What is parasite ecology?

Since you’re reading a blog called Parasite Ecology, you probably already know what a “parasite ecologist” studies. If you do, you’re a member of a global minority – congratulations! Your membership ID card will be arriving in the mail any day now.

If I had a nickel for every time someone asked me what “parasite ecologists” study, or came to the blog after Googling “what is parasite ecology?”, I could buy another pumpkin latte today. In some ways, it’s weird that I’m asked this so often, because I don’t go around introducing myself as a parasite ecologist. (I think my job prospects are better if I sell myself more broadly to other scientists, and I think my communication with non-scientists is more effective if I say that I study “infectious diseases in wildlife and sometimes people, like rabies.”) But because I have a Parasite Ecology blog – maybe even The Parasite Ecology Blog? – I suppose I am The Chosen Answerer of This Question. So, here it is:

Parasite ecologists study the ecology of parasites: the interactions between parasites (or pathogens), hosts, and their (abiotic and biotic) environments.

If you’re looking for something more specific, I also made you this word cloud to illustrate the terms that parasite ecologists used the most in 2017 publications.* Like other types of ecologists, parasite ecologists want to understand the distribution and abundance of individual species, as well as the processes that affect species diversity. To do that, we study individuals, populations, and communities. Sometimes we study the effects of parasites on ecosystems and/or the effects of ecosystems on parasites, but ecosystem-level studies aren’t as common in this subfield, as is corroborated by the fact that ecosystems didn’t make it into the word cloud.

WordCloud115WordsV2.png

So there you have it! But perhaps you’re thinking, “Wait, that sounds like disease ecology. What’s the difference?” The answer is that parasite ecology = disease ecology. But I think that parasite ecology is a better term, because not all infected hosts are diseased.

If you want to complicate matters further, have you seen my old post about the difference between disease ecology and parasitology? 😛

*To make the word cloud, I performed an ISI Web of Knowledge search for all papers published in 2017 that contained the terms parasit* AND ecology. I performed the search on 28 October 2017, and it picked up several papers from November journal issues. I used the titles and abstracts from all 410 papers to create the word cloud. (I didn’t filter the papers at all, so there are probably a few papers in the dataset that aren’t highly relevant.) If you would like to make your own word cloud, you can access the data and the R code on my GitHub.

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?

Most Prolific Parasite Ecologists of the 21st Century

I had a lot of fun playing on Web of Science last week when I was trying to figure out whether parasitism is underrepresented in the ecological literature.  At one point, I accidentally sorted by author instead of journal, and I realized that I could easily generate a list of The Most Prolific Parasite Ecologists of the 21st Century!  And so I did!

I searched Web of Science for any papers with parasit* as the topic, while excluding anything with parasitoid as the topic.  I only searched in the years 2001 to 2013, because apparently the year 2000 doesn’t count as the 21st century.  Finally, I narrowed the search results down to include only these journals: PNAS, Proceedings of the Royal Society B, Oecologia, Oikos, Ecology, American Naturalist, Journal of Animal Ecology, Ecology Letters, Functional Ecology, Trends in Ecology Evolution, Ecological Applications, Journal of Applied Ecology, and Journal of Ecology. Using this method, the top 30 most prolific parasite ecologists of the 21st century are:

  1. HIDDEN MOMENTARILY FOR DRAMATIC EFFECT
  2. AP Moller
  3. PJ Hudson
  4. KD Lafferty
  5. BR Krasnov
  6. H Richner
  7. M Boots
  8. D Ebert
  9. PTJ Johnson
  10. AF Read
  11. LH Miller
  12. A Buckling
  13. FJ Ayala
  14. JC de Roode
  15. MA Duffy
  16. SR Hall
  17. P Schmid-Hempel
  18. S Morand
  19. CE Caceres
  20. J Jokela
  21. AM Kuris
  22. S Gandon
  23. IS Khokhlova
  24. D Mouillot
  25. RE Ricklefs
  26. WH van der Putten
  27. S Altizer
  28. DH Clayton
  29. T Day
  30. A Fenton

And the Golden Cercariae Award for The Most Prolific Parasite Ecologist of the 21st Century goes to: Robert Poulin!  Runners up get free access to everything on the Parasite Ecology blog for a year.  😉

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So, my search method obviously had some issues.  For instance, a few people who are probably more parasitologists than parasite ecologists made it onto the list, most likely because I included PNAS in my list of journals.  Also, the exact order of authors is a bit finicky, because some authors only differed by one or two publications.  That means that including slightly different journals might jumble the order.  But in general, I’d say that this is a pretty good list!  If you’re wondering, you needed to get at least 13 publications in the journals that I listed to make it in the top 30 – roughly one publication per year, on average.

Who do you think the Most Prolific Parasite Ecologist of the 20th Century was?