What percent of species extinctions are caused by parasites?

Next week, I’m going to talk about parasite-driven species extinctions. But first I thought it’d be fun to take a little poll. In our current mass extinction, what percentage of species extinctions do you think have been caused (i.e., extinct species) or nearly-caused (i.e., endangered species) by parasites, pathogens, or viruses? Round your answer to the nearest 10%.

This would be a good disease ecology prelims question.

3 thoughts on “What percent of species extinctions are caused by parasites?

  1. This is interesting because you would think that a parasite wouldn’t ‘want’ its host to go extinct because then the parasite could potentially go extinct. Just as a predator without prey no longer exists. I’ve not thought about parasites causing extinctions. I would assume a parasite-driven extinction of a host would come about in concert with some other extinction force (e.g., competition, climate, humans). I look forward to the post!

    • Thanks for the comment!

      There is an argument for killing hosts to be selected against for (some) parasites, leading to the evolution of intermediate virulence. If the parasite causes too much damage in it’s race to replicate in the host, the host might die before the parasite is ever transmitted. So less virulent strains can be selected for.

      But of course, sometimes killing the host is an effective route for transmission (e.g., trophic transmission).

      • Yes. Good point of trophic transimission where host death is necessary for transmission. Would argue then for intermediate virulence at least in definitive hosts.

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