Species–area relationship

[1] The species–area relationship is usually constructed for a single type of organism, such as all vascular plants or all species of a specific trophic level within a particular site.

It is rarely if ever, constructed for all types of organisms if simply because of the prodigious data requirements.

Ecologists have proposed a wide range of factors determining the slope and elevation of the species–area relationship.

[2] These factors include the relative balance between immigration and extinction,[3] rate and magnitude of disturbance on small vs. large areas,[3] predator-prey dynamics,[4] and clustering of individuals of the same species as a result of dispersal limitation or habitat heterogeneity.

[6] In contrast to these "mechanistic" explanations, others assert the need to test whether the pattern is simply the result of a random sampling process.

[9] Regardless of census design and habitat type, species–area relationships are often fitted with a simple function.

Frank Preston advocated the power function based on his investigation of the lognormal species-abundance distribution.

which looks like a straight line on semilog axes, where the area is logged and the number of species is arithmetic.

[10] Species–area relationships are often graphed for islands (or habitats that are otherwise isolated from one another, such as woodlots in an agricultural landscape) of different sizes.

In contrast, species–area relationships for contiguous habitats will always rise as areas increases, provided that the sample plots are nested within one another.

The species–area relationship for mainland areas (contiguous habitats) will differ according to the census design used to construct it.

In the first part of the 20th century, plant ecologists often used the species–area curve to estimate the minimum size of a quadrat necessary to adequately characterize a community.