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Ecological niche partitioning in the picoplanktonic green alga Micromonas pusilla: evidence from environmental surveys using phylogenetic probes

Authors

  • Elodie Foulon,

    1. Station Biologique, UMR 7144 Centre National de la Recherche Scientifique, Institut National des Sciences de l'Univers et Université Pierre et Marie Curie (Paris 6), Place George Teissier, 29680 Roscoff, France.
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  • Fabrice Not,

    1. Station Biologique, UMR 7144 Centre National de la Recherche Scientifique, Institut National des Sciences de l'Univers et Université Pierre et Marie Curie (Paris 6), Place George Teissier, 29680 Roscoff, France.
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  • Fabienne Jalabert,

    1. Station Biologique, UMR 7144 Centre National de la Recherche Scientifique, Institut National des Sciences de l'Univers et Université Pierre et Marie Curie (Paris 6), Place George Teissier, 29680 Roscoff, France.
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  • Thierry Cariou,

    1. Station Biologique, UMR 7144 Centre National de la Recherche Scientifique, Institut National des Sciences de l'Univers et Université Pierre et Marie Curie (Paris 6), Place George Teissier, 29680 Roscoff, France.
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  • Ramon Massana,

    1. Department of Marine Biology and Oceanography, Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta 37–49, 08003 Barcelona, Catalonia, Spain.
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  • Nathalie Simon

    Corresponding author
    1. Station Biologique, UMR 7144 Centre National de la Recherche Scientifique, Institut National des Sciences de l'Univers et Université Pierre et Marie Curie (Paris 6), Place George Teissier, 29680 Roscoff, France.
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*E-mail simon@sb-roscoff.fr; Tel. (+33) 2 98 29 23 70; Fax (+33) 2 98 29 23 24.

Summary

Very few studies have analysed the niches of pelagic protist in details. This is because for most protists, both an accurate species definition and methods for routine detection and quantification of cells are lacking. The morphospecies Micromonas pusilla, a marine unicellular green alga, is the most ubiquitous and cosmopolitan picoeukaryote described to date. This species comprises several independent genetic lineages or clades, which are not currently distinguishable based on comparison of their morphology or biogeographical distribution. Molecular probes were used to detect and quantify the genetic clades of M. pusilla in samples from temperate, polar and tropical environments in order to assess potential ecological niche partitioning. The three clades were detected in all biogeographical regions studied and were commonly found in sympatry. Cell abundances recorded for clades A and B were high, especially at coastal stations. Clade C, when detected, was always at low abundances and is suggested to be a low-light clade. Shifts in the contribution of clades to total M. pusilla abundance were observed along environmental gradients, both at local and basin-wide scales. This suggests that the phylogenetic clades occupy specific niches and confirms the existence of cryptic species within the morphospecies M. pusilla. Parameters which can precisely explain the distribution of these cryptic species remain to be elucidated.

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