Idiosyncratic species may be identified by an idiosyncratic temperature higher than the system temperature of the matrix.
System temperature is denoted with a horizontal line.
Because the idiosyncratic species elevate the temperature of the matrix of the whole, an idiosyncratic temperature at or greater than system temperature implies that the species is in some manner disconnected form the system-wide biogeography of the archipelago. The majority of species occur in both island sets, but some appear only in one or the other set of islands. That disjunction in species composition creates the idiosyncratic species temperatures shown.