Just for the record, three major kinds of symbiosis are parasitism,
mutualism, and commensalism. So stating that parasitism will evolve
into symbiosis is redundant, since parasitism already is a symbiosis.

Thomas W. Culliney

Thanks for the clarification. However, terms are used differently by scientists, experts, and the general population. 

The standard definition of symbiosis runs "interaction between two different organisms living in close physical association, typically to the advantage of both" whereas "Parasites ... cause varying degrees of damage or disease to the host".

How do you square these two concepts? That is, how can a relationship be symbiotic if it kills the host? Further, when varroa first attacked Apis mellifera, it was symbiotic with Apis cerana but not A. mellifera. 

So, it was a parasite in A. c. first, changing hosts to A. m. and developing a relationship which usually kills the host colony. The varroa move on to other colonies. Were it not for beekeeper intervention, it is entirely possible that varroa could kill all bees in an area and then go extinct itself, in that area.

In other words, it is not inevitable that a mutualism, commensalism or whatever you want to call it, will ever occur -- although it does in fact occur in some populations (Apis mellifera scutellata, for example). 

PLB

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