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One trillion “species” on Earth?

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From ScienceDaily:

Earth could contain nearly 1 trillion species, with only one-thousandth of 1 percent now identified, according to a study from biologists. The estimate is based on the intersection of large datasets and universal scaling laws.

Scaling laws, like those discovered by the IU scientists, are known to accurately predict species numbers for plant and animal communities. For example, the number of species scales with the area of a landscape.

“Until now, we haven’t known whether aspects of biodiversity scale with something as simple as the abundance of organisms,” Locey said. “As it turns out, the relationships are not only simple but powerful, resulting in the estimate of upwards of 1 trillion species.”

The study’s results also suggest that actually identifying every microbial species on Earth is an almost unimaginably huge challenge. To put the task in perspective, the Earth Microbiome Project — a global multidisciplinary project to identify microscope organisms — has so far cataloged less than 10 million species.

“Of those cataloged species, only about 10,000 have ever been grown in a lab, and fewer than 100,000 have classified sequences,” Lennon said. “Our results show that this leaves 100,000 times more microorganisms awaiting discovery — and 100 million to be fully explored. Microbial biodiversity, it appears, is greater than ever imagined.” More. Paper. (paywall) – Kenneth J. Loceya, and Jay T. Lennona. Scaling laws predict global microbial diversity. PNAS, 2016 DOI: 10.1073/pnas.1521291113


Ecological scaling laws are intensively studied for their predictive power and universal nature but often fail to unify biodiversity across domains of life. Using a global-scale compilation of microbial and macrobial data, we uncover relationships of commonness and rarity that scale with abundance at similar rates for microorganisms and macroscopic plants and animals. We then show a unified scaling law that predicts the abundance of dominant species across 30 orders of magnitude to the scale of all microorganisms on Earth. Using this scaling law combined with the lognormal model of biodiversity, we predict that Earth is home to as many as 1 trillion (1012) microbial species.

Now would be a nice time to know what a ”species” even is No one can define it but it is the basis of Darwinian evolution.

And how does the “species” concept apply to microbes?

If numbers of species are said to be “undiscovered” or “declining,” don’t we need to start by agreeing on what we are talking about?

One hopes that the Royal Society and Templeton will make some time for that.

See also: Tree of Life online—with great graphics The tree of life is really better described as a river of life.

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8 Replies to “One trillion “species” on Earth?

  1. 1
    Mung says:

    Wow. There must then have been an unimaginably large number of species that have gone extinct then.

  2. 2
    Bob O'H says:

    It’s OK, Mung. Most of them were bacteria.

  3. 3
    Mung says:

    But didn’t we evolve from bacteria? Just think of all the intelligent species that could have been but were not to be.

  4. 4
    bornagain77 says:

    Semi Related:

    Rapid Evolution of Citrate Utilization by Escherichia coli by Direct Selection Requires citT and dctA. – Feb. 2016
    The isolation of aerobic citrate-utilizing Escherichia coli (Cit(+)) in long-term evolution experiments (LTEE) has been termed a rare, innovative, presumptive speciation event. We hypothesized that direct selection would rapidly yield the same class of E. coli Cit(+) mutants and follow the same genetic trajectory: potentiation, actualization, and refinement. This hypothesis was tested,,,
    Potentiation/actualization mutations occurred within as few as 12 generations, and refinement mutations occurred within 100 generations.,,,
    E. coli cannot use citrate aerobically. Long-term evolution experiments (LTEE) performed by Blount et al. (Z. D. Blount, J. E. Barrick, C. J. Davidson, and R. E. Lenski, Nature 489:513-518, 2012, http://dx.doi.org/10.1038/nature11514 ) found a single aerobic, citrate-utilizing E. coli strain after 33,000 generations (15 years). This was interpreted as a speciation event. Here we show why it probably was not a speciation event. Using similar media, 46 independent citrate-utilizing mutants were isolated in as few as 12 to 100 generations. Genomic DNA sequencing revealed an amplification of the citT and dctA loci and DNA rearrangements to capture a promoter to express CitT, aerobically. These are members of the same class of mutations identified by the LTEE. We conclude that the rarity of the LTEE mutant was an artifact of the experimental conditions and not a unique evolutionary event. No new genetic information (novel gene function) evolved.

  5. 5
    gpuccio says:


    Wow! That is really important news. 🙂

    Poor Lenski… All that time and effort just to make something so easy so difficult!

  6. 6
    Zachriel says:

    Mung: Just think of all the intelligent species that could have been but were not to be.


  7. 7
    Zachriel says:

    bornagain77: “We hypothesized that direct selection would rapidly yield the same class of E. coli Cit(+) mutants and follow the same genetic trajectory: potentiation, actualization, and refinement.

    The original experiment already tested that hypothesis, and showed that direct selection could result in Cit+ in a much shorter interval. However, the original experiment was not designed for direct selection of Cit+.

    bornagain77: “No new genetic information (novel gene function) evolved.

    That’s obviously not true. It’s not only new genetic information, it’s important genetic information to the bacteria.

    bornagain77: “This was interpreted as a speciation event.

    That’s false. Generally, speciation is not an event, but a process. Blount et al. asked “Will the Cit+ and Cit? lineages eventually become distinct species?” That clearly implies they are not yet separate species.

  8. 8
    bornagain77 says:

    Zach, only a dogmatist would try to defend the indefensible as you have done.

    Once again Mr. Arrington, I request that Zach be banned for being a troll.

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