Learning Objectives

15.3.1 Explain the consequences of positive interactions on the distribution and abundance of species.

15.3.2 Describe how positive interactions can increase species diversity in communities.

15.3.3 Illustrate ways in which positive interactions can affect ecosystem processes.

So far in this chapter, we've considered features that are common to commensalism and mutualism as well as characteristics that are unique to mutualism. At various points, we've mentioned some ecological consequences of positive interactions, including increased survival rates and the provision of food and habitat. In this section, we'll take a closer look at how positive interactions affect populations of organisms and the communities in which they are found.