Practice question

Metapopulation persistence depends on a dynamic balance between local extinction and colonization. When a patch population disappears, dispersers from occupied patches can establish a new local population, a process called recolonization. If recolonization rates are sufficient relative to extinction rates, the species can persist regionally even though no particular patch is occupied continuously. In the classic Levins model, the fraction of occupied patches changes as colonization creates new occupancy and extinction removes it. Dispersal is the movement mechanism that makes recolonization possible, but recolonization is the demographic event that directly counterbalances extinction of an already empty patch. This differs from the rescue effect, in which immigrants reduce the probability that a still-occupied local population will go extinct. Speciation and aggregation do not restore occupancy on the relevant ecological timescale. Patch isolation, matrix hostility, propagule supply, and habitat quality all influence recolonization success. Conservation corridors can therefore support regional persistence by allowing colonists to reach vacant suitable habitat, even when local environmental fluctuations continue to cause extinctions.