Gilbert & Parker University of California-Berkeley & -Santa Cruz DEB - 9806517 & 9808501 A central question in the ecology of invading organisms involves why some introduced plant species fail to succeed in a habitat while others become noxious invaders with high populations. Two competing theories have been posed to answer this question focusing on the role of natural enemies in regulating the population dynamics of invading plant species. The natural enemies hypothesis, the foundation for classical biological control programs, proposes that successful invaders leave behind the pests and pathogens that control them in their home habitats. The biotic resistance hypothesis suggests that most invading organisms are the successful targets of natural herbivores and pathogens and that successful invasions are the exception to the usual run of things. This project will test these two hypotheses using clover and burclover as a model system. It will examine plant-pathogen interactions using a combination of field and greenhouse experiments to compare native vs. exotic clovers in trying to sort through situations in different locations. It will test the prediction that disease resistance should be more prevalent in native hosts - consistent with the biotic resistance hypothesis.
