Re: Big Dinosaurs, Tiny Genomes

[Jeff Hecht <jeff@jeffhecht.com>]

Thanks for the references. Although I have not studied them in detail, I worry 
that their series of inferences may be taking them rather far out on a limb. I 
would have liked to see a statistical test of the hypothesis that cell size was 
related to organism size, something inferred from the larger genomes of 
flightless birds. Other tests that would be interesting to see are comparing 
predator vs. herbivore lines, both for the particular species and for the time 
the lineage had those traits. That would test the hypothesis that life style 
would select for genome size. Note that Oviraptor has an exceptionally large 
genome. The central question I'm addressing is the relative impact of ancestral 
traits and natural selection on genome size over 230 million years, and the 
data on flightless birds suggests natural selection is important.

By the way, there's a disconcerting howler at the very end of the Nature News 
piece: "An interesting next step would be to look at the genome sizes of the 
flying dinosaurs, the pterosaurs, which evolved flight independently of birds, 
says Organ." -- Jeff Hecht

At 10:03 PM -0800 3/7/07, Guy Leahy wrote:
>Here's more on the study:
>
>http://www.nature.com/nature/journal/v446/n7132/abs/nature05621.html
>
>http://www.nature.com/news/2007/070305/full/070305-6.html
>
>http://www.nature.com/nature/journal/v446/n7132/extref/nature05621-s1.pdf
>
>The supplementary data is very interesting.  The one
>sauropod in the sample (Apatosaurus sp.) appears to
>show a genome size which is intermediate to that of
>ornithischians.  Herrerasaurus exhibits an avian
>genome size, which might suggest this "avian" genome
>size thing goes back quite a ways within theropods
>(assuming that Herrerasaurus *is* a theropod.) 
>

-- 
Jeff Hecht, science & technology writer
jeff@jeffhecht.com  http://www.jeffhecht.com
525 Auburn St., Auburndale, MA 02466 USA
v. 617-965-3834; fax 617-332-4760