Figure 4. Null distribution of the ß-diversity of
interactions (ßTL) at fixed trophic group diversity. The values of the
histogram show the ßTL between the average food webs of forest and
grassland computed using 3000 permutations of trophic group abundances
at fixed network structure, leading to various ßTL values while keeping
trophic group ß-diversity constant. The vertical line shows the observed
ßTL across habitats. The value of ßTL varies from one when the average
food web of forest and grassland have identical interaction abundances
distribution, to two, when the food webs do not share any common group
or interaction.