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Hosts can avoid parasites (and pathogens) by reducing social contact, but such isolation may carry costs, e.g. increased vulnerability to predators. Thus, many predator–host–parasite systems confront hosts with a trade-off between predation and parasitism. Parasites, meanwhile, evolve higher virulence in response to increased host sociality and consequently, increased multiple infections. How does predation shift coevolution of host behaviour and parasite virulence? What if predators are selective, i.e. predators disproportionately capture the sickest hosts? We answer these questions with an eco-coevolutionary model parametrized for a Trinidadian guppy–Gyrodactylusspp. system. Here, increased predation drives host coevolution of higher grouping, which selects for higher virulence. Additionally, higher predator selectivity drives the contact rate higher and virulence lower. Finally, we show how predation and selectivity can have very different impacts on host density and prevalence depending on whether hosts or parasites evolve, or both. For example, higher predator selectivity led to lower prevalence with no evolution or only parasite evolution but higher prevalence with host evolution or coevolution. These findings inform our understanding of diverse systems in which host behavioural responses to predation may lead to increased prevalence and virulence of parasites.
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Winter Tick Burdens for Moose Are Positively Associated With Warmer Summers and Higher Predation Rates
Climate change is expected to modify host-parasite interactions which is concerning because parasites are involved in most food-web links, and parasites have important influences on the structure, productivity and stability of communities and ecosystems. However, the impact of climate change on host–parasite interactions and any cascading effects on other ecosystem processes has received relatively little empirical attention. We assessed host-parasite dynamics for moose ( Alces alces ) and winter ticks ( Dermacentor albipictus ) in Isle Royale National Park over a 19-year period. Specifically, we monitored annual tick burdens for moose (estimated from hair loss) and assessed how it covaried with several aspects of seasonal climate, and non-climatic factors, such as moose density, predation on hosts by wolves ( Canis lupus ) and wolf abundance. Summer temperatures explained half the interannual variance in tick burden with tick burden being greater following hotter summers, presumably because warmer temperatures accelerate the development of tick eggs and increase egg survival. That finding is consistent with the general expectation that warmer temperatures may promote higher parasite burdens. However, summer temperatures are warming less rapidly than other seasons across most regions of North America. Therefore, tick burdens seem to be primarily associated with an aspect of climate that is currently exhibiting a lower rate of change. Tick burdens were also positively correlated with predation rate, which could be due to moose exhibiting risk-sensitive habitat selection (in years when predation risk is high) in such a manner as to increases the encounter rate with questing tick larvae in autumn. However, that positive correlation could also arise if high parasite burdens make moose more vulnerable to predators or because of some other density-dependent process (given that predation rate and moose density are highly correlated). Overall, these results provide valuable insights about interrelationships among climate, parasites, host/prey, and predators.
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- Award ID(s):
- 1939399
- PAR ID:
- 10313456
- Date Published:
- Journal Name:
- Frontiers in Ecology and Evolution
- Volume:
- 9
- ISSN:
- 2296-701X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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ABSTRACT Predation can alter diverse ecological processes, including host–parasite interactions. Selective predation, whereby predators preferentially feed on certain prey types, can affect prey density and selective pressures. Studies on selective predation in infected populations have primarily focused on predators preferentially feeding on infected prey. However, there is substantial evidence that some predators preferentially consume uninfected individuals. Such different strategies of prey selectivity likely modulate host–parasite interactions, changing the fitness payoffs both for hosts and their parasites. Here we investigated the effects of different types of selective predation on infection dynamics and host evolution. We used a host–parasite system in the laboratory (Daphnia dentifera infected with the horizontally transmitted fungus,Metschnikowia bicuspidata) to artificially manipulate selective predation by removing infected, uninfected, or randomly selected prey over approximately 8–9 overlapping generations. We collected weekly data on population demographics and host infection and measured susceptibility from a subset of the remaining hosts in each population at the end of the experiment. After 6 weeks of selective predation pressure, we found no differences in host abundance or infection prevalence across predation treatments. Counterintuitively, populations with selective predation on infected individuals had a higher abundance of infected individuals than populations where either uninfected or randomly selected individuals were removed. Additionally, populations with selective predation for uninfected individuals had a higher proportion of individuals infected after a standardized exposure to the parasite than individuals from the two other predation treatments. These results suggest that selective predation can alter the abundance of infected hosts and host evolution.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fevo.2021.758374
