EVALUATING THE MORPHOSPECIES CONCEPT IN THE SELENASTRACEAE (CHLOROPHYCEAE, CHLOROPHYTA)¹

Abstract

Isolates of the genera Monoraphidium Kom.‐Legn., Ankistrodesmus Corda and Raphidocelis Hindák emend. Marvan et al. were cultured from two areas in Minnesota and North Dakota, USA. These isolates were identified to species level (when possible), using light microscopy and standard monographs and then characterized by 18S rDNA sequence analysis. Phylogenetic analyses indicated that in some cases, 18S rDNA sequences from these isolates were very similar, but not identical to the sequences of other isolates of the same morphospecies from different parts of the world. However, some isolates that were identified as the same species actually belong to different lineages within the Selenastraceae, whereas other isolates with identical or nearly identical 18S rDNA sequences possessed rather different morphologies. Overall, our data suggest that the application of a broad morphospecies concept to the Selenastraceae has resulted in an underestimation of the species diversity of this family and probably erroneous conclusions about the distribution of species.

Elliptochloris bilobata var. corticola var. nov. (Trebouxiophyceae, Chlorophyta), a novel subaerial coccal green alga

“…corticola may seem similar in traditional morphological features, the wide use of molecular characters has recently pointed to a general previously underestimated genetic and taxonomic diversity within traditional morphospecies. Such semi-cryptic or pseudo-cryptic taxa with subtle morphological differences have now been reported in diverse algal groups, including haptophytes (Saez et al 2003), diatoms (Amato et al 2007), prasinophytes (Slapeta et al 2006), as well as coccoid green algae (e.g., Fawley et al 2005b;Vanormelingen et al 2007). In addition, both varieties differ ecologically, since the former was originally identified as a phycobiont in temperate-zone high mountains (altitude of 2200 m a.s.l.)…”

Genotypic diversity of Dictyosphaerium-morphospecies (Chlorellaceae, Trebouxiophyceae) in African inland waters, including the description of four new genera.

“…Fawley et al (2004) studied the molecular diversity of coccoid and monadoid green algae in 20 lakes of North America and found 93 distinct SSU rRNA genotypes, 89 of those were new to science. Fawley et al (2005) evaluated the morphospecies concept in Selenastraceae and concluded that numerous cryptic species are hidden by one and the same morphotype. Pröschold & leliaert (2007), coesel &Krienitz (2008) andrindi et al (2010) discussed the state of the art in diversity and taxonomic conceptions in green algae and recommended studies using a polyphasic approach combining morphological and molecular phylogenetic methods.…”

Selenastraceae (Sphaeropleales, Chlorophyceae): rbcL, 18S rDNA and ITS-2 secondary structure enlightens traditional taxonomy, with description of two new genera, Messastrum gen. nov. and Curvastrum gen. nov.

“…The combination of cell size, shape, solitary or colonial lifestyle, the releasing process of the autospores and special habitat preferences, are considered to be species-specific (hindák 1977;komárek & Fott 1983). Based on these criteria, up to 100 species were described in various genera and included in this family (hindák 1977;hindák 1984;komárek & Fott 1983;FaWley et al 2006;krienitz et al 2011).…”

“…However, first studies in the 18S rDNA of the commonly observed genera in this family, e.g. Ankistrodesmus, Selenastrum, Monoraphidium, Quadrigula, Podohedriella and Kirchneriella, show that they form a monophyletic group within the Chlorophyceae (Fa- Wley et al 2006;krienitz et al 2011;krienitz et al 2001), apart from other members of Scenedesmaceae (FaWley et al 2006;krienitz et al 2001), Oocystaceae [which is now placed within the Class Trebouxiophyceae (Friedl 1995)] and Chlorellaceae (Friedl 1995;krienitz et al 2001). Since the onset of molecular phylogeny, several genera were excluded from the family due to their molecular traits, e.g., Closteriopsis was transferred to the Chlorellaceae and Hyaloraphidium is in fact a fungus (luo et al 2010;uStinova et al 2001).…”

“…For example, defined genera cluster polyphyletic on different clades within the Selenastraceae, e.g. Selenastrum bibraianum (type species of Selenastrum), and Selenastrum gracile belong to different phylogenetic lineages based on 18S rDNA phylogeny (FaWley et al 2006;krienitz et al 2001) but no taxonomic changes were made in the genus, since the authors suggested further studies with the family to ensure these findings.…”