It has been postulated that many species/species interactions don't allways result in one species dying out. The interaction can result in shades ranging from 100% antagonistic to symbiotic. Some plant fungal interactions (think mycorhiza probably evolved this way. this is a system that evolved into one benificial to both organisms. I think that the facets of such relationships can be much more complex than just one organism endangering the fate of another based on paricitism/predation/etc. There are layers of interactions. For example two organisms meet and affect each other ( a straight forward act of paricitism) but then this new association could allow other systems (viral,bacterial,etc) further afffecting the whole interaction. Interspecific exchange of virus or bacteria that were formally not thought possible further affect the relationship. It becomes quite complex the further one looks into these associations the more interactions at a macroscopic and microscopic scale become apparent. Just my angle. Mike >Why is it that the direct ancestors of insects found in resin 42 milion >years old, will today die out in large numbers from the attack of a Varroa >mite of equal pedigree. Surely in all that time similar threats have been >dealt with successfully?