Species-Area relationships - Practice Questions & MCQ

• German naturalist and geographer Alexander von Humboldt carried out extensive explorations in the wilderness of South American jungles observed that within a region species richness increased with increasing explored area, but only up to a limit. 
• In fact, the relation between species richness and area for a wide variety of taxa
• (angiosperm plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola.
• On a logarithmic scale, the relationship is a straight line described 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 (unit of measurement of area)
• The relationship between S, C and A for a rectangular hyperbola is given as:
  • S = CA^Z
• Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region (whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are amazingly similar).
• But, if you analyse the species-area relationships among very large areas like the entire continents, you will find that the slope of the line to be much steeper (Z values in the range of 0.6 to 1.2). For example, for frugivorous (fruit-eating) birds and mammals in the tropical forests of different continents, the slope is found to be 1.15.
• Steep slope in this case signifies the increased species richness for a vast area of continent under study.