Tag Archives: parasitism


First, to clear the air, yes we know catfish don’t have cat ears but he’s on his way to a masquerade ball!

Second, it comes highly recommended that you check out the entire thread that inspired this comic (see below) because mussels are absolute legends when it comes to making lures to, well, lure in some unsuspecting fishies.

Tanya Strydom is a PhD candidate at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.

It Takes A Village

Testing the parasite-mediated competition hypothesis between sympatric northern and southern flying squirrels (2022) O’Brien et al. 2022, International Journal for Parasitology: Parasites and Wildlife, https://doi.org/10.1016/j.ijppaw.2021.11.001

Image credit: Stephen Durrenberger, CC BY-NC-SA 2.0, Image Cropped

The Crux

One consequence of climate change is that organisms move to new habitats, as they try and track suitable environmental conditions. This can result in closely related species coming into contact with one another, which in turns drives competition among these organisms. Competition between these organisms can manifest as either direct competition (where two organisms directly compete with one another for food or habitat), but it can also manifest as apparent competition.

Apparent competition happens when species A serves as a food source for predators or parasites, which increases the numbers of predators/parasites in the environment. This increase in predators or parasites then puts more pressure on species B. Apparent competition via parasitism was actually a major driver for the decline of red squirrels in the UK, as the introduced grey squirrel brought along squirrelpox virus that had severe effects on the red squirrels.

If one species is more tolerant to a parasite than another, this can result in competitive exclusion, where one species outcompetes the other species to such an extent that the outcompeted species goes locally extinct. This is particularly important when a climate-mediated range expansion brings two species together that share parasites. Today’s authors sought to quantify how infection by parasites affected a vulnerable population after a range expansion by a potential reservoir species.

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Better Means Faster

Species interactions have predictable impacts on diversification (2021) Zeng and Wiens, Ecology Letters. https://doi.org/10.1111/ele.13635

Image Credit: MacNeil Lyons/NPS, CC BY 2.0

The Crux

No organism on the planet lives in complete isolation from other organisms. Many organisms serve as a food source for others, and even apex predators have to compete for their food. Species interactions like predation, competition, and parasitism directly impact organisms in their daily lives, but there is also a possibility that these same species interactions have had an impact on much longer timescales. That is, species interactions may have had a direct effect on the diversity of life on our planet.

Species interactions have been previously shown to affect diversification rates (see Did You Know?), so the question that today’s authors asked was whether there is a general trend to the effects of species interactions on diversification rates? Specifically, do species interactions with negative fitness (such as being killed by a predator) impacts decrease diversification rates, and do species interactions with positive fitness (such as successfully parasitizing a host) impacts increase diversification rates?

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Getting Better May Get You Eaten

Fighting off an infection can use up valuable energy, and also change behaviour, which can lead to enhanced risk of predation

Image Credit: Gilles San Martin, CC BY-SA 2.0, Image Cropped

Immune response increases predation risk (2012) Otti et al., Evolution 66

The Crux

Parasites and diseases cause a lot of problems for their hosts, stealing resources like blood, food and energy. But fighting off parasites is also a costly process, so hosts have to walk the thin line between using just enough resources to fight off the parasite and using too many, leaving them with nothing. The amount a host invests in their immune response will depend on the specific environment that they live in. For example, in an environment where resources are plentiful, a host may decide that it is worth shaking off a parasite or disease. In areas where resources aren’t, they may choose to save energy.

Introducing predation to a situation further complicates things. Having a lot of predators around naturally means energy conservation becomes even more important. This study examines the risk of predation for an organism that is fighting off an infection.

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