(coaster) writes:

I'm not sure if this is the place to ask, but I was led to believe that
there existed trees that were so old, unique species had evolved on them. Is
this true?

Not individual trees, but species of trees sometimes associate with other
plants and animals. For instance, there is a species of acacia that had
developed a commensal relationship with a species of ant. The tree feeds
the ants with nectar, and the ants defend the tree from all other insect
invaders.

The association between mistletoe and oak is well known. Almost every
species of tree has parasites and pathogens that are specific to that
species.

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