Friday, May 10, 2013

Ecological Meltdown in Predator-Free Forest Fragmentations


             For my community ecology class, we read a paper regarding the ecological meltdown of multiple predator-free islands created via a hydroelectric plant in Venezuela. No top predators reside here, as the islands are separated from the rest of the tropical forest surrounding them.  This has left only predators of invertebrates, seed predators, and herbivores.  The effects have been extremely noticeable and have begun to create completely different communities from the ones found on mainland close by.
            The lack of vertebrate predators has caused for the density of herbivores to skyrocket to 10-100 times greater than can be found in the mainland forests.  Due to this high number, it is believed that top predators are key in limiting herbivore populations on the mainland.  These herbivores have done extensive damage to the local populations of seedlings and saplings from the canopy trees.
            While these species are usually maintained via top-down regulation, the lack of species above them on the food chain has enabled their populations to grow at exponential rates.  This will most likely occur until they become restricted again, this time via bottom-up regulation.  Eventually, the populations will be so large that the amount of vegetation currently on the island won’t be enough to maintain them.  Depending on how rapid this transition is, it is possible that some of these species will undergo the bottleneck effect.  This can be devastating to a species, as it is usually accompanied by a large loss of genetic diversity.
            These island communities are completely circumstantial and don’t provide much information in terms of successional processes in the tropical rainforest.  That being said, they do provide an extremely interesting look at how the removal of any given species can cause widespread changes to an ecosystem.  It will also be interesting to see how the transition into bottom-up regulation takes place and whether it is as drastic as it has the potential to be.

paper:
http://www.uvm.edu/~ngotelli/Bio%20264/Terborgh.pdf

No comments:

Post a Comment