Euglenids are a well-known group of single-celled eukaryotes, with phototrophic, osmotrophic and phagotrophic members. Phagotrophs represent most of the phylogenetic diversity of euglenids, and gave rise to the phototrophs and osmotrophs, but their evolutionary relationships are poorly understood. Symbiontids, in contrast, are anaerobes that are alternatively inferred to be derived euglenids, or a separate euglenozoan group. Most phylogenetic studies of euglenids have examined the SSU rDNA only, which is often highly divergent. Also, many phagotrophic euglenids (and symbiontids) are uncultured, restricting collection of other molecular data. We generated transcriptome data for 28 taxa, mostly using a single-cell approach, and conducted the first multigene phylogenetic analyses of euglenids to include phagotrophs and symbiontids. Euglenids are recovered as monophyletic, with symbiontids forming an independent branch within Euglenozoa. Spirocuta, the clade of flexible euglenids that contains both the phototrophs (Euglenophyceae) and osmotrophs (Aphagea), is robustly resolved, with the ploeotid Olkasia as its sister group, forming the new taxon Olkaspira. Ploeotids are paraphyletic, although Ploeotiidae (represented by Ploeotia spp.), Lentomonas, and Keelungia form a robust clade (new taxon Alistosa). Petalomonadida branches robustly as sister to other euglenids in outgroup-rooted analyses. Within Spirocuta, Euglenophyceae is a robust clade that includes Rapaza, and Anisonemia is a well-supported monophyletic group containing Anisonemidae (Anisonema and Dinema spp.), 'Heteronema II' (represented by H. vittatum), and a clade of Neometanema plus Aphagea. Among 'peranemid' phagotrophs, Chasmostoma branches with included Urceolus, and Peranema with the undescribed 'Jenningsia II', while other relationships are weakly supported and consequently the closest sister group to Euglenophyceae remains unresolved. Our results are inconsistent with recent inferences that Entosiphon is the evolutionarily pivotal sister either to other euglenids, or to Spirocuta. At least three transitions between posterior and anterior flagellar gliding occurred in euglenids, with the phylogenetic positions and directions of those transitions remaining ambiguous.

Department of Biology and Centre for Comparative Genomics and Evolutionary Bioinformatics Dalhousie University Halifax Canada

Department of Biology and Centre for Comparative Genomics and Evolutionary Bioinformatics Dalhousie University Halifax Canada; Department of Botany University of British Columbia Vancouver Canada

Department of Botany University of British Columbia Vancouver Canada

Department of Environment and Energy Engineering Kyungnam University Changwon Republic of Korea

Department of Zoology University of British Columbia Vancouver Canada

Institute of Evolutionary Biology Faculty of Biology University of Warsaw Poland

Institute of Parasitology Biology Centre Czech Academy of Sciences České Budějovice Czech Republic

Robert Cedergren Centre for Bioinformatics and Genomics Biochemistry Department Université de Montréal Montréal Canada

Unité d'Ecologie Systématique et Evolution CNRS Université Paris Saclay Orsay France; Department of Zoology University of British Columbia Vancouver Canada

Citace poskytuje Crossref.org

On the possibility of yet a third kinetochore system in the protist phylum Euglenozoa

Euglena International Network (EIN): Driving euglenoid biotechnology for the benefit of a challenged world

Heterotrophic euglenid Rhabdomonas costata resembles its phototrophic relatives in many aspects of molecular and cell biology

Single-cell genomics unveils a canonical origin of the diverse mitochondrial genomes of euglenozoans

Euglenozoa: taxonomy, diversity and ecology, symbioses and viruses