I am going to go out on a limb and suggest that many, if not most, parasite species exploit several to many hosts species, for a given stage of their (i.e., the parasite’s) life cycle. The question of why such parasite species are catholic in their diet (I say diet because, really, the host is a source of food for the parasite’s growth, development and/or reproduction), remains largely an open question. One interesting nuance is that a given species of parasite often has differential fitness or success on different host species (here, we are controlling for time and location of collection of both the parasite and host species). A troubling issue is why the parasite has not evolved discrimination, another is why some host species are better hosts than others, a third is whether there are alleles coding for host species use that are in competition with one another. There are several other questions such as how important is host species relative frequency across space and time in determining whether it is a principal species exploited by the parasite and what, if any, trade-offs exist in using one species over another. We are just starting to get answers to these questions. Sometimes, nature pitches real oddities at you. Consider, two damselfly species where one is totally susceptible to a mite ectoparasite and the other is totally susceptible. If you want to getthe scoop, visit Julia Mlynarek’s blog: Julia was one of my PhD students here art Carleton University.
Professor & student