“Know thyself”

Sage advice, particularly if you are a hermaphrodite organism seeking to take advantage of sexual reproduction. Promotion of out-breeding requires that male gametes do not fertilize the eggs being released from the same organism, or only do so at very low effi ciency. This problem impacts a variety of organisms from fl owering plants (Rea & Nasrallah, 2008) to ascidians, the sea squirts. Indeed the basic process is equally fundamental to the vertebrate immune response (Burnet, 1971). Interestingly the receptor/ligand pairs that mediate gamete self/non-self discrimination (allorecognition) are not phylogenetically conserved, indicating that these systems are a striking example of convergent evolution.