Paul writes:
> But what case history examples can you cite that show the loss of the small stuff can have profound (e.g. "system failed") consequences?

You are correct, I don't have it. The whole subject is somewhat new and given to conjecture. It interests me, though. Maybe someone else can comment. 

* * *
Mace Vaughan, Xerces:

> Endangered species also can play a linchpin role in small, specialized systems, such as caves, oceanic islands, or some pollinator-plant relationships. For example, many plant species rely on one or a few pollinators. Decreased abundance or loss of any of these pollinators can have dramatic consequences, especially if a plant depends on a single, obligate pollinator.

* * *

Shahid Naeem, et al, in 1995

> From the limited literature available on the subject, four hypotheses summarize the possible general responses of ecosystems to declining species diversity. The first hypothesis, the 'redundant species' hypothesis, suggests that there is a minimum diversity necessary for ecosystem function but beyond that, most species are redundant in their roles (Lawton & Brown 1993). A second, contrasting view is the 'rivet' hypothesis which suggests that species are largely unique in their contribution to ecosystem performance (Ehrlich & Ehrlich 1981). This hypothesis likens species to the rivets holding together a complex machine and postulates that the function of an  ecosystem will be altered or impaired as its rivets (species) fall out.  A third view, the 'idiosyncratic response' hypothesis suggests that ecosystem processes change when diversity changes but that the response is unpredictable. Finally, the 'null' hypothesis is that ecosystem functions (i.e. processes) are insensitive to species deletions or additions (Vitousek & Hooper 1993).

Pete

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