Q. Explain about gamma diversity?

Gamma (g) richness refers to the rate of change across larger landscape gradients and gamma diversity is a measure of the overall diversity for different ecosystems in a region. Hunter defines gamma diversity as " geographic-scale species diversity". Let us make this concept more clear to you by giving an example. Suppose we want to compare diversity of hypothetical species in different ecosystems say I, II and III.

We can walk a transect in each of these three e cosystems and count the number of species we see, this gives us the alpha diversity for each ecosystem, e.g. a diversity of ecosystem I, II and III is 10,7, and 3 reap. Now, if we examine the change in species diversity between these ecosystems then we are measuring the b diversity, e.g. beta diversity between I and II is 7(representing 5 found in ecosystem I but not in ecosystem II plus 2 species found in ecosystem II but not in I), similarly b diversity between ecosystem II and III is 8 and between ecosys tem I and III is 13.