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Research Article

How Many Species Are There on Earth and in the Ocean?

  • Camilo Mora mail,

    moracamilo@hotmail.com

    Affiliations: Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada, Department of Geography, University of Hawaii, Honolulu, Hawaii, United States of America

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  • Derek P. Tittensor,

    Affiliations: Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada, United Nations Environment Programme World Conservation Monitoring Centre, Cambridge, United Kingdom, Microsoft Research, Cambridge, United Kingdom

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  • Sina Adl,

    Affiliation: Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada

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  • Alastair G. B. Simpson,

    Affiliation: Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada

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  • Boris Worm

    Affiliation: Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada

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  • Published: August 23, 2011
  • DOI: 10.1371/journal.pbio.1001127
  • Featured in PLOS Collections

Reader Comments (9)

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Are Nematoda/Nemata really HYPOdiverse?

Posted by markb1 on 02 Sep 2011 at 14:29 GMT

In this interesting analysis, I was struck that the 'count' for the phylum Nematoda/Nemata was apparently (through interpretation of figure 2) rather low number of taxa. indeed, Figure 3 suggests that Nematoda/Nemata have more described species than would be predicted from the predictions arising from modeling of their higher taxa. While the sub-kingdom breakdown of estimates per phylum is not given, it would thus seem that Nematoda/Nemata are predicted to have somenting like 25,000 species worldwide.
This contrasts with analyses performed through intensive morphological and molecular sampling of meiofauna across defined sites, where specimen number (nematodes are ~75% of all meiofauna), species richnesses (hundreds of taxa in the surveys, with many unique per site) and taxonomic deficit (most specimens are not classified or classifiable to known taxa) together suggest global species counts in the high hundreds of thousands to many millions (see Lambshead, J. Oceanis 19, 5-24 (1993); Lambshead, P. J. D. & Boucher, G. J. Biogeogr. 30, 475−485 (2003); Creer et al. Molecular Ecology 19 s1, 4–20 (2010)). Similarly, cryptic taxa within named species may be very, very common: focused analyses on 'widespread' species have revealed them to be complexes of many taxa (e.g. "Rhabditis marina", a common littoral species of Atlantic and North Sea coasts of the central belt of Europe, may comprise tens of sister species; Derycke et al. Zoological Journ Linn Soc 152, 1–15 (2008))
This raises the question as to whether these meiofaunal animals (and indeed all hyperabundant meiofauna) obey the same rules as the bulk of the animals: perhaps taxonomic neglect, systematic conservatism and hyperdiversity means that even modelling cannot recover true diversity?

No competing interests declared.