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The species–area relationship or species–area curve describes the relationship between the area of a habitat, or of part of a habitat, and the number of species found within that area. Larger areas tend to contain larger numbers of species, and empirically, the relative numbers seem to follow systematic mathematical relationships. [ 1 ]
The species-area relationship equation is: =. [10] An example of what a species-area relationship may look like when graphed. In this equation, represents the measure of diversity of a species (for example, the number of species) and is a constant representing the y-intercept.
The species–area relationship relating the number of species found in an area as a function of the size ... the slope of the straight line corresponds to the power ...
Smith in 1938 while studying crop yields proposed a relationship similar to Taylor's. [22] This relationship was = + where V x is the variance of yield for plots of x units, V 1 is the variance of yield per unit area and x is the size of plots. The slope (b) is the index of heterogeneity.
Then = for some constant k, and if this relationship were exactly true, the species area line would be straight on log scales. It is typically found that the curve is not straight, but the slope changes from being steep at small areas, shallower at intermediate areas, and steep at the largest areas.
Blackburn and Gaston 1997 tested the effect of removing tropical species on latitudinal patterns in avian species richness in the New World and found there is indeed a relationship between the land area and the species richness of a biome once predominantly tropical species are excluded. Perhaps a more serious flaw in this hypothesis is some ...
The rank abundance curve visually depicts both species richness and species evenness. Species richness can be viewed as the number of different species on the chart i.e., how many species were ranked. Species evenness is reflected in the slope of the line that fits the graph (assuming a linear, i.e. logarithmic series, relationship).
Another hypothesis that is cited to explain the upper limit of the elevational diversity gradient is the area hypothesis, which states that larger areas can support more species. As elevation increases, total area decreases; thus, there are more species present at middle elevations than at high elevations.