Figure 3

SADs of Pico and Terceira islands for arthropod species groups with high and low dispersal abilities. Each curve corresponds to the average of all possible SAD curves obtained by using the concentric procedure as explained in the Methods. The x-axis corresponds to classes of the logarithm of base 2 of the number of individuals as follows: 1 individual, 2 to 3 individuals, 4 to 7 individuals, et seq. In order to better illustrate the evolution of the shapes of the distributions, the curves have a gradient of colours going from black (the smallest number of transects), through green and blue, to red (the largest number of transects). In all cases we can observe the development of humps when the number of transects increases. However, while for species with high dispersal ability the number of singletons keeps increasing with the number of transects, for species with low dispersal the number of singletons decreases for the largest number of transects; in fact, for Terceira, when a large number of transects is added, the absolute maximum no longer occurs for the singleton abundance class, but for some intermediate classes.