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Interview with Kayla King, who studies the evolution and ecology of host-parasite interactions at the University of Oxford., (Copyright © 2022.)

Why do infectious diseases erupt in some host populations and not others? This question has spawned independent fields of research in evolution, ecology, public health, agriculture, and conservation. In the search for environmental and genetic factors that predict variation in parasitism, one hypothesis stands out for its generality and longevity: genetically homogeneous host populations are more likely to experience severe parasitism than genetically diverse populations. In this perspective piece, I draw on overlapping ideas from evolutionary biology, agriculture, and conservation to capture the far-reaching implications of the link between genetic diversity and disease. I first summarize the development of this hypothesis and the results of experimental tests. Given the convincing support for the protective effect of genetic diversity, I then address the following questions: (1) Where has this idea been put to use, in a basic and applied sense, and how can we better use genetic diversity to limit disease spread? (2) What new hypotheses does the established disease-diversity relationship compel us to test? I conclude that monitoring, preserving, and augmenting genetic diversity is one of our most promising evolutionarily informed strategies for buffering wild, domesticated, and human populations against future outbreaks., (© 2021 The Authors. Evolution © 2021 The Society for the Study of Evolution.)

When facing an emerging infectious disease of conservation concern, we often have little information on the nature of the host-parasite interaction to inform management decisions. However, it is becoming increasingly clear that the life-history strategies of host species can be predictive of individual- and population-level responses to infectious disease, even without detailed knowledge on the specifics of the host-parasite interaction. Here, we argue that a deeper integration of life-history theory into disease ecology is timely and necessary to improve our capacity to understand, predict and mitigate the impact of endemic and emerging infectious diseases in wild populations. Using wild vertebrates as an example, we show that host life-history characteristics influence host responses to parasitism at different levels of organisation, from individuals to communities. We also highlight knowledge gaps and future directions for the study of life-history and host responses to parasitism. We conclude by illustrating how this theoretical insight can inform the monitoring and control of infectious diseases in wildlife., (© 2021 John Wiley & Sons Ltd.)

OBJECTIVE. Many models have been used to understand radiology practice, including economics, engineering, and information technology. Each has advantages, but each also has drawbacks, failing to illuminate important aspects of radiologists' work. A model that offers additional insights is ecology. CONCLUSION. By looking at radiology practice through the ecologic concept of symbiosis, radiologists can gain new understanding and appreciation of aspects of their work that can render it more fruitful and sustainable.

Parasites are ubiquitous components of biological systems that have evolved in multiple independent lineages during the history of life, resulting in a diversity of taxa greater than that of their free-living counterparts. Extant host-parasite associations are the result of tight reciprocal adaptations that allow parasites to exploit specific biological features of their hosts to ensure their transmission, survival, and maintenance of viable populations. As a result, parasites may affect host physiology, morphology, reproduction or behaviour, and they are increasingly recognized as having significant impacts on host individuals, populations, communities and even ecosystems. Although this is usually acknowledged by parasite ecologists, fish ecologists often ignore parasitism in their studies, often acting as though their systems are free of parasites. However, the effects of parasites on their hosts can alter variables routinely used in fish ecology, ranging from the level of individual fish (e.g. condition factors) to populations (e.g. estimates of mortality and reproductive success) or communities (e.g. measures of interspecific competition or the structure and functioning of food webs). By affecting fish physiology, parasites can also interfere with measurements of trophic levels by means of stable isotope composition, or have antagonistic or synergistic effects with host parameters normally used as indicators of different sources of pollution. Changes in host behaviour induced by parasites can also modify host distribution patterns, habitat selection, diet composition, sexual behaviour, etc., with implications for the ecology of fish and of their predators and prey. In this review, we summarise and illustrate the likely biases and erroneous conclusions that one may expect from studies of fish ecology that ignore parasites, from the individual to the community level. Given the impact of parasites across all levels of biological organisation, we show that their omission from the design and analyses of ecological studies poses real risks of flawed interpretations for those patterns and processes that ecologists seek to uncover., (Copyright © 2020 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

The impacts of parasites on hosts and the role that parasites play in ecosystems must be underlain by the load of parasites in individual hosts. To help explain and predict parasite load across a broad range of species, quantitative theory has been developed based on fundamental relationships between organism size, temperature and metabolic rate. Here, we elaborate on an aspect of that 'scaling theory for parasitism', and test a previously unexplored prediction, using new data for total ectoparasite load from 263 wild birds of 42 species. We reveal that, despite the expected substantial variation in parasite load among individual hosts, (i) the theory successfully predicts the distinct increase of ectoparasite load with host body size, indicating the importance of geometric scaling constraints on access to host resources, (ii) ectoparasite load appears ultimately limited by access-not to host space-but to host energy, and (iii) there is a currency-dependent shift in taxonomic dominance of parasite load on larger birds. Hence, these results reveal a seemingly new macroecological pattern, underscore the utility of energy flux as a currency for parasitism and highlight the promise of using scaling theory to provide baseline expectations for parasite load for a diversity of host species.

Locating and counting parasites on a host is a fundamental aspect of ecological research and basic veterinary and clinical practice. Variability in the biology and behavior of both hosts and parasites creates many methodological, logistical, and ethical considerations that must be made to collect this deceptively simple measurement. We identified methods that are used to count ticks (Acari: Ixodida, Leach 1815) on hosts by reviewing the methods sections of relevant published studies. Unfortunately, there is no best method agreed upon by scientists to collect ticks from hosts. In general, we suggest that studies focusing purely on counting ticks on hosts should use more sensitive methods to determine patterns of tick distribution on the surfaces of unconscious or deceased hosts in order to provide host body regions to target in future studies to maximize tick detection ability and limit the costs of research for researchers and the host animals involved. As ticks are counted on hosts for many different reasons, researchers must be goal oriented and chose methods that are appropriate for addressing their specific aims., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Covering: January 2015 through December 2017 This review focuses on recent studies on the chemical ecology of planktonic marine ecosystems, with the objective of presenting a comprehensive overview of new findings in the field in the time period covered. In order to highlight the role of chemically mediated interactions in the marine plankton this review has been organized by ecological concepts starting with intraspecific communication, followed by interspecific interactions (including facilitation and mutualism, host-parasite, allelopathy, and predator-prey), and finally the effects of plankton secondary metabolites on community and ecosystem-wide interactions.

Identifying the ecological factors that shape parasite distributions remains a central goal in disease ecology. These factors include dispersal capability, environmental filters and geographic distance. Using 520 haemosporidian parasite genetic lineages recovered from 7,534 birds sampled across tropical and temperate South America, we tested (a) the latitudinal diversity gradient hypothesis and (b) the distance-decay relationship (decreasing proportion of shared species between communities with increasing geographic distance) for this host-parasite system. We then inferred the biogeographic processes influencing the diversity and distributions of this cosmopolitan group of parasites across South America. We found support for a latitudinal gradient in diversity for avian haemosporidian parasites, potentially mediated through higher avian host diversity towards the equator. Parasite similarity was correlated with climate similarity, geographic distance and host composition. Local diversification in Amazonian lineages followed by dispersal was the most frequent biogeographic events reconstructed for haemosporidian parasites. Combining macroecological patterns and biogeographic processes, our study reveals that haemosporidian parasites are capable of circumventing geographic barriers and dispersing across biomes, although constrained by environmental filtering. The contemporary diversity and distributions of haemosporidian parasites are mainly driven by historical (speciation) and ecological (dispersal) processes, whereas the parasite community assembly is largely governed by host composition and to a lesser extent by environmental conditions., (© 2019 John Wiley & Sons Ltd.)

In recent decades, parasite community ecology has produced hundreds of studies on an ever-growing number of host species, and developed into an active sub-discipline of parasitology. However, this growth has been characterized by a lack of standards in the practices used by researchers, with many common approaches being flawed, unjustified or misleading. Here, in the hope of promoting advances in the study of parasite community ecology, I identify some of the most common errors or weaknesses in past studies, and propose ten simple rules for best practice in the field. They cover issues including, among others, taxonomic resolution, proper and justifiable analytical methods, higher-level replication, controlling for sampling effort or species richness, accounting for spatial distances, using experimental approaches, and placing raw data in the public domain. While knowledge of parasite communities has expanded in breadth, with more and more host species being studied, true progress has been very limited with respect to our understanding of fundamental general processes shaping these communities. It is hoped that the guidelines presented here can direct researchers away from the entrenched use of certain approaches flawed in design, analysis or interpretation, by offering a more rigorous and standardized set of practices, and, hopefully, a way forward.

Russia, both as the USSR and the Russian federation, provided a source of parasitological theory for decades. A key figure in Russian parasitology was Yevgeny Pavlovsky. He developed the nidus concept of Pavlovsky provided the conceptual basis for the field of pathoecology. He also coined the term "Paleoparasitology". Pathoecology is a foundation concept in archaeological parasitology. Paleoparasitology, as defined by Pavlovsky, is an avenue for understanding of host parasite evolution over very long time periods. These contributions are not fully recognized internationally. Similarly, the long history of Russian paleontological and archaeological investigations are not fully known. Most recently, discoveries from archaeological sites show that a pattern of zoonotic infection prevailed among archaeological populations in central Russia. This included a case of apparent host switching of beef tapeworm infection to reindeer. This latter discovery raises the possibility that archaeological parasitology can contribute to the new Stockholm Paradigm of ecological fitting, host switching, and emergent disease. This review covers all of the parasitological discoveries from ancient Russia and illustrates how Russian models and discoveries defined parasitological theory in the past and present., (Copyright © 2018 Elsevier Inc. All rights reserved.)

There have been considerable advances in our understanding of the systematics and ecology of Opisthorchis viverrini; however, this new knowledge has not only clarified but also complicated the situation. We now know that what was once considered to be a single species is, in fact, a species complex, with the individual species being confined to specific wetland areas. There is also a strong genetic association between the members of the O. viverrini species complex and their Bithynia snail intermediate hosts. Although this does not negate data collected before the recognition of this situation, it does lead to the caveat that regional and temporal variations in data collected may be related to the species examined. The advances in ecology have generally been spatially limited and have led, in part, to contradictory results that may well be related to nonrecognition of the species studied. It may also be related to natural temporal and spatial variation related, for example, to habitat characteristics. To understand the variation present, it will be necessary to conduct long-term (several years at least) sampling projects after defining the genetic characteristics of O. viverrini sensu lato and its Bithynia snail intermediate hosts., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A pressing challenge for ecologists is predicting how human-driven environmental changes will affect the complex pattern of interactions among species in a community. Weighted networks are an important tool for studying changes in interspecific interactions because they record interaction frequencies in addition to presence or absence at a field site. Here we show that changes in weighted network structure following habitat modification are, in principle, predictable. Our approach combines field data with mathematical models: the models separate changes in relative species abundance from changes in interaction preferences (which describe how interaction frequencies deviate from random encounters). The models with the best predictive ability compared to data requirement are those that capture systematic changes in interaction preferences between different habitat types. Our results suggest a viable approach for predicting the consequences of rapid environmental change for the structure of complex ecological networks, even in the absence of detailed, system-specific empirical data.In a changing world, the ability to predict the impact of environmental change on ecological communities is essential. Here, the authors show that by separating species abundances from interaction preferences, they can predict the effects of habitat modification on the structure of weighted species interaction networks, even with limited data.

Few hosts have many parasites while many hosts have few parasites. This axiom of macroparasite aggregation is so pervasive it is considered a general law in disease ecology, with important implications for the dynamics of host-parasite systems. Because of these dynamical implications, a significant amount of work has explored both the various mechanisms leading to parasite aggregation patterns and how to infer mechanism from these patterns. However, as many disease mechanisms can produce similar aggregation patterns, it is not clear whether aggregation itself provides any additional information about mechanism. Here we apply a "constraint-based" approach developed in macroecology that allows us to explore whether parasite aggregation contains any additional information beyond what is provided by mean parasite load. We tested two constraint-based null models, both of which were constrained on the total number of parasites P and hosts H found in a sample, using data from 842 observed amphibian host-trematode parasite distributions. We found that constraint-based models captured ~85% of the observed variation in host-parasite distributions, suggesting that the constraints P and H contain much of the information about the shape of the host-parasite distribution. However, we also found that extending the constraint-based null models can identify the potential role of known aggregating mechanisms (such as host heterogeneity) and disaggregating mechanisms (such as parasite-induced host mortality) in constraining host-parasite distributions. Thus, by providing robust null models, constraint-based approaches can help guide investigations aimed at detecting biological processes that directly affect parasite aggregation above and beyond those that indirectly affect aggregation through P and H., (© 2016 by the Ecological Society of America.)

Premise of Study: The factors driving variation in species interactions are often unknown, and few studies have made a link between changes in interactions and the strength of selection., Methods: We report on spatial variation in functional responses by a seed predator (SP) and its parasitic wasps associated with the herb Ruellia nudiflora . We assessed the influence of plant density on consumer responses and determined whether density effects and spatial variation in functional responses altered natural selection by these consumers on the plant. We established common gardens at two sites in Yucatan, Mexico, and planted R. nudiflora at two densities in each garden. We recorded fruit output and SP and parasitoid attack; calculated relative fitness (seed number) under scenarios of three trophic levels (accounting for SP and parasitoid effects), two trophic levels (accounting for SP but not parasitoid effects), and one trophic level (no consumer effects); and compared selection strength on fruit number under these scenarios across sites and densities., Key Results: There was spatial variation in SP recruitment, whereby the SP functional response was negatively density-dependent at one site but density-independent at the other; parasitoid responses were density-independent and invariant across sites. Site variation in SP attack led, in turn, to differences in SP selection on fruit output, and parasitoids did not alter SP selection. There were no significant effects of density at either site., Conclusions: Our results provide a link between consumer functional responses and consumer selection on plants, which deepens our understanding of geographic variation in the evolutionary outcomes of multitrophic interactions., (© 2017 Botanical Society of America.)

When parasites have different interests in regard to how their host should behave this can result in a conflict over host manipulation, i.e. parasite induced changes in host behaviour that enhance parasite fitness. Such a conflict can result in the alteration, or even complete suppression, of one parasite's host manipulation. Many parasites, and probably also symbionts and commensals, have the ability to manipulate the behaviour of their host. Non-manipulating parasites should also have an interest in host behaviour. Given the frequency of multiple parasite infections in nature, potential conflicts of interest over host behaviour and manipulation may be common. This review summarizes the evidence on how parasites can alter other parasite's host manipulation. Host manipulation can have important ecological and medical consequences. I speculate on how a conflict over host manipulation could alter these consequences and potentially offer a new avenue of research to ameliorate harmful consequences of host manipulation., (© 2016 The Authors BioEssays Published by WILEY Periodicals, Inc.)

How should we model evolution in spatially structured populations? Here, I review an evolutionary ecology approach based on the technique of spatial moment equations. I first provide a mathematical underpinning to the derivation of equations for the densities of various spatial configurations in network-based models. I then show how this spatial ecological framework can be coupled with an adaptive dynamics approach to compute the invasion fitness of a rare mutant in a resident population at equilibrium. Under the additional assumption that mutations have small phenotypic effects, I show that the selection gradient can be expressed as a function of neutral measures of genetic and demographic structure. I discuss the connections between this approach and inclusive fitness theory, as well as the applicability and limits of this technique. My main message is that spatial moment equations can be used as a means to obtain compact qualitative arguments about the evolution of life-history traits for a variety of life cycles., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Complex ecological networks appear robust to primary extinctions, possibly due to consumers' tendency to specialize on dependable (available and persistent) resources. However, modifications to the conditions under which the network has evolved might alter resource dependability. Here, we ask whether adaptation to historical conditions can increase community robustness, and whether such robustness can protect communities from collapse when conditions change. Using artificial life simulations, we first evolved digital consumer-resource networks that we subsequently subjected to rapid environmental change. We then investigated how empirical host-parasite networks would respond to historical, random and expected extinction sequences. In both the cases, networks were far more robust to historical conditions than new ones, suggesting that new environmental challenges, as expected under global change, might collapse otherwise robust natural ecosystems.

The interest of F. Macfarlane Burnet in host-parasite interactions grew through the 1920s and 1930s, culminating in his book, Biological Aspects of Infectious Disease (1940), often regarded as the founding text of disease ecology. Our knowledge of the influences on Burnet's ecological thinking is still incomplete. Burnet later attributed much of his conceptual development to his reading of British theoretical biology, especially the work of Julian Huxley and Charles Elton, and regretted he did not study Theobald Smith's Parasitism and Disease (1934) until after he had formulated his ideas. Scholars also have adduced Burnet's fascination with natural history and the clinical and public health demands on his research effort, among other influences. I want to consider here additional contributions to Burnet's ecological thinking, focusing on his intellectual milieu, placing his research in a settler society with exceptional expertise in environmental studies and pest management. In part, an ''ecological turn'' in Australian science in the 1930s, derived to a degree from British colonial scientific investments, shaped Burnet's conceptual development. This raises the question of whether we might characterize, in postcolonial fashion, disease ecology, and other studies of parasitism, as successful settler colonial or dominion science.

This paper reports on an entomological survey performed over the period 2009-2011 in endemic focus of peri-urban TOSV in South of France located from 24km east of Marseille. Sand flies were captured using CDC light traps set in sand fly resting places overnight, and temperature, relative humidity and wind were recorded to establish possible relations between meteorological factors and vector densities. The most common species, of 5,432 specimens collected and identified, was Phlebotomus perniciosus (74%), followed by Sergentomyia minuta (6%) and Phlebotomus ariasi (1%). Male flies were highly predominant for all Larroussius species instead of S. minuta which counted (85%) of females. The results shed light on the wide population's dynamic of P. perniciosus in France showing a diphasic seasonal trend with two abundance peaks at the beginning of July and late August, when a mean temperature is from 23.3 to 25.7°C. Interestingly, these two peaks are corresponding to the peaks of occurrence of human TOSV cases. Among the 1724 females collected, 549 (32%) were blood-fed. Based on the results of blood meal analyses, P. perniciosus fed on large animal's diversity (man, chicken, rabbit, others mammalians, etc.), including bats that are the only species found naturally infected by TOSV. Results indicate that host choice was probably related to its availability than specific attractiveness. Data presented confirm that sand flies easily adapted to the periurban sites like, P. perniciosus may represent a public health concern for pathogen transmission in similar Mediterranean environments., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Many parasites alter the behaviour of their host to their own advantage, yet hosts often vary in their susceptibility to manipulation. The ecological and evolutionary implications of such variation can be profound, as resistant host populations may suffer lower parasite pressures than those susceptible to manipulation. To test this prediction, we assessed parasite-induced aggressive behaviours across 16 populations of two Temnothorax ant species, many of which harbour the slavemaker ant Protomognathus americanus. This social parasite uses its Dufour's gland secretions to manipulate its hosts into attacking nestmates, which may deter defenders away from itself during invasion. We indeed find that colonies that were manipulated into attacking their Dufour-treated nestmates were less aggressive towards the slavemaker than those that did not show slavemaker-induced nestmate attack. Slavemakers benefited from altering their hosts' aggression, as both the likelihood that slavemakers survived host encounters and slavemaker prevalence in ant communities increased with slavemaker-induced nestmate attack. Finally, we show that Temnothorax longispinosus colonies were more susceptible to manipulation than Temnothorax curvispinosus colonies. This explains why T. curvispinosus colonies responded with more aggression towards invading slavemakers, why they were less likely to let slavemakers escape and why they were less frequently parasitized by the slavemaker than T. longispinosus. Our findings highlight that large-scale geographic variation in resistance to manipulation can have important implications for the prevalence and host preference of parasites., (© 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.)

Despite the fact that parasites are highly specialized with respect to their hosts, empirical evidence demonstrates that host switching rather than co-speciation is the dominant factor influencing the diversification of host-parasite associations. Ecological fitting in sloppy fitness space has been proposed as a mechanism allowing ecological specialists to host-switch readily. That proposal is tested herein using an individual-based model of host switching. The model considers a parasite species exposed to multiple host resources. Through time host range expansion can occur readily without the prior evolution of novel genetic capacities. It also produces non-linear variation in the size of the fitness space. The capacity for host colonization is strongly influenced by propagule pressure early in the process and by the size of the fitness space later. The simulations suggest that co-adaptation may be initiated by the temporary loss of less fit phenotypes. Further, parasites can persist for extended periods in sub-optimal hosts, and thus may colonize distantly related hosts by a "stepping-stone" process.

The presence of trematodes with a free-living metacercarial stage is a common feature of most habitats and includes important species such as Fasciola hepatica, Parorchis acanthus and Zygocotyle lunata. These trematodes encyst on the surface of an animal or plant that can act as a transport host, which form the diet of the target definitive host. Although these species are often considered individually, they display common characteristics in their free-living biology indicating a shared transmission strategy, yet in comparison to species with penetrative cercariae this aspect of their life cycles remains much overlooked. This review integrates the diverse data and presents a novel synthesis of free-living metacercariae using epibiosis as the basis of a new framework to describe the relationship between transport hosts and parasites. All aspects of their biology during the period that they are metabolically independent of a host are considered, from cercarial emergence to metacercarial excystment., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The three-spined stickleback is a small teleost fish, native to coastal regions of the Northern Hemisphere, which has emerged as a key model organism in evolutionary biology and ecology. Sticklebacks possess a well-documented and experimentally amenable parasite fauna, and are well suited to both laboratory and field parasitological investigation. As a consequence, sticklebacks have been extensively used as model hosts in studies of host-parasite interactions, and these studies have provided considerable insight into the roles of parasites in ecology and evolutionary biology. In this review, I discuss key advances in our understanding of host-parasite interactions that have arisen from studies involving stickleback hosts, highlight areas of current research activity, and identify potentially promising areas for future research., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Legionella pneumophila is an aquatic organism that interacts with amoebae and ciliated protozoa as the natural hosts, and this interaction plays a central role in bacterial ecology and infectivity. Upon transmission to humans, L. pneumophila infect and replicate within alveolar macrophages causing pneumonia. Intracellular proliferation of L. pneumophila within the two evolutionarily distant hosts is facilitated by bacterial exploitation of evolutionarily conserved host processes that are targeted by bacterial protein effectors injected into the host cell by the Dot/Icm type VIB translocation system. Although cysteine is semi-essential for humans and essential for amoeba, it is a metabolically favorable source of carbon and energy generation by L. pneumophila. To counteract host limitation of cysteine, L. pneumophila utilizes the AnkB Dot/Icm-translocated F-box effector to promote host proteasomal degradation of polyubiquitinated proteins within amoebae and human cells. Evidence indicates ankB and other Dot/Icm-translocated effector genes have been acquired through inter-kingdom horizontal gene transfer.

"It is hard to realize that the living world as we know it is just one among many possibilities" [1]. Evolving digital ecological networks are webs of interacting, self-replicating, and evolving computer programs (i.e., digital organisms) that experience the same major ecological interactions as biological organisms (e.g., competition, predation, parasitism, and mutualism). Despite being computational, these programs evolve quickly in an open-ended way, and starting from only one or two ancestral organisms, the formation of ecological networks can be observed in real-time by tracking interactions between the constantly evolving organism phenotypes. These phenotypes may be defined by combinations of logical computations (hereafter tasks) that digital organisms perform and by expressed behaviors that have evolved. The types and outcomes of interactions between phenotypes are determined by task overlap for logic-defined phenotypes and by responses to encounters in the case of behavioral phenotypes. Biologists use these evolving networks to study active and fundamental topics within evolutionary ecology (e.g., the extent to which the architecture of multispecies networks shape coevolutionary outcomes, and the processes involved).

Infectious disease plays a major role in the lives of wild primates, and the past decade has witnessed significant strides in our understanding of primate disease ecology. In this review, I briefly describe some key findings from phylogenetic comparative approaches, focusing on analyses of parasite richness that use the Global Mammal Parasite Database. While these studies have provided new answers to fundamental questions, new questions have arisen, including questions about the underlying epidemiological mechanisms that produce the broader phylogenetic patterns. I discuss two examples in which theoretical models have given us new traction on these comparative questions. First, drawing on findings of a positive association between range use intensity and the richness of helminth parasites, we developed a spatially explicit agent-based model to investigate the underlying drivers of this pattern. From this model, we are gaining deeper understanding of how range use intensity results in greater exposure to parasites, thus producing higher prevalence in the simulated populations-and, plausibly, higher parasite richness in comparative analyses. Second, I show how a model of disease spread on social networks provides solid theoretical foundations for understanding the effects of sociality and group size on parasitism across primate species. This study further revealed that larger social groups are more subdivided, which should slow the spread of infectious diseases. This effect could offset the increased disease risk expected in larger social groups, which has yet to receive strong empirical support in our comparative analyses. In addition to these examples, I discuss the need for more meta-analyses of individual-level phenomena documented in the field, and for greater linkage between theoretical modeling and field research., (© 2012 Wiley Periodicals, Inc.)

Myxosporean parasites Cystodiscus axonis and C. australis are pathogens of native and exotic Australian frog species. The pathology and ecological outcomes of infection with these parasites were investigated in this study. Gliosis was correlated to Cystodiscus axonis plasmodia in the brains of (9/60) tadpoles and (3/9) adult endangered Green and golden bell frogs using ordinal regression. Severe host reactions to C. axonis (haemorrhage, necrosis, and vasulitis) were observed in the brains of threatened Southern bell frogs (8/8), critically endangered Booroolong frogs (15/44) and Yellow spotted bell frogs (3/3). Severe brain lesions were associated with behavioural changes, neurological dysfunction, and spontaneous death. Both C. axonis and C. australis develop in the bile ducts of tadpoles, the plasmodia were significantly associated with biliary hyperplasia, inflammation and the loss of hepatocytes in (34/72) Green and golden bell frog tadpoles using ordinal regression. These lesions were so severe that in some cases 70% of the total liver was diseased. Normal liver function in tadpoles is necessary for metamorphosis, metabolism, and immune function. We postulate that this extensive liver damage would have significant host health impacts. Severe hepatic myxosporidiosis was more prevalent in tadpoles examined in autumn and winter (overwintered), suggestive of delayed metamorphosis in infected tadpoles, which would have serious flow-on effects in small populations. We compared the sensitivity of histopathology and species-specific PCR in the detection of C. australis and C. axonis. PCR was determined to be the most sensitive method (detection limit 1 myxospore equivalent of ribosomal DNA). Histology, however, had the advantage of assessing the impact of the parasite on the host. It was concluded that these parasites have the potential for significant ecological impacts, because of their high prevalence of infection and their ability to cause disease in some frogs.

The structure of a parasite system is formed and its functioning takes place in qualitatively different environments. The aquatic environment serves as a source of new elements and modules, energy, and information for parasite systems. And the parasite systems, for their part, affect the physical and biological parameters of the environment. Many intestinal infections caused by pathogenic microorganisms generally characterized by an acute disease course are related to a water factor. Such are typhus, typhoids, dysentery, cholera, salmonellosis, virus hepatitis, and others. Many parasitic diseases caused by pathogenic intestinal protistae (lambliasis, amebiasis, balantidiasis), blood parasite protistae (malaria), helminthes (opisthorchiasis, fascioliasis, diphyllobothriasis, cercariosis, pseudoamphistomosis) are also closely related to a water factor. Ascaridiasis, hymenolepiasis, trichocephalosis, and echinococcosis have a less close but still self-evident relationship to a water factor. The clbse relationships of many parasitic diseases to a water factor are also determined by the fact that the life cycles of many parasites necessarily include various intermediate hosts and parasite vectors, such as fishes, mollusks, crustaceans, and insects, which are aquatic organisms at some stages of their life. The results of continuous exposure of people to parasitic diseases are quite similar to the suppressive effects of the environment in the ecologically troublesome regions. The most prognostically useful information is formed while mapping by medical and ecological regions, by employing a combination of current mathematical and cartographical methods. The former include cluster analysis, quartering method, informational logical analysis, which are all described in this article and others. Regional mapping using the parasitological criteria should achieve at least two goals: 1) a scientific one that aids in finding causative connections and to prognosticate a situation; 2) a practical one that assists in developing regional programs for disease control and prevention. It is necessary to use the recommendations described in detail in the article in order to have the maximum results during medical and ecological mapping by the regions with a future goal of obtaining useful prognostic information.

Many ecological studies use the analysis of count data to arrive at biologically meaningful inferences. Here, we introduce a hierarchical bayesian approach to count data. This approach has the advantage over traditional approaches in that it directly estimates the parameters of interest at both the individual-level and population-level, appropriately models uncertainty, and allows for comparisons among models, including those that exceed the complexity of many traditional approaches, such as ANOVA or non-parametric analogs. As an example, we apply this method to oviposition preference data for butterflies in the genus Lycaeides. Using this method, we estimate the parameters that describe preference for each population, compare the preference hierarchies among populations, and explore various models that group populations that share the same preference hierarchy.

The diversity of life is ultimately generated by evolution, and much attention has focused on the rapid evolution of ecological traits. Yet, the tendency for many ecological traits to instead remain similar over time [niche conservatism (NC)] has many consequences for the fundamental patterns and processes studied in ecology and conservation biology. Here, we describe the mounting evidence for the importance of NC to major topics in ecology (e.g. species richness, ecosystem function) and conservation (e.g. climate change, invasive species). We also review other areas where it may be important but has generally been overlooked, in both ecology (e.g. food webs, disease ecology, mutualistic interactions) and conservation (e.g. habitat modification). We summarize methods for testing for NC, and suggest that a commonly used and advocated method (involving a test for phylogenetic signal) is potentially problematic, and describe alternative approaches. We suggest that considering NC: (1) focuses attention on the within-species processes that cause traits to be conserved over time, (2) emphasizes connections between questions and research areas that are not obviously related (e.g. invasives, global warming, tropical richness), and (3) suggests new areas for research (e.g. why are some clades largely nocturnal? why do related species share diseases?)., (2010 Blackwell Publishing Ltd/CNRS.)

Many organisms, including entomopathogenous fungi, predators or parasites, use aphids as ressources. Parasites of aphids are mostly endoparasitoid insects, i.e. insects which lay eggs inside the body of an other insect which will die as a result of their development. In this article, we review the consequences of the numerous pecularities of aphid biology and ecology for their endoparasitoids, notably the Aphidiinae (Hymenoptera: Braconidae). We first examine the various mechanisms used by aphids for defence against these enemies. We then explore the strategies used by aphidiine parasitoids to exploit their aphid hosts. Finally, we consider the responses of both aphids and parasitoids to ecological constraints induced by seasonal cycles and to environmental variations linked to host plants and climate. The fundamental and applied interest of studying these organisms is discussed., (Copyright 2010 Académie des sciences. Published by Elsevier SAS. All rights reserved.)

There is great interest in the occurrence and consequences of interspecific interactions among co-infecting parasites. However, the extent to which interactions occur is unknown, because there are no validated methods for their detection. We developed a model that generated abundance data for two interacting macroparasite (e.g., helminth) species, and challenged the data with various approaches to determine whether they could detect the underlying interactions. Current approaches performed poorly - either suggesting there was no interaction when, in reality, there was a strong interaction occurring, or inferring the presence of an interaction when there was none. We suggest the novel application of a generalized linear mixed modelling (GLMM)-based approach, which we show to be more reliable than current approaches, even when infection rates of both parasites are correlated (e.g., via a shared transmission route). We suggest that the lack of clarity regarding the presence or absence of interactions in natural systems may be largely attributed to the unreliable nature of existing methods for detecting them. However, application of the GLMM approach may provide a more robust method of detection for these potentially important interspecific interactions from ecological data.

Many studies have examined the long-term effects of selective logging on the abundance and diversity of free-ranging primates. Logging is known to reduce the abundance of some primate species through associated hunting and the loss of food trees for frugivores; however, the potential role of pathogens in such primate population declines is largely unexplored. Selective logging results in a suite of alterations in host ecology and forest structure that may alter pathogen dynamics in resident wildlife populations. In addition, environmental pollution with human fecal material may present a risk for wildlife infections with zoonotic protozoa, such as Cryptosporidium and Giardia. To better understand this interplay, we compared patterns of infection with these potentially pathogenic protozoa in sympatric western lowland gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes troglodytes) in the undisturbed Goualougo Triangle of Nouabalé-Ndoki National Park and the adjacent previously logged Kabo Concession in northern Republic of Congo. No Cryptosporidium infections were detected in any of the apes examined and prevalence of infection with Giardia was low (3.73% overall) and did not differ between logged and undisturbed forest for chimpanzees or gorillas. These results provide a baseline for prevalence of these protozoa in forest-dwelling African apes and suggest that low-intensity logging may not result in long-term elevated prevalence of potentially pathogenic protozoa.

There is growing interest in the ecological consequences of fear, as evidenced by the numerous studies on the nonconsumptive, trait-mediated effects of predators. Parasitism, however, has yet to be fully integrated into research on the ecology of fear, despite it having direct negative and often lethal effects on hosts and being the most common life history strategy on the planet. This might at least be partly due to the traditional, but untested, assumption that anti-parasite responses are weak relative to anti-predator responses. To test this hypothesis, we quantified the activity and location responses of Bufo americanus tadpoles to one of six chemical cues: water; cercariae of Echinostoma trivolvis, a trematode which infects and can kill amphibians; a snail releasing E. trivolvis cercariae; an uninfected snail; food; or conspecific alarm chemicals signaling predation. There is also literature encouraging research on the context dependency and pollution-induced disruption of fear responses. Consequently, before quantifying responses to the chemical cues, half of the B. americanus were exposed to the herbicide atrazine (201 microg/l for 4 days), a reported inhibitor of fear responses in fish. Tadpoles were attracted to food, were indifferent to an uninfected snail, avoided alarm chemicals, and exhibited avoidance and elevated activity in response to a snail shedding cercariae and cercariae alone. Atrazine had no detectable effects on B. americanus' responses to the tested cues despite the use of a higher concentration and longer exposure duration than has been repeatedly shown to inhibit chemical cue detection in fish. The magnitude of anti-parasite and anti-predator responses were qualitatively similar, suggesting that the fear of disease and its ecological consequences could be comparable to that of predation. Consequently, we call for a greater integration of parasites into research on the ecology of fear and trait-mediated indirect effects.

The degree of phenotypic divergence and reproductive isolation between taxon pairs can vary quantitatively, and often increases as evolutionary divergence proceeds through various stages, from polymorphism to population differentiation, ecotype and race formation, speciation, and post-speciational divergence. Although divergent natural selection promotes divergence, it does not always result in strong differentiation. For example, divergent selection can fail to complete speciation, and distinct species pairs sometimes collapse ('speciation in reverse'). Widely-discussed explanations for this variability concern genetic architecture, and the geographic arrangement of populations. A less-explored possibility is that the degree of phenotypic and reproductive divergence between taxon pairs is positively related to the number of ecological niche dimensions (i.e., traits) subject to divergent selection. Some data supporting this idea stem from laboratory experimental evolution studies using Drosophila, but tests from nature are lacking. Here we report results from manipulative field experiments in natural populations of herbivorous Timema stick insects that are consistent with this 'niche dimensionality' hypothesis. In such insects, divergent selection between host plants might occur for cryptic colouration (camouflage to evade visual predation), physiology (to detoxify plant chemicals), or both of these niche dimensions. We show that divergent selection on the single niche dimension of cryptic colouration can result in ecotype formation and intermediate levels of phenotypic and reproductive divergence between populations feeding on different hosts. However, greater divergence between a species pair involved divergent selection on both niche dimensions. Although further replication of the trends reported here is required, the results suggest that dimensionality of selection may complement genetic and geographic explanations for the degree of diversification in nature.

The degree to which parasites use hosts is fundamental to host-parasite coevolution studies, yet difficult to assess and interpret in an evolutionary manner. Previous assessments of parasitism in eugregarine-host systems suggest high degrees of host specificity to particular host stages and host species; however, rarely have the evolutionary constraints on host specificity been studied experimentally. A series of experimental infections were conducted to determine the extent of host stadium specificity (larval vs. adult stage) and host specificity among 6 tenebrionid host species and 5 eugregarine parasite species. Eugregarines from all host species infected both the larva and adult stages of the host, and each parasite taxa colonized several host species (Tribolium spp. and Palorus subdepressus). Parasite infection patterns were not congruent with host phylogeny, suggesting that host phylogeny is not a significant predictor of host-parasite interactions in this system. However, the 2 host stages produced significantly different numbers of parasite propagules, indicating that ecological factors may be important determinants of host specificity in this host-parasite system. While field infections reflect extant natural infection patterns of parasites, experimental infections can demonstrate potential host-parasite interactions, which aids in identifying factors that may be significant in shaping future host-parasite interactions.

Following the implementation of two dams in the Senegal River, entomological and parasitological studies were conducted in three different ecological zones in the Senegal River Basin (the low valley of Senegal River, the Guiers Lake area and the low valley of Ferlo) every 3 month in June 2004, September 2004, December 2004 and March 2005. The objective of this work was to study the influence of environmental heterogeneities on vector bionomics and malaria epidemiology. Mosquitoes were collected when landing on human volunteers and by pyrethrum spray catches. In the parasitological survey, blood samples were taken from a cohort of schoolchildren under 9 years during each entomology survey. Seven anopheline species were collected: Anopheles arabiensis, Anopheles gambiae M form, Anopheles funestus, Anopheles pharoensis, Anopheles coustani, Anopheles wellcomei and Anopheles rufipes. A. arabiensis, A. funestus and A. pharoensis were predominant in the low valley of the Senegal River, A. funestus in the Guiers Lake area and A. arabiensis in the low valley of Ferlo. Mosquito populations' dynamics varied temporally depending on the rainy season for each zone. The anthropophilic rates varied between 6 and 76% for A. gambiae s.l. and 23 and 80% for A. funestus. Only 4/396 A. pharoensis and 1/3076 A. funestus tested carried Plasmodium falciparum CS antigen. These results suggest the implication of A. pharoensis in malaria transmission. The related entomological inoculation rates were estimated to 10.44 in Mbilor and 3 infected bites in Gankette Balla and were due, respectively, to A. pharoensis and A. funestus. Overall, 1636 thick blood smears were tested from blood samples taken from schoolchildren with, respectively, a parasite and gametocyte average prevalence of 9 and 0.9%. The parasite prevalence was uniformly low in Mbilor and Gankette Balla whereas; it increased in September (16%) and then remained stable in December and March (22%) in Mboula where malaria transmission was not perceptible. However, significant differences were observed over time for parasite prevalence in Mbilor and Mboula villages whereas; it was only in Gankette Balla village where gametocyte prevalence was significantly different over time. Our study demonstrates the influence of ecological changes resulted from dams implementation in the Senegal River on the composition of vectorial system, malaria transmission and epidemiology. Such changes should be thoroughly surveyed in order to prevent any possible malaria outbreak in the Senegal River Basin.

Coinfection of a host by multiple parasite species has important epidemiological and clinical implications. However, the direction and magnitude of effects vary considerably among systems, and, until now, there has been no general framework within which to explain this variation. Community ecology has great potential for application to such problems in biomedicine. Here, metaanalysis of data from 54 experiments on laboratory mice reveals that basic ecological rules govern the outcome of coinfection across a broad spectrum of parasite taxa. Specifically, resource-based ("bottom-up") and predator-based ("top-down") control mechanisms combined to determine microparasite population size in helminth-coinfected hosts. Coinfection imposed bottom-up control (resulting in decreased microparasite density) when a helminth that causes anemia was paired with a microparasite species that requires host red blood cells. At the same time, coinfection impaired top-down control of microparasites by the immune system: the greater the helminth-induced suppression of the inflammatory cytokine interferon (IFN)-gamma, the greater the increase in microparasite density. These results suggest that microparasite population growth will be most explosive when underlying helminths do not impose resource limitations but do strongly modulate IFN-gamma responses. Surprisingly simple rules and an ecological framework within which to analyze biomedical data thus emerge from analysis of this dataset. Through such an interdisciplinary lens, predicting the outcome of coinfection may become tractable.

Plants are members of complex communities and interact both with antagonists and beneficial organisms. An important question in plant defense-signaling research is how plants integrate signals induced by pathogens, beneficial microbes and insects into the most appropriate adaptive response. Molecular and genomic tools are now being used to uncover the complexity of the induced defense signaling networks that have evolved during the arms races between plants and their attackers. Molecular biologists and ecologists are joining forces to place molecular mechanisms of plant defense into an ecological perspective. Here, we review our current understanding of the molecular mechanisms of induced plant defense and their potential ecological relevance in nature.

In recent years there has been an increasing number of papers showing how parasitism and pollution can interact with each other in aquatic organisms. Apart from parasitological aspects these interactions are also important in terms of ecotoxicological research. The current presentation aims at identifying three promising directions for future research in the interdisciplinary field of parasitology and ecotoxicology. 1. Parasites as sinks for pollutants within their hosts: Some parasites are able to reduce pollutant levels in the tissues of their host. The reduction of pollutants is an interesting implication since parasites are beneficial to their hosts from this perspective. In other cases free-living accumulation indicators may erroneously indicate low levels of pollution if they are infected with parasites. 2. Parasites as a diagnostic tool to test bioavailability of substances. In order to take up and accumulate pollutants the substances have to be metabolized by the host first. Accordingly, the detection of substances within endoparasites is a sign for the biological availability of pollutants. 3. Changes of biomarker responses of the host against pollutants. Parasites can alter physiological reactions of their hosts against pollutants in different ways. Therefore, in ecotoxicological studies, examining the question whether exposure to certain chemicals affects the physiological homeostasis of a test organism, it is important to use organisms that are known to be uninfected.

The parasite fauna of young-of-the-year herring Clupea harengus L., off Gullmarsfjord and Brofjorden, west coast of Sweden, was studied between May and October for 4 years, from 1994 to 1997. Fifteen species of parasites were found: two Protozoa - Trichodina sp. and Ceratomyxa auerbachi; one species of uncertain affinity - Ichthyophonus hoferi; two Monogenea - Gyrodactylus harengi and Pseudanthocotyloides heterocotyle; five Digenea - Cryptocotyle lingua metacercariae, Cercaria pythionike metacercariae, Hemiurus luehei, Lecithaster confusus and Pseudobacciger harengulae; three Cestoda plerocercoids - Bothriocephalus sp., an acrobothriid and a tetraphyllid; one Nematoda - Hysterothylacium aduncum larva; and one Copepoda - Caligus elongatus. The number of species found in this study represents more than one-sixth of all parasites reported in herring worldwide and all parasites were acquired locally. The parasite fauna of herring from the west coast of Sweden is compared with that of herring from the Baltic Sea and other areas of the north-east Atlantic. The prevalence and intensity of parasites are presented and discussed. Morphological descriptions are based on both light and scanning electron microscopy and new features are described. Possible applications of this new information about the parasite fauna, in different areas of fisheries and fish biology studies, are discussed.

As a scientific discipline matures, its theoretical underpinnings tend to consolidate around a few general laws that explain a wide range of phenomena, and from which can be derived further testable predictions. It is one of the goals of science to uncover the general principles that produce recurring patterns in nature. Although this has happened in many areas of physics and chemistry, ecology is yet to take this important step. Ecological systems are intrinsically complex, but this does not necessarily mean that everything about them is unpredictable or chaotic. Ecologists, whose grand aim is to understand the interactions that govern the distribution, abundance and diversity of living organisms at different scales, have uncovered several regular patterns, i.e. widely observable statistical tendencies, in the abundance or diversity of organisms in natural ecosystems. Some of these patterns, however, are contingent, i.e. they are only true under particular circumstances; nevertheless, the broad generality of many patterns hints at the existence of universal principles. What about parasite ecology: is it also characterized by recurring patterns and general principles? Evidence for repeatable empirical patterns in parasite ecology is reviewed here, in search of patterns that are consistently detectable across taxa or geographical areas. The coverage ranges from the population level all the way to large-scale patterns of parasite diversity and abundance (or biomass) and patterns in the structure of host-parasite interaction networks. Although general laws seem to apply to these extreme scales of studies, most patterns observed at the intermediate scale, i.e. the parasite community level, appear highly contingent and far from universal. The general laws uncovered to date are proving valuable, as they offer glimpses of the underlying processes shaping parasite ecology and diversity.

In natural systems, individuals are often co-infected by many species of parasites. However, the significance of interactions between species and the processes that shape within-host parasite communities remain unclear. Studies of parasite community ecology are often descriptive, focusing on patterns of parasite abundance across host populations rather than on the mechanisms that underlie interactions within a host. These within-host interactions are crucial for determining the fitness and transmissibility of co-infecting parasite species. Here, we highlight how techniques from community ecology can be used to restructure the approaches used to study parasite communities. We discuss insights offered by this mechanistic approach that will be crucial for predicting the impact on wildlife and human health of disease control measures, climate change or novel parasite species introductions.

A total 89 fish and lamprey species has been recorded from Polish freshwater habitats. Twenty-seven of them (30.3%) have not been surveyed for parasitic helminthes. Some of the latter fishes are either rare or not easily accessible. Other live only in specific habitats in scattered localities. An important obstacle for studying parasite faunas of some fishes may be their status on an endangered species. Among the non-surveyed fishes, are those which have been relatively recently introduced to Poland or migrated there on their own. The present paper attempts to review all hitherto not studied helminthologically fish species, their habitats, localities and current protection status.