I am having trouble finding examples of symbiotic relationships that are obligate for one organism involved and facultative for the other. I.e, one organism needs its partner to survive, but the other can survive perfectly well on its own. Do you know of any?

What about Wolbachia infection in Drosophila? The Wolbachia can't survive outside the host cells and is transmitted vertically through the germline, but the fly is perfectly fine without it.

Last edited by Jessica Cande (13th Jun 2013 13:15:52)