Biogeographical Regions

Abstract Species are not uniformly distributed over the globe. The largest regions of animal and plant assemblages are biogeographical regions, each bearing a distinctive fauna and flora. Some families and even some orders of animals are endemic to particular biogeographical regions; other families are shared by two or more regions; a few families are cosmopolitan and found in all regions. The delineation of traditional biogeographical regions was rather subjective. Recently, increased availability of global species range maps, the development of new multivariate techniques and improved computational power have led to quantitative regionalisations that are broadly similar to traditional regions but do show differences. The transition zones between are sometimes gradual, as in the junction between the Oriental and Australian faunal regions. The state of biogeographical regions is under threat from such human activities as habitat destruction and fragmentation and the introduction of alien species, and it will decline without conservation measures. Key Concepts: Regions (in biogeography) are spatial units of varying scales carrying comparatively distinct sets of animals and plants. Faunal and floral elements are groups of species sharing a similar pattern of geographical distribution. Biogeographical provincialism is the tendency of different geographical regions to house unique species, genera or families. Endemism is the state of being unique to a specific geographical region, such as a continental landmass, a biogeographical region or a habitat. Transition zones (in biogeography) are regions where one biogeographical region grades into another, and contrasts with sharp borders. The Great American Interchange was the intermingling of South American and North American faunas starting 6 million years ago when a string of islands and then a permanent land connection bridged the ocean gap between North American and South American landmasses. Habitat loss and fragmentation is one of the chief drivers of biodiversity loss and change in biogeographical regions. Alien species (also called exotic, introduced and nonnative species) are species accidentally or purposefully carried to areas outside their natural range by humans.