L'adaptació de nínxol va promoure la diversificació evolutiva del depredadors petits del oceà

10 pages, 5 figures, supporting information https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2020955118/-/DCSupplemental.-- Data Availability: DNA sequences and metadata from the Malaspina expedition are publicly available at the European Nucleotide Archive (ENA; https://www.ebi.ac.uk/ena; accession numbers PRJEB23913 (66) [18S rRNA genes] and PRJEB25224 (68) [16S rRNA genes]). DNA sequences from Tara Oceans are also stored at ENA with the accession numbers PRJEB6603 (76) for the SAGs, PRJEB6609 (101) for the metatranscriptomes, and PRJEB4352 (100) for the metagenomes (reference Datasets S1 and S4). Genome coassemblies, coding sequence predictions, and amino acid predictions have been deposited in FigShare (DOI: 10.6084/m9.figshare.13072322) (89). All other study data are included in the article and/or supporting information
Unicellular eukaryotic predators play a crucial role in the functioning of the ocean ecosystem by recycling nutrients and energy that are channeled to upper trophic levels. Traditionally, these evolutionarily diverse organisms have been combined into a single functional group (heterotrophic flagellates), overlooking their organismal differences. Here, we investigated four evolutionarily related species belonging to one cosmopolitan group of uncultured marine picoeukaryotic predators: marine stramenopiles (MAST)-4 (species A, B, C, and E). Co-occurrence and distribution analyses in the global surface ocean indicated contrasting patterns in MAST-4A and C, suggesting adaptation to different temperatures. We then investigated whether these spatial distribution patterns were mirrored by MAST-4 genomic content using single-cell genomics. Analyses of 69 single cells recovered 66 to 83% of the MAST-4A/B/C/E genomes, which displayed substantial interspecies divergence. MAST-4 genomes were similar in terms of broad gene functional categories, but they differed in enzymes of ecological relevance, such as glycoside hydrolases (GHs), which are part of the food degradation machinery in MAST-4. Interestingly, MAST-4 species featuring a similar GH composition (A and C) coexcluded each other in the surface global ocean, while species with a different set of GHs (B and C) appeared to be able to coexist, suggesting further niche diversification associated with prey digestion. We propose that differential niche adaptation to temperature and prey type has promoted adaptive evolutionary diversification in MAST-4. We show that minute ocean predators from the same phylogenetic group may have different biogeography and genomic content, which needs to be accounted for to better comprehend marine food webs
F.L. was supported by the Spanish National Program Formación de Personal Investigador 2016 (BES-2016-076317, Ministerio de Ciencia e Innovación, Spain). R.L. was supported by a Ramón y Cajal fellowship (RYC-2013-12554, Ministerio de Economía y Empresa, Spain). This work was supported by the projects INTERACTOMICS (Unveiling Core Ecological Interactions in Marine Microbial Communities Using Omics Approaches) (CTM2015-69936-P, MINECO, Spain, to R.L.), MicroEcoSystems (240904, Research Council of Norway, to R.L.), and MINIME (Microbial Evolution and Population Genomics in a Changing Ocean) (PID2019-105775RB-I00, Agencia Estatal de Investigación Spain, to R.L.). I.M.D. and A.L. were supported by the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie Grant Agreement No. 675752 (SINGEK [Promoting Single Cell Genomics to Explore the Ecology and Evolution of Hidden Microeukaryotes]: http://www.singek.eu). We thank the Consejo Superior de Investigaciones Científicas (CSIC) Open Access Publication Support Initiative through the Unit of Information Resources for Research for helping to cover publication fees
With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)