families

[Curtis Clark]

At 08:27 AM 3/3/99 -0500, Hugh Wilson wrote:
> The Asteraceae has, for
>instance, had a significant global phylogenetic impact; as indicated
>by its current diversity and distribution.

This whole issue easily falls apart though imprecise terminology. What is
"phylogenetic impact"? Certainly Asteraceae are important members of many
plant communities, and since the family is also a clade, perhaps that means
something. Perhaps there is a shared apomorphy that causes the tiny annual
Eriophyllum wallacei of the Mojave Desert, the tree-sized Montanoas of
Mexico, and the Hawai`ian silverswords to all be successful. If that
apomorphy could be discovered, the clade that it diagnosed (whether a
family or some other rank, or even unnamed) could be said to have
ecological importance. But there are a lot of steps between the
speculation, the hypothesis, and the confirmation.

The "units of selection" question is a separate, but perhaps related,
issue. I think a good point can be made that if one clade has a higher rate
of speciation or a lower rate of extinction than another, the first clade
will increase relative to the second. What that means in terms of
interactions between individuals of those clades in a specific habitat is
anybody's guess.


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