More Like this

1. The coevolution of parasite virulence and host investment in constitutive and induced defence

   https://doi.org/10.1093/jeb/voaf014  

   Best, Alex; Guth, Sarah; Boots, Mike (April 2025, Journal of Evolutionary Biology)

   Li_Richter, Xiang-Yi; Mullon, Charles (Ed.)

   Abstract Given their ubiquity in nature and their importance to human and agricultural health, it is important to gain a better understanding of the drivers of the evolution of infectious disease. Across vertebrates, invertebrates, and plants, defence mechanisms can be expressed either constitutively (always present and costly) or induced (activated and potentially costly only upon infection). Theory has shown that this distinction has important implications to the evolution of defence due to differences in their impact on both individual fitness and the feedback of the population-level epidemiological outcomes such as prevalence. However, despite the fact that pathogens evolve in response to host immunity and that this can have important implications to the evolution of host defence, the implications of coevolution on constitutive and induced immunity have not been examined. Here we show theoretically how and when incorporating host-parasite coevolution between host defences and parasite growth strategies plays an important role in determining the optimum outcome. A key result is that whether the parasite affects host reproduction critically impacts host-parasite coevolution; when the parasite impacts fecundity, selection on the host is largely geared towards minimizing reproductive costs, through reducing investment in reproductively costly constitutive defence when the parasite prevalence is low, but also by investing in immunity to avoid infection or recover when prevalence is high. Our work emphasizes the importance of coevolution and epidemiological feedbacks to the coevolution of hosts and parasites and provides testable predictions of the determinants of constitutive verses induced defence. 

   more » « less
2. Host and parasite traits predict cross-species parasite acquisition by introduced mammals

   https://doi.org/10.1098/rspb.2021.0341  

   Schatz, Annakate M.; Park, Andrew W. (May 2021, Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   Species invasions and range shifts can lead to novel host–parasite communities, but we lack general rules on which new associations are likely to form. While many studies examine parasite sharing among host species, the directionality of transmission is typically overlooked, impeding our ability to derive principles of parasite acquisition. Consequently, we analysed parasite records from the non-native ranges of 11 carnivore and ungulate species. Using boosted regression trees, we modelled parasite acquisition within each zoogeographic realm of a focal host's non-native range, using a suite of predictors characterizing the parasites themselves and the host community in which they live. We found that higher parasite prevalence among established hosts increases the likelihood of acquisition, particularly for generalist parasites. Non-native host species are also more likely to acquire parasites from established host species to which they are closely related; however, the acquisition of several parasite groups is biased to phylogenetically specialist parasites, indicating potential costs of parasite generalism. Statistical models incorporating these features provide an accurate prediction of parasite acquisition, indicating that measurable host and parasite traits can be used to estimate the likelihood of new host–parasite associations forming. This work provides general rules to help anticipate novel host–parasite associations created by climate change and other anthropogenic influences. 

   more » « less
3. Bidirectional interactions between host social behaviour and parasites arise through ecological and evolutionary processes

   https://doi.org/10.1017/S0031182020002048  

   Hawley, Dana M.; Gibson, Amanda K.; Townsend, Andrea K.; Craft, Meggan E.; Stephenson, Jessica F. (March 2021, Parasitology)

   null (Ed.)

   Abstract An animal's social behaviour both influences and changes in response to its parasites. Here we consider these bidirectional links between host social behaviours and parasite infection, both those that occur from ecological vs evolutionary processes. First, we review how social behaviours of individuals and groups influence ecological patterns of parasite transmission. We then discuss how parasite infection, in turn, can alter host social interactions by changing the behaviour of both infected and uninfected individuals. Together, these ecological feedbacks between social behaviour and parasite infection can result in important epidemiological consequences. Next, we consider the ways in which host social behaviours evolve in response to parasites, highlighting constraints that arise from the need for hosts to maintain benefits of sociality while minimizing fitness costs of parasites. Finally, we consider how host social behaviours shape the population genetic structure of parasites and the evolution of key parasite traits, such as virulence. Overall, these bidirectional relationships between host social behaviours and parasites are an important yet often underappreciated component of population-level disease dynamics and host–parasite coevolution. 

   more » « less
4. Parasitism shapes selection by drastically reducing host fitness and increasing host fitness variation

   https://doi.org/10.1098/rsbl.2022.0323  

   Hasik, Adam Z.; Siepielski, Adam M. (November 2022, Biology Letters)

   Determining the effects of parasites on host reproduction is key to understanding how parasites affect the underpinnings of selection on hosts. Although infection is expected to be costly, reducing mean fitness, infection could also increase variation in fitness costs among hosts, both of which determine the potential for selection on hosts. To test these ideas, we used a phylogenetically informed meta-analysis of 118 studies to examine how changes in the mean and variance in the outcome of reproduction differed between parasitized and non-parasitized hosts. We found that parasites had severe negative effects on mean fitness, with parasitized hosts suffering reductions in fecundity, viability and mating success. Parasite infection also increased variance in reproduction, particularly fecundity and offspring viability. Surprisingly, parasites had similar effects on viability when either the male or female was parasitized. These results not only provide the first synthetic, comparative, and quantitative summary of the strong deleterious effects of parasites on host reproductive fitness, but also reveal a consistent role for parasites in shaping the opportunity for selection. 

   more » « less
5. Local adaptation of both plant and pathogen: an arms‐race compromise in switchgrass rust

   https://doi.org/10.1111/nph.70313  

   VanWallendael, Acer; Wijewardana, Chathurika; Bonnette, Jason; Vormwald, Lisa; Fritschi, Felix_B; Boe, Arvid; Chambers, Shelly; Mitchell, Robert_B; Rouquette, Jr, Francis_M; Wu, Yanqi; et al (June 2025, New Phytologist)

   Summary In coevolving species, parasites locally adapt to host populations as hosts locally adapt to resist parasites. Parasites often outpace host local adaptation since they have rapid life cycles, but host diversity, the strength of selection, and external environmental influence can result in complex outcomes.To better understand local adaptation in host–parasite systems, we examined locally adapted switchgrass (Panicum virgatum), and its leaf rust pathogen (Puccinia novopanici) across a latitudinal range in North America. We grew switchgrass genotypes in 10 replicated multiyear common gardens, measuring rust severity from natural infection in a ‘host reciprocal transplant’ framework for testing local adaptation. We conducted genome‐wide association mapping to identify genetic loci associated with rust severity.Genetically differentiated rust populations were locally adapted to northern and southern switchgrass, despite host local adaptation to environmental conditions in the same regions. Rust resistance was polygenic, and distinct loci were associated with rust severity in the north and south. We narrowed a previously identified large‐effect quantitative trait locus for rust severity to a candidate YELLOW STRIPE‐LIKE gene and linked numerous other loci to defense‐related genes.Overall, our results suggest that both hosts and parasites can be simultaneously locally adapted, especially when parasites impose less selection than other environmental factors. 

   more » « less