BSCI392
10-12-07
Trophic and community structure

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Communities:

Are they real? We are tempted to think of communities of organisms - either taxa or guilds of organisms that frequently co-occur and interact in the same environment - as parts of a coherent, machine-like mechanism (E.G.: African ratel and honey-guide). Maybe, or maybe they are present together coincidentally (Norway rat and black rat snake). With living ecosystems, we can at least chart the regular flow of energy through an environment as it passes through trophic levels from producers to primary consumers, secondary consumers, etc. E.G.: The trophic structure of the Galápagos Islands:

If we are uncertain about living communities, fossil communities are real trouble for three reasons:

>And yet, we can identify some communities with reasonable confidence and even begin to reconstruct their trophic structure when there are multiple stratigraphic and/or geographic recurrence of an association. Some analogous communities have formed multiple times in Earth history, with similar community structure but different taxonomic composition: reefs, for example.

Biological ghosts: Indeed, some extant communities only make sense if we consider their extinct members: