Refers to the presence of and impact of organisms on the or of conspecifics.

With density dependence a can be regulated by environmental effects that have tend to have an impact on that varies as a function of population size.

Think of these things as indirectly impacting the or of organisms such as by making specific limiting or already even scarcer (). Alternatively, this can be due to or infectious disease to the extent that this can, for example, increase as a consequence of increases in population size ().

Note that density dependent can be viewed as the ecological equivalent to frequency-dependent selection. Indeed, frequency-dependent selection is explicitly natural selection that is density dependent. Contrast density independent.