When are Two Phenological Patterns Different?

The importance of the timing of certain events, such as flowering, germination of seeds, bud break, and dispersal, in the lives of many species has long been recognized. In many cases, the phenological patterns of these events have evolved by natural selection. In some cases, we can formulate hypotheses of adaptation concerning phenological patterns. These hypotheses can be tested by observing phenologies only if there is some valid method for determining whether two phenological patterns are different. This paper describes such a method and presents three natural examples of its use.