Roger,
You are probably right and I am probably murdering the messenger, here.
For reasons having to do with the history of human evolution I probably
care about this issue a bit too much.
What makes for speciation is, I think, inhibition of migration. Obviously
it cannot be too great, that inhibition. There has been very little
speciation on the moon, so far as we know. There is a wonderful book
called Darwin's finches, by Lack, who describes speciation there as being
driven by a kind of ratchet effect in which once a species moved from one
island to another there would likely be a time before anotehr member of its
kind would appear to compete with it.
the impediment need not, of course, be a body of water It can be a wide
river or a deep mountain valley, Madagascar has all three.
It may also have a variable climate, but my assertion, right or wrong, is
that a variable climate opposes speciation because variants keep getting
trimmed off. Benthic habitats ... which are impoverished in total biomass
but very stable.... are surprizingly speciose . I would bet that as
climates go .... compared to newfou ndland, for instance,.... Madagascar is
pretty stable. .
I am on a phone line here in MA so looking this stuff up is a pain, but we
can go to a coffee house with wifi and answer all this stuff when I get
back, which wont be too long now.
Nick
I can't tell whether you're worried that I'm misrepresenting the findings of
the paper or that the authors are ignorant of island biogeography.
I said: "The second, which was published a day earlier, is about the same
thing, only for real. The environment in Madagascar is diverse, but the
diverse regions all share an unpredictable rainfall through the year and
year to year. This unpredictability is proposed to contribute to the
unusual diversity of mammals found."
Maybe diversity is the wrong word. It isn't the one the authors chose in
their abstract. The issue is the extreme spread of life cycle adaptation
among the mammals found.
-- rec --
On 8/15/07, Nicholas Thompson <nickthompson at earthlink.net> wrote:
>
> Roger,
>
> Is it possible w e are confusing two variables here? Variability in the
> environment and isolation of the environment from others.
>
> Galapagos Islands have both a high level of endemicity and many missing
> taxa, no? So, Madagascar is just a rather extreme example of island
> geography?
>
> Nick
>
>
Locked
