The community composition of any group of organisms should theoretically be determined by a combination of assembly processes including resource partitioning, competition, environmental filtering, and phylogenetic legacy. Environmental DNA studies have revealed a huge diversity of protists in all environments, raising questions about the ecological significance of such diversity and the degree to which they obey to the same rules as macroscopic organisms. The fast-growing cultivable protist species on which hypotheses are usually experimentally tested represent only a minority of the protist diversity. Addressing these questions for the lesser known majority can only be inferred through observational studies. We conducted an environmental DNA survey of the genus Nebela, a group of closely related testate (shelled) amoeba species, in different habitats within Sphagnum-dominated peatlands. Identification based on the mitochondrial cytochrome c oxidase 1 gene, allowed species-level resolution as well as phylogenetic reconstruction. Community composition varied strongly across habitats and associated environmental gradients. Species showed little overlap in their realized niche, suggesting resource partitioning, and a strong influence of environmental filtering driving community composition. Furthermore, phylogenetic clustering was observed in the most nitrogen-poor samples, supporting phylogenetic inheritance of adaptations in the group of N. guttata. This study showed that the studied free-living unicellular eukaryotes follow to community assembly rules similar to those known to determine plant and animal communities; the same may be true for much of the huge functional and taxonomic diversity of protists.

Laboratory of Soil Biodiversity Institute of Biology University of Neuchâtel Rue Emile Argand 11 CH 2000 Neuchâtel Switzerland

Laboratory of Soil Biodiversity Institute of Biology University of Neuchâtel Rue Emile Argand 11 CH 2000 Neuchâtel Switzerland Department of Zoology Institute of Biosciences University of São Paulo São Paulo 05508 Brazil Institute of Parasitology Biology Centre Czech Academy of Sciences Branisovska 31 České Budějovice 37005 Czech Republic

Laboratory of Soil Biodiversity Institute of Biology University of Neuchâtel Rue Emile Argand 11 CH 2000 Neuchâtel Switzerland Jardin Botanique de Neuchâtel Chemin du Perthuis du Sault 58 CH 2000 Neuchâtel Switzerland

Laboratory of Soil Biodiversity Institute of Biology University of Neuchâtel Rue Emile Argand 11 CH 2000 Neuchâtel Switzerland Laboratorio de Ecología Evolutiva y Filoinformática Departamento de Zoología Facultad de Ciencias Naturales y Oceanográficas Universidad de Concepción Barrio Universitario s n Casilla 160 C Concepción Chile Centro de Investigación en Recursos Naturales y Sustentabilidad Universidad Bernardo O'Higgins Avenida Viel 1497 Santiago Chile

Laboratory of Soil Biodiversity Institute of Biology University of Neuchâtel Rue Emile Argand 11 CH 2000 Neuchâtel Switzerland Microorganisms and Plants Group Department of Arctic and Marine Biology Faculty of Biosciences Fisheries and Economics University of Tromsø Framstredet 39 9037 Tromsø Norway

Laboratory of Soil Biodiversity Institute of Biology University of Neuchâtel Rue Emile Argand 11 CH 2000 Neuchâtel Switzerland Real Jardín Botánico CSIC Plaza Murillo 2 ES 28014 Madrid Spain

National Research Council of Italy Institute of Ecosystem Study 28922 Verbania Pallanza Italy

References provided by Crossref.org