Dear all,
I'm running the D and I overlap test metrics adapted for Warren, 2008 - 2010 in the ENMTools. According to Warren, D have ecological significance, while I test shows the comparison as a probability of distribution.
Have you used these metrics? how you explain the differences in the values of both tests?
Thank you very much in advance!
Ricardo
Hi Ricardo,
The traditional D metric used for calculating the overlap/similarity of two or more species niche according to direct ecological observations/datasets (see Schoener, 1968, Ecology). Whereas, the traditional Hellinger distance metric (I) used for measuring the difference between two probability distributions (mathematical studies back to 1900s), and it was modified for ecological studies (see Warren, 2008, Evolution).
The ENMTools uses the (normalized) (modelled) suitability of occurrence of studied species in a defined space (i.e. study area) to calculate D and I metrics by comparing each grid in the study area between two species or time periods, etc.
D and I metrics (calculated from ENM) represent same ecological information. But, sure, these metrics are strictly linked to how you built distribution models. The difference between the calculated D and I is just because of their formulations. I can recommend you to read Rödder & Engler, 2011, Global Ecology and Biogeography.
Cheers,
Semra
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