Elucidating the evolution and diversity of Uroglena-like colonial flagellates (Chrysophyceae): polyphyletic origin of the morphotype
Abstract
The Uroglena-like morphotype represents a prototype of a colonial naked chrysophyte, comprising plastid-bearing cells that are arranged as the surface monolayer of the spherical colony. So far, insufficient molecular characterization appears to be the most significant brake on the modern taxonomic revision of this ecologically and morphologically coherent group of organisms.
The general aim of this work was to conduct a modern taxonomic revision of Uroglena-like flagellates by using combined molecular, morphological and ultrastructural methodology, complemented by exploring type localities of Uroglena volvox and Uroglenopsis americana in Europe and North America, respectively. On the basis of phylogenetic analysis of concatenated nuclear SSU rDNA and plastid rbcL sequences we show that Uroglena-like colonial flagellates form three genetically and morphologically distinct lineages within the Ochromonadales (Chrysophyceae), distinguished here as Uroglena, Uroglenopsis and Urostipulosphaera gen. nov.
The taxonomic status of the other chrysophyte genera with spherical colonies is discussed in light of our findings.