20 November 2008

B0006459 A diatom frustulePhoto Annie Cavanaugh – Wellcome Images Creative Commons 2.0

2Diatoms are dynamite.  They are also deeply rad and, one might say, totally protarded.  As a person interested in the evolutionary trajectory of marine ecosystems I follow the diatom evolution beat with great zeal.  So I was excited to see this paper pop up in Nature last week.

It’s an interesting paper, documenting exceptionally high rates of genomic evolution among diatoms and pervasive lateral gene transfer from bacteria to the diatom genome, though I must admit that many of the genetic details are above my head.  Once sentence (or rather, parenthetical clause) gave me pause however:

The more rapid evolutionary rates of diatoms compared with other organismal groups (for example, the fish–mammal divergence probably occurred in the Proterozoic era earlier than 550 Myr ago) is consistent with previous observations — Bowler and friends (2008)

Uh is it just me, or is that a, er, liberal estimate?  The authors cite the Clinton-era classic: Kumar and Hedges 1998 for that divergence date.  (You might remember the film adaptation, Kumar and Hedges go to HOVERGEN, where Neil Patrick Harris goes crazy and snorts coke off the electrophoresis tray).

Rereading that paper, it seems that the Bowler and co. are referring to the proposed timing of the Homo/hagfish split. The date they are looking for–the split between sarcopterygians (e.g. Homo) and actinopterygians (e.g. Takifugu)–is probably more like 450 Ma, at least based on Kumar and Hedges (1998), that date may have been updated since then I don’t know.  100 million years might seem like a trivial matter, but you know, 100 million years here or there, and pretty soon you’re talking about real time.  In this case, the disparity in genomic evolutionary rates between vertebrates and diatoms is reduced somewhat relative to what the authors report, although their overall point that centric and pennate diatoms have experienced relatively rapid genomic divergence over the past 90 Ma or so holds.

One wonders how a mistake like that (albeit not one of tremendous importance to the central thrust of the paper) slipped past all sexillion authors (seriously, check out the author list), the reviewers and the Nature editorial staff.

Whatever, diatoms are still totally toothpaste bro.


Bowler et. EVERYONE (2008) The Phaeodactylum genome reveals the evolutionary history of diatom genomes, Nature 456:13 doi:10.1038/nature07410.

Kumar and Hedges (1998) A molecular timescale for vertebrate evolution, Nature 392:30 doi:10.1038/31927

4 Responses to “Wha?”

  1. Jeremy Says:

    you tell some jokes

  2. Neil Says:

    There’s no joking in microecos

  3. 220mya Says:

    Not to mention the devastating criticism of the Kumar & Hedges paper:

    Graur, D., and W. Martin. 2004. Reading the entrails of chickens:
    molecular timescales of evolution and the illusion of precision.
    Trends in Genetics 20:80–86.

  4. Neil Says:

    Oh yeah, the sequel–Kumar and Hedges Escape from the 13.8 Billion year 95% Confidence Interval.

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