The epochal steady state

In Chapter 3, we saw that diversity may often – or even usually – wobble around a steady state for millions of years. How can we explain that? We should be able to deduce a theory to do the job. At such long time scales, that theory must center on rates of speciation and extinction.

Many factors influence speciation and extinction rates. But only negative feedback variables can produce a steady state. Recall (Chapter 8) that in negative feedback, a product depresses its own rate of production. Without negative feedback, diversity would go out of control. It would crash to zero or skyrocket to infinity. Thus, we must figure out how higher diversities reduce the rate of change of diversity.

As in all ecological considerations, feedback variables exist because the world is finite. Space is limited. Energy flow is limited. Time is limited. Physics hems life in from all sides. How do these limits translate into diversity's steady states? I begin by considering diversity within one trophic level. Then I show how the steady state changes when other levels get added.

The steady state within one trophic level

Geographical speciation within a trophic level Species restrict each other's niche breadths.