Abstract
Peritrichs are a major group of ciliates with worldwide distribution. Yet, its internal phylogeny remains unresolved owing to limited sampling. Additionally, ecological distributions of peritrichs are poorly known. We performed substantially expanded phylogenetic analyses of peritrichs that incorporated SSU rDNA sequences of samples collected from three continents, revealing a number of new relationships between and within major lineages that greatly challenged the classic view of the group. Interrogation of a dataset comprising new environmental sequences from an estuary and the open ocean generated with high throughput sequencing and clone libraries plus putative environmental peritrich sequences at Genbank, produced a comprehensive tree of peritrichs from a variety of habitats and revealed unique ecological distribution patterns of several lineages for the first time. Also, evidence of adaptation to extreme environments in the Astylozoidae clade greatly broadened the phylogenetic range of peritrichs capable of living in extreme environments. Reconstruction of ancestral states revealed that peritrichs may have transitioned repeatedly from freshwater to brackish/marine/hypersaline environments. This work establishes a phylogenetic framework for more mature investigations of peritrichs in the future, and the approach used here provides a model of how to elucidate evolution in the context of ecological niches in any lineage of microbial eukaryotes.
Highlights
Ectosymbiotic relationships or that occur in estuaries, offshore and extreme environments—have received much less attention
We hypothesized that interrogating new datasets generated by these methods from environments which are rarely represented in previous studies, combined with publicly available sequences with clear taxonomic designations and previously collected environmental sequences for peritrichs in Genbank, would permit a better assessment of the extent of the environmental diversity of peritrichs and their distribution among different environments[23,24]
The aims of the present study, were (i) to clarify the internal relationships of the subclass Peritrichia by increasing taxon sampling from a variety of habitats across large geographic regions; and (ii) to reveal the ecological distribution of taxa in a phylogenetic context based on environmental peritrich datasets encompassing a) new environmental data generated from samples collected from previous rarely represented environments, b) newly obtained, nearly full length sequences, and c) sequences with clear taxonomic designations as well as a wide array of environmental sequences from Genbank; and (iii) to describe a group I intron found in three populations of Vorticella gracilis collected from two geographically distant regions (China and Austria) that represents the first discovery of its type in ciliates
Summary
Ectosymbiotic relationships or that occur in estuaries, offshore and extreme environments—have received much less attention. The aims of the present study, were (i) to clarify the internal relationships of the subclass Peritrichia by increasing taxon sampling from a variety of habitats across large geographic regions; and (ii) to reveal the ecological distribution of taxa in a phylogenetic context based on environmental peritrich datasets encompassing a) new environmental data generated from samples collected from previous rarely represented environments, b) newly obtained, nearly full length sequences, and c) sequences with clear taxonomic designations as well as a wide array of environmental sequences from Genbank; and (iii) to describe a group I intron found in three populations of Vorticella gracilis collected from two geographically distant regions (China and Austria) that represents the first discovery of its type in ciliates
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