Disjunctive population

A disjunctive population, in ecology, is a colony of plants, animals, or other organisms whose geographic location is severed from the continuous range of the bulk of the species distribution. These populations may be severed from the continuous range due to physical barriers or habitat fragmentation. Some physical barriers may include a body of water, mountains, or other impassible terrain. In some cases a disjunctive population represents a relatively small outlier population from the main range, but in other cases, such as for the painted hunting dog, Lycaon pictus, the entire population is scattered (throughout much of Africa) and is therefore intrinsically disjunctive.

If a population remains disjunct from the rest of the species' populations it may become extirpated due to an inability to adapt to its new environment or be rescued by nearby populations. However, if the population is able to adapt to its new environment speciation may occur due to the lack of gene flow with other populations and an accumulation of local adaptations.^[1][2] Although it can be difficult to determine if speciation is truly occurring, the degree of speciation of a disjunctive population can be determined using molecular, chromosomal, and morphological approaches.^[3] Historical examples of speciation can also be used to characterize the process of speciation when caused by a disjunctive population, such as that of the Virginia opossum, Didelphis virginiana. They are the only extant marsupial species found in North America because some of their ancestors migrated from South America during the Great American Interchange and were then cut off from South American populations when the Isthmus of Panama closed.^[4]

See also

• Disjunct distribution
• Ecological island
• Habitat fragmentation
• Population fragmentation