Niche expansion and unfilling
Schoener’s D on species occupancy disentangles climate availability and
the extent of niche divergence of clade pairs, but does not take into
account the difference between partial filling and expansion
(Petitpierre et al. 2012). However, expansions measured can characterize
true niche shifts, when native and invaded ranges overlapped in climatic
space, We followed Petitpierre et al. (2012), three categories were
considered in: (1) stable environments where species occurs in both
ranges, (2) unfilled environments where species occur only in the native
range, and (3) expansion environments where the species occur only in
the invaded range.