Vol. 3 - can parasites change food web dynamics?
Parasite-mediated changes in host traits impact food web dynamics.
I vividly remember reading Hudson et al. '06 paper on the fact that parasites can give hints about the health of an ecosystem. It marked the beginning of a shift in my interests, from immunology to parasite ecology.
Over time, my interest in host-parasite associations turned into curiosity about networks, and that eventually brought me to food webs (and later, back to host-virus networks again). All of this is to say: papers about both food webs and parasitism scratch a particular itch for me.
So let's talk about...
Klemme, I., Perälä, T., Lehtinen, S.O. & Kuparinen, A. (2024). Parasite‐mediated changes in host traits alter food web dynamics. Oikos, e10374.
Species interact because their traits allow them to. This seems obvious, but accounting for traits allowed both more prediction of interactions, and a more mechanistic understanding of why interactions happen.
On the other hand, parasites do change host traits all the time. Cases of behavioral changes are well described, but parasites can also change how hosts look, and therefore how they are perceived by potential predators or preys.
In this paper, Klemme et al. are using a simulated aquatic food web to quantify how much tapeworm infection can modify biomass flows. Interestingly, their model reveals strong biomass loss for the infected hosts, but the overall biomass stored in the food web was much less strongly modified.
This result (at least the big picture) was robust to the type of trait change that the parasite created: increased predation, increased maintenance cost, or a combination of both, led to strong effects on host demography, and moderate (but widespread) effects on the food web itself.
I like this paper a lot. A common thread to food web simulations is that the dynamics we get out, especially for species biomass, do not necessarily match the empirical dynamics. In part, this is because we often assume that, when studying a food web, everything must be a trophic interaction. Showing that a single parasite in a pair of hosts can modify their biomass by up to 60% is a strong challenge of this assumption, and hopefully a call to diversify the types of interactions we account for in community models.
Image by Marcel Einig from Pixabay