https://phys.org/news/2018-05-world-parasites.html

The world is full of parasites and their antagonistic interactions with hosts can have big evolutionary consequences. Virtually all organisms are infected with parasites or are one themselves. Heavily infected hosts can be under strong natural selection as they are unlikely to reproduce. Hosts can reciprocally impose strong selection on parasites as resistant hosts can fight them off, crippling parasite ability to establish an infection and reproduce. This intense, mutual antagonism can drive rapid evolutionary change and is thought to be responsible for many other aspects of biology, from sex to speciation.

Hosts are often under attack from multiple different parasite species. We tested whether this parasite diversity shapes the mutual antagonism with hosts over evolutionary time (e.g. coevolution).