More Like this

1. 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
2. The cost of travel: How dispersal ability limits local adaptation in host–parasite interactions

   https://doi.org/10.1111/jeb.13754  

   Johnson, Pieter; Calhoun, Dana M.; Moss, Wynne E.; McDevitt‐Galles, Travis; Riepe, Tawni B.; Hallas, Joshua M.; Parchman, Thomas L.; Feldman, Chris R.; Achatz, Tyler J.; Tkach, Vasyl V.; et al (December 2020, Journal of Evolutionary Biology)

   Abstract Classical theory suggests that parasites will exhibit higher fitness in sympatric relative to allopatric host populations (local adaptation). However, evidence for local adaptation in natural host–parasite systems is often equivocal, emphasizing the need for infection experiments conducted over realistic geographic scales and comparisons among species with varied life history traits. Here, we used infection experiments to test how two trematode (flatworm) species (Paralechriorchis syntomenteraandRibeiroia ondatrae) with differing dispersal abilities varied in the strength of local adaptation to their amphibian hosts. Both parasites have complex life cycles involving sequential transmission among aquatic snails, larval amphibians and vertebrate definitive hosts that control dispersal across the landscape. By experimentally pairing 26 host‐by‐parasite population infection combinations from across the western USA with analyses of host and parasite spatial genetic structure, we found that increasing geographic distance—and corresponding increases in host population genetic distance—reduced infection success forP. syntomentera, which is dispersed by snake definitive hosts. For the avian‐dispersedR. ondatrae, in contrast, the geographic distance between the parasite and host populations had no influence on infection success. Differences in local adaptation corresponded to parasite genetic structure; although populations ofP. syntomenteraexhibited ~10% mtDNA sequence divergence, those ofR. ondatraewere nearly identical (<0.5%), even across a 900 km range. Taken together, these results offer empirical evidence that high levels of dispersal can limit opportunities for parasites to adapt to local host populations. 

   more » « less
3. Predation shifts coevolution toward higher host contact rate and parasite virulence

   https://doi.org/10.1098/rspb.2021.2800  

   Walsman, Jason C.; Cressler, Clayton E. (July 2022, Proceedings of the Royal Society B: Biological Sciences)

   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. 

   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. Broad host use and frequent polyandry in the facultative dulotic species Formica aserva (Hymenoptera: Formicidae)

   https://doi.org/10.1093/aesa/saae020  

   Scarparo, Giulia; West, Mari; Brelsford, Alan; Purcell, Jessica; Knolhoff, ed., Lisa (August 2024, Annals of the Entomological Society of America)

   Abstract The study of social parasitism faces numerous challenges arising from the intricate and intranidal host–parasite interactions and the rarity of parasites compared to their free-living counterparts. As a result, our understanding of the ecology and evolution of most social parasites remains limited. Using whole-genome and reduced-representation sequence data, we conducted a study to fill knowledge gaps on host use, colony social structure, and population genetics of the facultative dulotic ant Formica aserva Forel. Our study reveals the remarkable ability of F. aserva to exploit at least 20 different host species across its wide geographic distribution. In some cases, one social parasite colony exploits multiple hosts simultaneously, suggesting a high degree of generalization even at a local spatial scale. Approximately 80% of the colonies were monogyne (with a single queen), with many exhibiting higher rates of polyandry compared to most Formica ants. Although we identified a supergene on chromosome 3, its association with colony structure remains uncertain due to the rarity of polygyny in our sample. Population genetic analyses reveal substantial geographic population structure, with the greatest divergence between California populations and those from the rest of the range. Mitochondrial population structure differs from structure inferred from the nuclear genome on a broad geographic scale, suggesting a possible role of adaptive introgression or genetic drift. This study provides valuable insights into the ecology and evolution of F. aserva, underscoring the need for further research to decipher the complexities of host interactions and the genetic mechanisms that regulate social structure. 

   more » « less