineau»
‡ Department of Oceanography, College of Ocean Science and Engineering, Kunsan National University, Gunsan 54150, Republic of Korea§ Palaeoceanology Unit, Faculty of Geosciences, Natural Sciences Education and Research Centre, University of Szczecin, Mickiewicza 16a, 70-383 Szczecin, Poland| Department of Marine Life and Applied Sciences, College of Ocean Science and Engineering, Kunsan National University, Gunsan 54150, Republic of Korea¶ Institute of Ecological Sciences, School of Life Sciences, South China Normal University, Guangzhou 510631, China# IRTA, Sant Carles de la Rapita, Spain¤ Royal Botanic Garden Edinburg, Edinburg, United Kingdom« University of Texas at Austin, UTEX Culture Collection of Algae, Department of Molecular Biosciences, 316 Biological Laboratories MS A6700, Austin, TX 78712, United States of America» FR CNRS 3473 IUML, Mer-Molécules-Santé (MMS), Le Mans Université, Avenue Olivier Messiaen, 72085 Le Mans CEDEX 9, France
Open Access

Background and aims – The diatom genus Simonsenia has been considered for some time a minor taxon, limited in its distribution to fresh and slightly brackish waters. Recently, knowledge of its diversity and geographic distribution has been enhanced with new species described from brackish-marine waters of the southern Iberian Peninsula and from inland freshwaters of South China, and here we report novel Simonsenia from fully marine waters.

Methods – New isolates of Simonsenia species were obtained from marine waters, the littoral zone of the Korean Yellow Sea coast and the Gulf of Mexico in Corpus Christi (Texas), and documented in LM, SEM and with DNA sequence data (plastid-encoded rbcL and psbC). Phylogenetic trees of raphid diatoms were constructed to assess the relationships of the new species and of the genus as a whole.

Key results and conclusions – Two novel species of Simonsenia (S. eileencoxiae and S. paucistriata) are described and a further putative taxon is characterized morphologically. The molecular phylogeny of the new Simonsenia species and previously sequenced species supports both the monophyly of the genus and its place within the Bacillariaceae. The Simonsenia clade clusters with clades composed of Cylindrotheca, Denticula and some Nitzschia spp. (including N. amphibia, N. frustulum, N. inconspicua). Hence Simonsenia is firmly positioned within the Bacillariaceae by molecular phylogenies, confirming its position within this group based on the possession of a canal raphe and its ultrastructure, and rejecting its classification within the Surirellaceae. Morphological data from the new Simonsenia species is typical for the genus, with a “simonsenioid” canal raphe type supported over the valve face with fenestral braces, alar canals connecting the canal raphe with the cell lumen, and the presence of fenestrae between the alar canals externally. Our results indicate unequivocally that the biogeography and the biodiversity of Simonsenia remain highly underestimated.

Bacillariaceae, diatoms, Gulf of Mexico, Simonsenia, molecular phylogeny, morphology, new marine species, Yellow Sea


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