I thought some of you may like to see a presentation I did last semester on this very subject in an ecology class. It has some relevant links, and a few nice graphics. You can follow the refernces as well.
http://docs.google.com/Presentation?id=dfrz479d_1xkjbs4cj
http://docs.google.com/Presentation?id=dfrz479d_1xkjbs4cj