2014 October Parasite Ecology

Happy October, Everyone!  As you may have noticed, I’ve been slacking in the post department for the past few weeks.  I’m about to cross the finish line on a big deadline – even if I have to wade through crocodile infested swamps while battling fire-breathing dragons to get there – and then I’ll get back to my regular post schedule.  But in the meantime, I thought I’d give you guys a little parasite ecology paper parade.  So, here’s what’s new in parasite (and other symbiont) ecology:

1) If you’re a mutualistic symbiont living on a host, there’s a good chance that you’ll be at a competitive disadvantage in comparison to parasitic symbionts living on the same host.  That’s because you’re providing the host with some service – which presumably isn’t something that you can freely provide – but the parasites aren’t providing any services.  So, how is it that mutualistic species commonly coexist with parasitic ones?  How do mutualistic species evolve in the first place?  Here are some potential answers.

2) High parasite incidence in female guppies at sites with high predation risk may be explained by the fact that female guppies are more likely to shoal at high predation sites, and high host densities can lead to increased parasite transmission.

3) Speaking of the role of density in parasite transmission, for vectored parasites, we expect “encounter dilution,” where the number of vector attacks per host declines with host density (if the vector density remains constant).  Increase host density => decrease risk.  But hosts may also be stressed out and thus more susceptible to parasites at high host densities.  Increase host density => increase risk.  When you combine encounter dilution and density-dependent reductions in immune response, what happens to parasite infection?

4) Mutualists select for later flowering in plants while herbivores select for earlier flowering, so together, there’s no net selection on flowering phenology.  But both mutualists and herbivores select for longer spurs.  Uhm, awesome!

5) Are the strengths of priority effects fixed?  Of course not: everything is context-dependent!  For instance, the presence of parasites can reduce priority effects.

6) And just for fun: are pubic lice going extinct?

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