We tested for differences between the distributions of abundances
(ROAPs) among each pair of forest types using a resampling
procedure.
we sampled the data
1000 times, randomizing forest type among the samples
For each
run, we calculated the area between the two ROAPs, a statistic we
refer to as D⁄.
A large value of D⁄ can reflect differences in mean
abundance, or differences in the heterogeneity of abundances
among sites, or both.
For each species, we calculated the D. for each
of the three possible pairwise combinations of forest types. The area
was calculated as the integral of the absolute value of the difference
between distributions; if the ROAPs crossed once, the two sub-areas
were added (so D. was always positive). Finally, we compared the
empirical D. to the distribution generated by randomization and
considered results significant for p < 0.05 using a one-sided test
(i.e., a high observed D.). We applied a correction for multiple tests,
controlling for false discovery rate by setting a threshold of 0.05 (61
total tests: 13 species for which we performed one habitat pair
comparison plus 16 species for which we conducted three habitat
pair comparisons; Benjamini and Hochberg, 1995).