Toward a monograph of non-marine Ulvophyceae using an integrative approach (Molecular phylogeny and systematics of terrestrial Ulvophyceae II.)

Tatyana Darienko,Thomas Pröschold

doi:10.11646/phytotaxa.324.1.1

Abstract

Phylogenetic analyses of SSU rDNA sequences have shown that coccoid and filamentous green algae are distributed among all classes of the Chlorophyta. One of these classes, the Ulvophyceae, mostly contains marine seaweeds and microalgae. However, new studies have shown that there are filamentous and sarcinoid freshwater and terrestrial species (including symbionts in lichens) among the Ulvophyceae, but very little is known about these species. Ultrastructural studies of some of them have confirmed that the flagellar apparatus of zoospores (counterclockwise basal body orientation) is typical for the Ulvophyceae. In addition to ultrastructural features, the presence of a “Codiolum”-stage is characteristic of some members of this algal class. We studied more than 50 strains of freshwater and terrestrial ulvophycean microalgae obtained from the different public culture collection and our own isolates using an integrative approach. Three independent lineages of the Ulvophyceae containing terrestrial species were revealed by these methods. Unexpectedly each of these lineages contained several isolates that morphologically developed a high degree of phenotypic plasticity, and included hidden phylogenetic diversity that let us to the description of several new genera and species.

Highlights

Most freshwater and terrestrial green algae belonged to the classes Chlorophyceae and Trebouxiophyceae (Ettl & Gärtner 1995)
Using an integrative approach in the first study of ‘Molecular phylogeny and systematics of terrestrial Ulvophyceae’, the species of the genus Desmochloris could be differentiated based on morphology, phylogeny, and molecular signatures using the secondary structures of ITS-1 and internal transcribed spacer region 2 (ITS-2)
Phylogenetic distribution of non-marine Ulvophyceae Phylogenetic analyses of the SSU rDNA sequences clearly revealed that all non-marine ulvophytes were distributed into two major lineages within the Ulvophyceae s.str.: Ulvales and Ulotrichales sensu Mattox et Stewart (Fig. 1)

Summary

Introduction

Most freshwater and terrestrial green algae belonged to the classes Chlorophyceae and Trebouxiophyceae (Ettl & Gärtner 1995). The type species of Desmochloris, D. halophila (Guillard, Bold et MacEntree) Watanabe, Kuroda et Maiwa, was described as Chlorosarcinopsis, a genus belonging to the Chlorophyceae, which is common in terrestrial habitats (Guillard et al 1975). As shown for D. mollenhaueri, terrestrial ulvophytes change morphology depending on different salinities (Darienko et al 2009), resulting in their difficult identification using traditional keys. To resolve this problem, robust molecular phylogenetic reconstruction and DNA barcoding can help to identify the microorganisms at generic and species levels and reveal hidden diversities among the Ulvophyceae

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