A student studying tree species diversity uses a large number of sampling quadrats (each of 1-hectare area) to cover >50% of the area of a 200-hectare tropical forest patch. Consider the statements in the options below:

A. Species numbers increase with sampling area following a power-law relationship with exponent >0 and <1.
B. The log of species numbers increases linearly with the log of the sampling area.
C. Species numbers increase with sampling area following a power-law relationship with exponent >1.
D. Species numbers increase linearly with the log of the sampling area.

Which combination of the statements above describes the expected pattern?

Correct option is A

Explanation:

• The species-area relationship is commonly described by the power-law:

  S= cA^z​

  where ,

• $S$ = species number, $A$ = area, $c$ = constant, and $z$ = exponent.

• Empirical studies show that the exponent $z$ usually lies between 0 and 1, indicating a sublinear increase in species number with area.

• Taking logarithms gives : log S=log c+ z log A

• showing a linear relationship between $\log S$ and $\log A$.

• Therefore, statements A (exponent between 0 and 1) and B (linear log-log relationship) correctly describe the species-area pattern.

• Statement C (exponent > 1) is incorrect because it would imply a superlinear increase, which is ecologically unrealistic.

• Statement D suggests a linear increase of species with $\log A$, which misrepresents the power-law model.

Information Booster:

• The species-area relationship is fundamental in ecology for estimating biodiversity and conservation planning.

• Typical $z$ values range from 0.1 to 0.4 for continental areas.

• Log-log plots are used to linearize the relationship and estimate parameters.