I've used the FORTRAN based NODF Program (Ulrich 2012) to investigate nestedness patterns among communities from a set of habitat fragments. I've run the analyses using presence-absence based null models (NODF) and also using abundance based null models (WNODF). When a presence-absence based null model is run, the program returns only NODF scores. However, when an abundance based model is run, the program returns both WNODF scores and NODF scores. My question concerns NODF scores/results. The NODF results returned from running an abundance based null model versus the NODF results from running a presence-absence based null model are very different. Given these are both presumably based on presence-absence data, seems they should be qualitatively and quantitatively very similar. I've gone to a number of the original papers but I'm not finding anything that would explain why these results would differ. I would greatly appreciate an explanation from anyone that has insight on the subject.
Thanks much!
- Badges
- Science topic