Re: Life's complexity: self-organization, evolution or both?

Perplexed in Peoria wrote:

"John Harshman" <jharshman.diespamdie@xxxxxxxxxxx> wrote in message news:u8jIi.621$6p6.331@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Bill Morse wrote:

Now obviously the change is due to "the ability of different organisms to
outcompete others in particular environments." But in some of these
communities, the interactions between different organisms, the individuals
helping "create each others' environments", becomes a tight enough loop
that the whole community does behave in some sense as a superorganism.

I can't think of any such communities. There are tight interactions, but
they tend to be between species pairs at the most. And the cases in
which species pairs are always found together, never separately, are
surprisingly few. Even if species A depends absolutely on species B in
some locality, it may depend on species C in some other locality.


I'm not sure that the crucial interactions involved here are 'loops'. In
the cases that Bill mentions in which there seems to be a sharp and
complete change in the member species in the community, I suspect that
it is due to a change in the single primary-producer species.

No, it seems to be due more to a sharp environmental gradient. His
primary example is a forest right next to the ocean, fer chrissake. you
don't need any tight species interactions to explain that one.

There may
well be loops at the higher trophic levels, but I suspect that most
communities are supported by a single Ayn Rand style rugged individualist
species which is beholden to no other species but is directly or indirectly
grazed and parasitized by everyone else.

I can think of very few examples for which this is true. Kelp forests,
perhaps? I really don't know how much kelp species vary geographically,
but my naive expectation is that substituting a diferent species of kelp
would not change the species composition much.

Change the identity of that
key primary producer, and the identities of every other player perforce
must change too.

I doubt it. In most communities there are a variety of primary
producers. Now there is some talk in ecology about "keystone species",
which can be plants or animals. I haven't kept up with the literature on
that, and perhaps I would be surprised. But these are local phenomena.
It seems to me there are more likely to be keystone roles, capable of
being performed by different species in different places. And I don't
think there is anything there to support the notion of communities as
"superorganisms".

.

Relevant Pages

  • Re: Lifes complexity: self-organization, evolution or both?
    ... communities, the interactions between different organisms, the individuals ... I can't think of any such communities. ... they tend to be between species pairs at the most. ... physical environment. ...
    (talk.origins)
  • Re: Lifes complexity: self-organization, evolution or both?
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    (talk.origins)
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