Realized stickleback niche if gill parasite is present. H1. Gills damaged so cant osmoregulate as well H2. Sufficient resource Tolerable conditions Dispersal limitation? Enemies? Definitions: Relict population: Residual population left over from time when environment Sequoia could support its survival and redwoods reproduction, which can no longer replace itself locally Sink habitat: Habitat where death rates exceed birth rates, and organisms are present only because of immigration from Source Habitats (where births exceed deaths) Grazing hot spot? Subsidies Sinks Relicts?