The field of ecology focuses on interactions between organisms and between organisms and their environment. This includes an explicit focus on a large variety of different ways that species interact with one another. Such interactions form the basis of a key question in ecology, namely, what is found where and why? Species can have positive, neutral or negative effects on each other. The most famous ecological interactions are those of predation and competition. In plant ecology, we often invoke competition as the key driver of interactions between species that require the same essential resources.