According to AV Humboldt, a German scientist, within a region, species richness increases with increase in explored area (only upto a limit). Accordingly the relation between species richness and area for a wide variety of taxa (birds, bat, angiosperms, aquatic fishes) turns out to be a rectangular hyperbola. The relationship depicts a straight line on a logarithimic scale described by the following equation
log S = log C + Z log A
Where, ‘S ’ stands for species richness, ‘A’ is area and ‘Z’ and ‘C are slope of line (regression coefficient) and y intercept respectively.