The lynx populations peak slightly after the hares. However, despite the obvious correlation, it's now known that winter food shortage causes the decline in hare numbers, not the influence of the predator. Predator - herbivore relationships are similar, but plants are usually damaged, not killed. All the above effects are major selective forces as they reduce distribution and abundance of prey species, and possibly predators as well. Many appear to have general protein binding activity or disrupt membrane structure.
Examples are tannins - widely distributed in leaves, stems, fruits, bark , and wood of plants.
The importance of interference competition by release of toxic compounds into the surroundings by plants has been debated by ecologists. Part of the argument results from the difficulty in separating the components of interference and scramble competition in field situations. Recent developments in this area suggest that this can be done. Allelopathy is most recognizable in areas with chaparral or Mediterranean climate, deserts, and other important special habitats. The other plant in the relationship often suffers reduction of fitness.