Phylogenetic tree of the human lysophospholipid-binding receptors, together with the next closest group of human cannabinoid receptors.

GPR45 is the mammalian orthologue of the Xenopus laevis LPA receptor PSP24.37 The numbers indicate the percentage of divergence. EDG-6 is more closely related to the SPP-binding receptors EDG-1, EDG-3, and EDG-5 than to the LPA-binding receptors EDG-2 and EDG-4.