Calculate the overlap metrics D and I based on two species occurrence density grids z1 and z2 created by ecospat.grid.clim.
ecospat.niche.overlap (z1, z2, cor)Species 1 occurrence density grid created by ecospat.grid.clim.
Species 2 occurrence density grid created by ecospat.grid.clim.
Correct the occurrence densities of each species by the prevalence of the environments in their range (TRUE = yes, FALSE = no).
Overlap values D and I. D is Schoener's overlap metric (Schoener 1970). I is a modified Hellinger metric(Warren et al. 2008)
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
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.