The importance of parasites for the conservation of diversity on earth?

Parasites force hosts to adapt to their presence, thereby stimulating their evolution. They affect their numbers, destroying the weakest individuals; some parasites are also capable of influencing the reproductive potential of the host.

They can help their owners to protect their habitat from alien competitive populations. After all, the population that coexisted with a certain parasite for a long time has developed resistance to it, and for the newly arrived population, the parasite will turn out to be much more pathogenic and dangerous.