The relationship between species richness and area is a rectangular hyperbola, it is a straight line on a logarithmic scale. The curve is often referred to as the species–area curve. The first mathematical description of the species–area relationship was proposed by Arrhenius in 1920 and modified by Gleason in 1922. S=CAZ log S = log C + Z log A where, S = species richness, A = area, Z = the slope of the line (regression coefficient) and C = the intercept on the y axis.