The term allochrony is used in ecology to describe a situation where two biological entities (typically species) occur in the same area, and are thus sympatric, but are never or rarely active simultaneously. The most common temporal scale at which this is seen is seasonal, and greater emphasis is placed on the phenomenon when the two entities share a common resource for which they would otherwise be in competition (for example, feeding on the same host plant, or consuming the same prey).
Allochrony is one of the few ecological phenomena that lend clear support to models and theories of sympatric speciation; the idea that related lineages can differentiate into independent gene pools while still sharing the same physical environment, simply by virtue of changes in the life cycle that lead to separation in time of different portions of the ancestral population.