A little off the beaten track for HN, but a classic paper in ecology that introduced the idea of trophic cascades:<p>Hairston, Smith and Slobodkin.  1960.  Community structure, population control, and competition.  American Naturalist 94: 421-425.<p>see <a href="http://en.wikipedia.org/wiki/Trophic_cascade" rel="nofollow">http://en.wikipedia.org/wiki/Trophic_cascade</a> for more information