Hello blog!!!!
So I suppose this makes me one of those terrible persons who lays awake on a Friday night reflecting on a community ecology class instead of… well, what do most twenty-somethings in the Bronx do on a Friday night?
I am trying, however, to (a) get my head around and (b) figure out if I agree with something Mr… well let’s call him Bob… said in class on Thursday (the 18th) towards the end of our discussion on “which has a stronger impact on community structure (and evolution): competition or predation?” His comment, as I understood it, was that time was a bigger/underlying driving force, and competition and predation would both be happening and contributing to changes in various populations anyways, but not driving evolution or community structure per sey. The examples supporting this idea included a sort of island biogeography colonization type thing, with it taking time for more and more species to arrive on an island, and alter the dynamic of the community, and also comparing the tropics to temperate forests, and a notion that the tropics are more diverse and dynamic and the critters in the tropics are more specialized (within a very specific niche) and eccentric and extreme because they have been available to colonize and evolve and specialize for longer time periods than temperate areas, which were covered in thick sheets of ice in geologically recent times.
Interesting idea, which seems to be supported by those examples, but when I think of the idea in a different frame of mind, it does not work out so well. Thinking of a typical, modern, successional cycle in temperate North America, and thinking more of plants and animals you can see without a magnifying glass (I know, what a terrible thing for an ecologist to do), a climax(ish) stage is not typically the most diverse (or species rich for that matter) or even the most specialized in terms of niche availability and use. Little or no edge habitats, reduced understory dynamic, etc etc etc.
So, does the idea that time is the biggest underlying driving force in community structure and dynamic only work with the unique (specific and simplified) parameters of island biogeography (colonization) and the big question of why the tropics are so much richer and more diverse than temperate climates? Or is there something about how I am framing my example and understanding (with climax communities within temperate regions only) that makes it unamenable to ‘Bob’s’ idea?
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Nice post... Who wrote it?
ReplyDeleteBut.. anyway, if I remember correctly... We concluded that disturbances not specifically time was the 3rd mechanism driving community structure. This, disturbance, was what Kevin ended up writing on the power-point.
To use your example, in terrestrial uplands or forests dominated by a climax species, yes there is lower species richness, but if a disturbance, say a fire created by lightning occurred or something like chestnut blight, we might see a reorganization of community structure and maybe an increase in richness.
In the new community structure predation and competition might be the driving mechanisms in the succession of this disturbed area, however these mechanisms were catalyzed by the disturbance.
J