Competition definitely plays a role in community structure, but how much and are these effects homogeneous? Gurevitch concludes that at all trophic levels are subject to competition however they are effected at different levels. Carnivorous and deposit feeders and primary producers all have a mean effect size of below 0.4 demonstrating that their is a low level response, whereas filter feeders and herbivores were show to have >1.0 mean effect size demonstrating a large response. However, it is interesting to note that although Filter Feeders and Herbivores were shown to respond to competition stronger most of the studies were done on these trophic categories. This may be bias, or it may be that studies looking at competition in Carnivores, deposit feeders and primary producers have not shown publishable results. So, the take home message is competition plays a role, but the extent of its role is dependent upon trohpic level.
Who is the better competitor?
http://mozey.files.wordpress.com/2007/10/112lion.jpg
Sunday, February 28, 2010
Friday, February 19, 2010
Further Thoughts on “Which has a Stronger Impact on Community Structure?” Time?
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?
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?
Saturday, February 13, 2010
Seed mimicry in plants
The kind of mimicry I mentioned yesterday, with weeds growing to look like crops, is called Vavilovian mimicry; the wikipedia article has a couple of neat examples. A brief paper on this, which is still apparently one of the longer treatments, is Barrett, S. (1983) Crop Mimicry in Weeds. Economic Botany. 37:255–282. There's a horrible scanned pdf of it available here.
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