Question

Explain the species-area relationship using the graphical representation given below:

or

The following graph shows the species-area relationship. Answer the following questions as directed.

1. Name the naturalist who studied the kind of relationship shown in the graph. Write the observations made by him.
2. Write the situations as discovered by the ecologists when the value of ‘Z’ (slope of the line) lies between:
   1. 0.1 and 0.2
   2. 0.6 and 1.2
      What does ‘Z’ stand for?
3. When would the slope of the line ‘b’ become steeper?

Answer 1

(a) Alexander von Humboldt noted that species richness within a region grew with increased exploration, but only up to a certain point. The relationship between species richness and area for several taxa, including angiospermic plants, birds, bats, and fishes, follows a rectangular hyperbola pattern. On a logarithmic scale, the relationship is a straight line represented by the equation.

log S = log C + Z log A

where, S = species richness

A = area

z = slope of the line (regression coefficient)

C = Y-intercept

(b) (i) Ecologists found that Z values vary from 0.1 to 0.2, regardless of taxonomic group or region, while exploring a restricted region.

(ii) When analyzing species-area relationships over huge areas, such as continents, the slope of the line is significantly steeper (Z values ranging from 0.6-1.2).
‘Z’ stands for the regression coefficient (slope of the line).

(c) The slope of the line ‘b’ will become steeper when the explored area is increasing.