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Re: Shaking up the bird family tree



On Fri, Jun 27, 2008 at 5:08 AM, Jaime A. Headden <qilongia@yahoo.com> wrote:
>
>  The problem here is that to argue that flight is lost, you must have 1) a 
> single gaining of flight, 2) loss of flight in ostriches, 3) loss of flight 
> in rheas, and 4) loss of flight in the cassowary/kiwi/emu clade. This is more 
> steps than a simpler explanation in which tinamous gained flight after the 
> whole lost it. A tad more parsimonious, rather.

Given some other character, sure. How many times has powered flight
been lost in _Avialae_? I'm thinking at least 11, probably more (not
even counting multiple losses among palaeognathes). How many times has
powered flight evolved in all of _Amniota_ (or _Deuterostomia_, for
that matter)? Putting aside the question of secondary tinamid volancy,
exactly 3. So, in this area of the Tree of Life, loss of flight is
over three times more likely than gaining of flight (perhaps well
over).

Look at ecdysozoans as well: flight gained once (_Insecta_), lost ...
at least 8 times that I can think of, and probably a lot more. (And
even more if you count sexually dimorphic loss of flight, as in
strepsipterans.)

On another note, I have a question: are the long branches of tinamous
due in part to shorter generation times? (This isn't relevant to the
topology or the character distribution -- just curious. And do they
even have shorter generation times?)
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