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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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Bacterial/Archaeal species richness

Posted by pschloss on 25 Aug 2011 at 20:41 GMT

The authors understate how poor the estimates of bacterial and archaeal richness are.

First, there are entire phyla of both kingdoms that lack any cultured representatives. For example, the Acidobacteria typically represent 15-30% of bacteria in soil; however, we only have a handful of cultured representatives of this phyla and even fewer have valid names. Imagine a Martian looking down on Earth and saying, "We know there's this thing that we'll call Plantae. It's really abundant, but we don't know what it does because we can't grow it in culture." That's what bacteriologists are dealing with.

Second, 16S rRNA gene surveys of insects has basically revealed new bacterial species in each insect. It would seem reasonable to expect bacterial diversity to be larger than insect diversity and the other metazoa as well.

Finally, as is mentioned we have a rather poor definition of what constitutes a bacterial or archaeal species. Regardless the arguement by most is that we are too general in defining species. Needless to say this would only increase the relative number of bacterial/archaeal species to the number of the more charismatic megafauna.

No competing interests declared.