Barcodes Reveal 48 New Species ofTetrahymena,Dexiostoma, andGlaucoma: Phylogeny, Ecology, and Biogeography of New and Established Species

Abstract

Tetrahymena mitochondrial cox1 barcodes and nuclear SSUrRNA sequences are particularly effective at distinguishing among its many cryptic species. In a project to learn more about Tetrahymena natural history, the majority of >1,000 Tetrahymena-like fresh water isolates were assigned to established Tetrahymena species with the remaining assigned to 37 new species of Tetrahymena, nine new species of Dexiostoma and 12 new species of Glaucoma. Phylogenetically, all but three Tetrahymena species belong to the well-established "australis" or "borealis" clades; the minority forms a divergent "paravorax" clade. Most Tetrahymena species are micronucleate, but others are exclusively amicronucleate. The self-splicing intron of the LSUrRNA precursor is absent in Dexiostoma and Glaucoma and was likely acquired subsequent to the "australis/borealis" split; in some instances, its sequence is diagnostic of species. Tetrahymena americanis, T. elliotti, T. gruchyi n. sp., and T. borealis, together accounted for >50% of isolates, consistent with previous findings for established species. The biogeographic range of species found previously in Austria, China, and Pakistan was extended to the Nearctic; some species show evidence of population structure consistent with endemism. Most species were most frequently collected from ponds or lakes, while others, particularly Dexiostoma species, were collected most often from streams or rivers. The results suggest that perhaps hundreds of species remain to be discovered, particularly if collecting is global and includes hosts of parasitic forms.

Microbial grazers may aid in controlling infections caused by aquatic zoosporic fungi

“…Both Tetrahymena and Paramecium are common species in shallow waters [41,42,53], that, as we have shown, are capable of growth on Bd zoospores for limited to extended times.…”

“…Globally, Tetrahymena is common in shallow waters, living near sediments, where it consumes bacteria and other microbes [41,42]. These are the same habitats that Bd occupies.…”

A multidimensional approach to the expression of phenotypic plasticity

“…Especially the partitioning of variances showed substantial G × E interactions, with G × T being systematically greater than G × N , meaning that genotypes exhibited different reaction norms, especially to temperature. Those differences might reflect the environmental gradients encountered across the species' range, which spans from the north‐eastern to the southern USA (Doerder, 2019; Zufall, Dimond, & Doerder, 2013). However, the latitudinal variation in the origin of the 15 genotypes used in this study is not big enough to allow formal testing for such an effect.…”

Documentation of a new hypotrich species in the family Amphisiellidae, Lamtostyla gui n. sp. (Protista, Ciliophora) using a multidisciplinary approach

“…In order to verify the monophyly of Lamtostyla as well as many other genera of hypotrichs, additional molecular markers showing a higher evolutionary rate should be used, such as ITS or mitochondrial cytochrome oxidase subunit 1 (COI) gene. Indeed, in the genera where SSU rRNA presents similar features, like Tetrahymena Furgason, 1940 and Paramecium Müller, 1773, these additional markers are routinely characterized and used for fast identification [81][82][83][84][85][86] . Additionally, the combined phylogenetic analyses of multiple genes (e. g., SSU rRNA, ITS1-5.8S-ITS2 and LSU rRNA or phylogenomic data) with increased sampling are now becoming popular within ciliates [87][88][89][90][91] , also in the Hypotrichia 31,32,34,35,38 , to study the evolutionary relationships, and are revealing to provide more robust interpretations.…”