Calculate the overlap metrics D and I based on two species occurrence density grids z1 and z2 created by
Species 1 occurrence density grid created by
Species 2 occurrence density grid created by
Correct the occurrence densities of each species by the prevalence of the environments in their range (TRUE = yes, FALSE = no).
if cor=FALSE, the z$uncor objects created by
ecospat.grid.clim are used to calculate the overlap. if cor=TRUE, the z$cor objects are used.
If you encounter a problem during your analyses, please first read the FAQ section of "Niche overlap" in http://www.unil.ch/ecospat/home/menuguid/ecospat-resources/tools.html
Overlap values D and I. D is Schoener's overlap metric (Schoener 1970). I is a modified Hellinger metric(Warren et al. 2008)
Olivier Broennimann [email protected]
Broennimann, O., M.C. Fitzpatrick, P.B. Pearman, B. Petitpierre, L. Pellissier, N.G. Yoccoz, W. Thuiller, M.J. Fortin, C. Randin, N.E. Zimmermann, C.H. Graham and A. Guisan. 2012. Measuring ecological niche overlap from occurrence and spatial environmental data. Global Ecology and Biogeography, 21, 481-497.
Schoener, T.W. 1968. Anolis lizards of Bimini: resource partitioning in a complex fauna. Ecology, 49, 704-726.
Warren, D.L., R.E. Glor and M. Turelli. 2008. Environmental niche equivalency versus conservatism: quantitative approaches to niche evolution. Evolution, 62, 2868-2883.
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