HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Gontcharov, A. A. Articles by Melkonian, M. PubMed Articles by Gontcharov, A. A. Articles by Melkonian, M. Agricola Articles by Gontcharov, A. A. Articles by Melkonian, M.

In search of monophyletic taxa in the family Desmidiaceae (Zygnematophyceae, Viridiplantae): the genus Cosmarium¹

Botanisches Institut, Lehrstuhl I, Universität zu Köln, Gyrhofstr. 15, D-50931 Köln, Germany

ABSTRACT

Nuclear-encoded small subunit (SSU) rDNA, 1506 group I introns, and chloroplast rbcL genes were sequenced from 97 strains representing the largest desmid genus Cosmarium (45 spp.), its putative relatives Actinotaenium (5 spp.), Xanthidium (4 spp.), Euastrum (9 spp.), Staurodesmus (13 spp.), and other Desmidiaceae (Zygnematophyceae, Streptophyta) and used to assess phylogenetic relationships in the family. Analyses of single genes and of a concatenated data set (3260 nt) established 10 well-supported clades in the family with Cosmarium species distributed in six clades and one nonsupported assemblage. Most of the clades contained representatives of at least two genera highlighting the polyphyletic nature of the genera Cosmarium, Euastrum, Staurodesmus, and Actinotaenium. To enhance resolution between clades, we extended the data set by sequencing the slowly evolving chloroplast-encoded large subunit (LSU) rRNA gene from 40 taxa. Phylogenetic analyses of a concatenated data set (5509 nt) suggested a sister relationship between two clades that consisted mainly of Cosmarium species and included C. undulatum, the type species of the genus. We describe molecular signatures in the SSU rRNA for two clades and conclude that more studies involving new isolates, additional molecular markers, and reanalyses of morphological traits are necessary before the taxonomic revision of the genus Cosmarium can be attempted.

Key Words: Actinotaenium • clades • Cosmarium • Desmidiaceae • Euastrum • molecular phylogeny • molecular signatures • polyphyly • taxonomy

Received for publication 7 February 2008. Accepted for publication 11 June 2008.

FOOTNOTES

¹ The authors thank P. C. Silva and F. A. C. Kouwets for discussion on the type species of Cosmarium. This work was supported by DFG grant ME-658/26-1.

² Author for correspondence (e-mail: gontcharov{at}biosoil.ru); permanent address: Institute of Biology and Soil Science, 690022, Vladivostok-22, Russia.