Many parasites complete their life cycle by first developing in an intermediate host, then reproducing in a definitive host, relying on predation of intermediate hosts by definitive hosts. Consequently, these parasites are embedded in food webs. The structure of these food webs creates a selective force; if definitive hosts are choosy feeders then any parasite strategy can be viable, provided it involves infection of the definitive host’s meal. However for definitive hosts that eat almost anything, parasites are more generalist in terms of which prey they infect. This is predicted by theory only if there are low costs of generalism.
This paper is available online:
Park AW. 2019 Food web structure selects for parasite host range. Proc. R. Soc. B 20191277. http://dx.doi.org/10.1098/rspb.2019.1277