APES CH 5 (modules 14-17) Reading guides Imagine a community of 100 individuals that are evenly divided among four species, so that the
proportions (p) of the species all equal 0.25. We can calculate Shannon's index as follows:
H = -f(0.25 x In 0.25) + (0.25 x in 0.25) + (0.25 x in 0.25) x (0.25 x in 0.25)]
H=-(-0.35) + (-0.35) + (-0.35) + (-0.35))
H = 1.40
Now imagine another community of 100 individuals that also contains four species, but in which one
species is represented by 94 individuals and the other three species are each represented by 2
individuals. We can calculate Shannon's index to see how this difference in species evenness affects
the value of the index:
H = -(0.94 x in 0.94) + (0.02 in 0.02) + (0.02 x in 0.02) + (0.02 * in 0.02)]
H=-(-0.06) + (-0,08) + (-0.08) + (-0.08)
H=0.30
Because this value of His lower than the value we calculated for the first community, we can
conclude that the second community has lower diversity. Note that the total number of individuals
does not affect Shannon's index of diversity, only the number of species and the proportion of
individuals within each species matter.
Your Tum: Imagine a third community of 100 individuals in which those individuals are distributed
evenly among all the species, but there are only two species, not four. Calculate Shannon's index to
see how this difference in species richness affects the value of the index