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The ciliophoran taxon Chonotrichia Wallengren, 1895 are epibionts typically on Crustacea. There are about 112 species reported from all around the world. These species are known essentially from microscopical observations, and molecular data are far from sufficient, which largely hinders the study on their phylogenetic relationships. Here, we present the complete small-subunit (SSU) rDNA sequences of three species from Roscoff, Brittany, France, and one from Switzerland. These sequences are used to analyze the phylogentic relationships of the Chonotrichia, covering all three controversial orders, Exogemmida Jankowski, 1972, Cryptogemmida Jankowski, 1975, and Chilodochonida Batisse, 1994, for the first time. The phylogenetic tree confirms that all chonotrich sequences group together, nested in the dysteriid sequences. The tree topology also shows the separation of the chilodochonids from Exogemmida, supporting the establishment of the order Chilodochonida. [ABSTRACT FROM AUTHOR]

Microbial planktonic communities are the basis of food webs in aquatic ecosystems since they contribute substantially to primary production and nutrient recycling. Network analyses of DNA metabarcoding data sets emerged as a powerful tool to untangle the complex ecological relationships among the key players in food webs. In this study, we evaluated co-occurrence networks constructed from time-series metabarcoding data sets (12 months, biweekly sampling) of protistan plankton communities in surface layers (epilimnion) and bottom waters (hypolimnion) of two temperate deep lakes, Lake Mondsee (Austria) and Lake Zurich (Switzerland). Lake Zurich plankton communities were less tightly connected, more fragmented and had a higher susceptibility to a species extinction scenario compared to Lake Mondsee communities. We interpret these results as a lower robustness of Lake Zurich protistan plankton to environmental stressors, especially stressors resulting from climate change. In all networks, the phylum Ciliophora contributed the highest number of nodes, among them several in key positions of the networks. Associations in ciliate-specific subnetworks resembled autecological species-specific traits that indicate adaptions to specific environmental conditions. We demonstrate the strength of co-occurrence network analyses to deepen our understanding of plankton community dynamics in lakes and indicate biotic relationships, which resulted in new hypotheses that may guide future research in climate-stressed ecosystems., (© 2020 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)