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Re: Dino farts

I have seen some phylogenies where Archaea is the sister group to Eukaryota, others where Eubacteria is the sister group to Eukaryota, and others where there is a trichotomy between the three groups. However, I think the latter is most often a byproduct of using ranks, i.e. each is a Domain so they must be equal. Not sure which of the first two phylogenies is the best supported but there are characters supporting each arrangement and my guess would be that there is a nested sister group phylogeny rather than a trichotomy. 

Dan




On 5/7/2012 8:55 PM, Tim Williams wrote:

Dann Pigdon<dannj@alphalink.com.au>  wrote:



Surely in order to determine the amount of methane sauropods produced globally, 
we'd need to
know:

- Whether or not they utilised methanogenic bacteria (not all modern herbivores 
do).


The authors used non-ruminant herbivores to derive their estimates.


BTW, a pedantic but important correction: methanogenic microbes are
archaea, not bacteria.  Archaea are the so-called Third Domain of Life
(after Bacteria and Eukaryota).  Phylogenetically speaking, archaea
are no more closely related to bacteria than we are.



- The total biomass of sauropods in the world at any one time.
- The rate at which digestion took place.

Pinning any of these factors down with any degree of accuracy would seem to be 
a tall order.


The authors do show their working.  Although there are certainly a lot
of assumptions made along the way.


As you imply, the range of methane production among herbivorous
mammals is highly variable.  For example, herbivorous marsupials
produce far less methane than ruminants, in part because of the
different anatomies of their respective digestive systems, and in part
because of the microbes themselves (lower numbers of methanogenic
archaea in marsupials, plus different metabolic interactions with
fermentative bacteria).




I'm also puzzled as to why the amount of methane estimated to have been 
released by sauropods
compared to the amount estimated for modern domestic livestock is of any 
statistical importance.
There are more herbivores currently in the world than just human livestock.


Yes, but ruminants (including livestock) are notoriously high emitters
of methane.






Cheers

Tim



I'm also puzzled as to why the amount of methane estimated to have been 
released by sauropods
compared to the amount estimated for modern domestic livestock is of any 
statistical importance.
There are more herbivores currently in the world than just human livestock.

And even if sauropods did produce that much methane, wouldn't decomposing plant 
matter still
produce similar amounts whether it got eaten by herbivores or not?

--
_____________________________________________________________

Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
_____________________________________________________________




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