Refugium (population biology)

In biology a refugium (plural: refugia) is a location of an isolated or relict population of a once widespread animal or plant species.

This isolation (allopatry) can be due to climatic changes or human activities such as deforestation and over-hunting. Present examples of refuge species are the mountain gorilla, isolated to specific mountains in central Africa, and the Australian Sea Lion, isolated to specific breeding beaches in South Australia due to over hunting. This isolation, in many cases, can be seen as only a temporary state; however, some refugia may be long-standing, thereby having many endemic species, not found elsewhere, which survive as relict populations.

Some ancestral human populations may have been forced back to similar small isolated pockets in the face of the continental ice sheets during the last ice age. Suggested examples include the Bering land bridge, Ukrainian LGM refuge and the Iberian peninsula.

Speciation
Jürgen Haffer first proposed the concept of refugia to explain the biological diversity of bird populations in the Amazonian river basin. Haffer suggested that climatic change in the late Pleistocene led to reduced reservoirs of habitable forests in which populations become allopatric. Over time, this led to speciation, that is, populations of the same species different refugia evolved differently, creating parapatric sister species. As the Pleistocene ended, the arid conditions gave way to the present humid rainforest environment, reconnecting the refugia.

This mode of speciation has since been expanded and been used to explain population patterns in other areas of the world, such as Africa and North America. Theoretically, current biogeographical patterns can be used to infer past refugia: where several unrelated species follow concurrent range patterns, the area may have been a refugium. But this model of speciation is still highly controversial.

Drug resistance refugia
Refugia is the proportion of the population that is not selected by drug treatment.

-"In refuge" from drug

It provides a pool of suspectible genes. It dilutes resistant genes in the population. Until recently, overlooked as the most important component of drug resistance selection.