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opencc-zeroDec 2014View details →

Data from: Parting ways: Parasite release in nature leads to sex-specific evolution of defense

We evaluate the extent to which males and females evolve along similar or different trajectories in response to the same environmental shift. Specifically, we use replicate experimental introductions in nature to consider how release from a key parasite (Gyrodactylus) generates similar or different defense evolution in male versus female guppies (Poecilia reticulata). After 8-12 generations of evolution, guppies were collected from the ancestral (parasite still present) and derived (parasite now absent) populations and bred for two generations in the laboratory to control for non-genetic effects. These F2 guppies were then individually infected with Gyrodactylus and infection dynamics were monitored on each fish. We found that parasite release in nature led to sex-specific evolutionary responses: males did not show much evolution of resistance, whereas females showed the evolution of increased resistance. Given that male guppies in the ancestral population had greater resistance to Gyrodactylus than did females, evolution in the derived populations led to reduction of sexual dimorphism in resistance. We argue that previous selection for high resistance in males constrained (relative to females) further evolution of the trait. We advocate more experiments considering sex-specific evolutionary responses to environmental change.

opencc-zeroDec 2013View details →

Data from: Predators and patterns of within-host growth can mediate both among-host competition and the evolution of transmission potential of parasites

Parasite prevalence shows tremendous spatiotemporal variation. Theory indicates this variation might stem from life history characteristics of parasites and key ecological factors. Here, we illustrate how the interaction of an important predator and the schedule of 'transmission potential' of two parasites can explain parasite abundance. A field survey showed that a non-castrating fungus (Metschnikowia bicuspidata) commonly infected a dominant zooplankton host (Daphnia dentifera), while a castrating bacterial parasite (Pasteuria ramosa) was rare. This result seemed surprising given that the bacterium produces many more infectious propagules (spores) than the fungus upon host death. The fungus's dominance can be explained by the schedule of within host growth of parasites (i.e., how transmission potential changes over the course of infection) and spore release from 'sloppy predators' (Chaoborus spp., who consume Daphnia prey whole, then later regurgitate the carapace and parasite spores). In essence, sloppy predators create a niche that the faster-schedule fungus currently occupies. However, a selection experiment showed the slower-schedule bacterium can evolve into this faster-schedule, predator-mediated niche (but pays a cost in maximal spore yield to do so). Hence, our study shows how parasite life history can interact with predation to strongly influence the ecology, epidemiology, and evolution of infectious disease. 18 pages, 1 table, 5 figures; Appendix

opencc-zeroDec 2016View details →

Data from: Integrating phylogenomic and population genomic patterns in avian lice provides a more complete picture of parasite evolution

Parasite diversity accounts for most of the biodiversity on earth, and is shaped by many processes (e.g. cospeciation, host-switching). To identify the effects of the processes that shape parasite diversity, it is ideal to incorporate both deep (phylogenetic) and shallow (population) perspectives. To this end, we developed a novel workflow to obtain phylogenetic and population genetic data from whole genome sequences of body lice parasitizing New World ground-doves. Phylogenies from these data showed consistent, highly resolved species-level relationships for the lice. By comparing the louse and ground-dove phylogenies, we found that over long-term evolutionary scales their phylogenies were largely congruent. Many louse lineages (both species and populations) also demonstrated high host-specificity, suggesting ground-dove divergence is a primary driver of their parasites' diversity. However, the few louse taxa that are generalists are structured according to biogeography at the population level. This suggests dispersal among sympatric hosts has some effect on body louse diversity, but over deeper time scales the parasites eventually sort according to host species. Overall, our results demonstrate that multiple factors explain the patterns of diversity in this group of parasites, and that the effects of these factors can vary over different evolutionary scales. The integrative approach we employed was crucial for uncovering these patterns, and should be broadly applicable to other studies.

opencc-zeroJul 2019View details →

Data from: How parasite interaction strategies alter virulence evolution in multi-parasite communities

The majority of organisms host multiple parasite species, each of which can interact with hosts and competitors through a diverse range of direct and indirect mechanisms. These within-host interactions can directly alter the mortality rate of coinfected hosts and alter the evolution of virulence (parasite induced host mortality). Yet we still know little about how within-host interactions affect the evolution of parasite virulence in multi-parasite communities. Here, we modeled the virulence evolution of two coinfecting parasites in a host population in which parasites interacted through cross immunity, immune suppression, immunopathology, or spite. We show (1) that these within-host interactions have different effects on virulence evolution when all parasites interact with each other in the same way vs. when coinfecting parasites have unique interaction strategies, (2) that all of these interactions cause the evolution of lower virulence in some hosts, and higher virulence in other hosts, depending on the hosts infection status, and (3) that for cross immunity and spite, whether parasites increased or decreased the evolutionarily stable virulence in coinfected hosts depended on interaction strength. These results improve our understanding of virulence evolution in complex parasite communities, and show that virulence evolution must be understood at the community scale.

opencc-zeroDec 2016View details →

Data from: Abiotic environmental variation drives virulence evolution in a fish host-parasite geographic mosaic

1.Parasite virulence varies greatly. Theory predicts that this arises from parasites optimising a trade-off between the mortality they inflict on current hosts, and their transmission to future hosts. The effect of the environment on this coevolution is rarely considered. 2.Geographic mosaics are fertile systems for studying coevolution, but again, the diversity of outcomes is often assumed to result from co-evolutionary dynamism, rather than being moulded by the environment. 3.Here we quantify variation in virulence among lakes in a geographic mosaic of coevolution between a trematode ectoparasite (Gyrodactylus arcuatus) and its three-spined stickleback (Gasterosteus aculeatus) host. 4.Virulence varies greatly in this system, and parasites are generally locally adapted to their hosts. 5.Parasites are also locally adapted to the water in their own lake, and virulence is strongly related to lake pH, the dominant axis of abiotic environmental variation in this system. 6.These results suggest that the evolution of virulence can be substantially affected by the abiotic environment, which has important implications for understanding coevolution. There are also implications for the evolutionary management of disease e.g. ectoparasites in aquaculture, the impacts of which might be expected to reduce given ongoing acidification of aquatic ecosystems.

opencc-zeroDec 2016View details →

Data from: The evolution of clutch size in hosts of avian brood parasites

Coevolution with avian brood parasites shapes a range of traits in their hosts, including morphology, behavior, and breeding systems. Here we explore whether brood parasitism is also associated with the evolution of host clutch size. Several studies have proposed that hosts of highly virulent parasites could decrease the costs of parasitism by evolving a smaller clutch size, because hosts with smaller clutches will lose fewer progeny when their clutch is parasitized. We describe a model of the evolution of clutch size, which challenges this logic and shows instead that an increase in clutch size (or no change) should evolve in hosts. We test this prediction using a broad-scale comparative analysis to ask whether there are differences in clutch size within hosts and between hosts and nonhosts. Consistent with our model, this analysis revealed that host species do not have smaller clutches and that hosts that incur larger costs from raising a parasite lay larger clutches. We suggest that brood parasitism might be an influential factor in clutch-size evolution and could potentially select for the evolution of larger clutches in host species.

opencc-zeroDec 2010View details →

Data from: The geographic structure of selection on a coevolving interaction between social parasitic wasps and their hosts hampers social evolution

Social parasites exploit societies, rather than organisms, and rear their brood in social insect colonies at the expense of their hosts, triggering a coevolutionary process that may affect host social structure. The resulting coevolutionary trajectories may be further altered by selection imposed by predators, which exploit the abundant resources concentrated in these nests. Here, we show that geographic differences in selection imposed by predators affects the structure of selection on coevolving hosts and their social parasites. In a multi-year study, we monitored the fate of the annual breeding attempts of the solitary-founding females of Polistes biglumis social wasps in four geographically distinct populations that varied in levels of attack by the congeneric social parasite, P. atrimandibularis. Foundress fitness depended mostly on whether, during the long founding phase, a colony was invaded by social parasites or attacked by predators. Foundresses from each population differed in morphological traits and reproductive tactics that were consistent with selection imposed by their natural enemies and in ways that may affect host sociality. In turn, parasite traits were consistent with selection imposed locally by hosts, implying a geographic mosaic of coevolution in this brood parasitic interaction.

FIGURES 11–16 in Macrobothriotaenia ficta (Cestoda: Proteocephalidea), a parasite of sunbeam snake (Xenopeltis unicolor): example of convergent evolution

FIGURES 11–16. Macrobothriotaenia ficta (Meggitt, 1931) from Xenopeltis unicolor. 11–13. Flattened scolex of mounted specimens (11, 12. adult specimen. 13. juvenile specimen, Vietnam, MHNG-PLAT 45476). 14, 15. Mature and pregravid proglottides, respectively, dorsal view, Thailand (BMNH 1976.4.13.14–15). 16. Gravid proglottis, ventral view, Vietnam (MHNG-PLAT 75454). Abbreviations: dc—dorsal osmoregulatory canals; vc—ventral osmoregulatory canals.

FIGURE 22 in Macrobothriotaenia ficta (Cestoda: Proteocephalidea), a parasite of sunbeam snake (Xenopeltis unicolor): example of convergent evolution

FIGURE 22. Macrobothriotaenia ficta (Meggitt, 1931) from Xenopeltis unicolor. Unmounted scolex, apical view (left) and view from lower side (right), Vietnam (MHNG-PLAT 75454).

FIGURES 17–21 in Macrobothriotaenia ficta (Cestoda: Proteocephalidea), a parasite of sunbeam snake (Xenopeltis unicolor): example of convergent evolution

FIGURES 17–21. Macrobothriotaenia ficta (Meggitt, 1931) from Xenopeltis unicolor. 17–19. Cross-sections of mature (17) and pregravid (18, 19) proglottides at level of anterior part (17, 18), and at level of ovary (19). 20. Terminal genitalia, ventral view, Thailand (BMNH 1976.4.13.14–15). 21. Eggs in distilled water, with collapsed outer hyaline envelope, Vietnam (MHNG-PLAT-75454). Abbreviations: dc—dorsal osmoregulatory canals; vc—ventral osmoregulatory canals.

FIGURES 1–10 in Macrobothriotaenia ficta (Cestoda: Proteocephalidea), a parasite of sunbeam snake (Xenopeltis unicolor): example of convergent evolution

FIGURES 1–10. Macrobothriotaenia ficta (Meggitt, 1931) from Xenopeltis unicolor. Scanning electron micrographs. 1. Scolex, apical view. 2. Scolex, lateral view. 3. Detail of a sucker, apical view. 4. Lower part of the exterior surface of a sucker. 5. Capilliform filitriches at level of the apex surface. 6. Capilliform filitriches at the upper marginal surface of a sucker. 7. Luminal surface of suckers covered with capilliform filitriches and few gladiate spinitriches. 8. Non-adherent surface of suckers covered with long capilliform filitriches and few gladiate spinitriches. 9, 10. Posterior part of suckers and proliferation zone covered with long gladiate spinitriches. Note: small black numbers correspond to the figures showing higher magnification images of these surfaces.

Fig. 16–18 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

Fig. 16–18. Pseudomyrmex elongatulus group, workers, full-face dorsal view of head (a) and lateral profile of body (b). 16, P. nimbus, holotype, Costa Rica (CASENT0863541); 17, P. salvini, syntype, Mexico (CASENT0902879); 18, P. veracruzensis, holotype, Mexico (CASENT0863542). Images from AntWeb (www. antweb.org); photographers Phil Ward (16, 18), Zach (Ziv) Lieberman (17).

Fig. 3 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

Fig. 3. Bivariate plots of measurements and indices concerned with eye size and petiole shape, in workers of P. apache (n = 17) and P. arcanus (n = 17). (a) PL/ LHT (petiole length/metatibia length) by HW (head width); (b) REL2 (eye length/head width) by PLI (petiole height/petiole length).

Fig. 13–15 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

Fig. 13–15. Pseudomyrmex elongatulus group, workers, full-face dorsal view of head (a), and lateral profile of body (b). 13, P. capillatus, holotype, Mexico (CASENT0863535); 14, P. exoratus, holotype worker, Mexico (CASENT0863539); 15, P. fasciatus, holotype, Costa Rica (CASENT0863540). Images from AntWeb (www.antweb.org); photographer Phil Ward.

Fig. 19–26 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

Fig. 19–26. Pseudomyrmex elongatulus group: distribution maps. 19, P. apache; 20, P. arcanus (circles), P. fasciatus (triangles); 21, P. championi; 22, P. capillatus (triangles), P. cognatus (circles); 23, P. elongatulus (circles), probable introduced populations (stars); 24, P. comitator (square), P. ereptor (triangle), P. exoratus (circles); 25, P. salvini; 26, P. nimbus (circles), P. veracruzensis (triangle).

Fig. 16–18 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

Fig. 3 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

Fig. 19–26 in Species Paraphyly and Social Parasitism: Phylogenomics, Morphology, and Geography Clarify the Evolution of the Pseudomyrmex elongatulus Group (Hymenoptera:

opencc-zeroSep 2021View details →

Parasite intensity and the evolution of migratory behavior

Migration can allow individuals to escape parasite infection, which can lead to a lower infection probability (prevalence) in a population and/or fewer parasites per individual (intensity). Since individuals with more parasites often have lower survival and/or fecundity, infection intensity shapes the life-history tradeoffs determining when migration is favored as a strategy to escape infection. Yet, most theory relies on susceptible-infected (SI) modeling frameworks, defining individuals as either healthy or infected, ignoring details of infection intensity. Here we develop a novel modeling approach that captures infection intensity as a spectrum, and ask under what conditions migration evolves as function of how infection intensity changes over time. We show that the relative timescales of migration and infection accumulation determine when migration is favored. We also find that population-level heterogeneity in infection intensity can lead to partial migration, where less-infected individuals migrate while more infected individuals remain resident. Our model is one of the first to consider how infection intensity can lead to migration. Our results frame migratory escape in light of infection intensity, rather than prevalence, thus demonstrating that decreased infection intensity should be considered a benefit of migration, alongside other typical drivers of migration.