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Species diversity reduces parasite infection through cross-generational effects on host abundance
Ecology
Abstract and Figures
With growing interest in the effects of biodiversity on disease, there is a critical need for studies that empirically identify the mechanisms underlying the diversity-disease relationship. Here, we combined wetland surveys of host community structure with mechanistic experiments involving a multi-host parasite to evaluate competing explanations for the dilution effect. Sampling of 320 wetlands in California indicated that snail host communities were strongly nested, with competent hosts for the trematode Ribeiroia ondatrae predominating in low-richness assemblages and unsuitable hosts increasingly present in more diverse communities. Moreover, competent host density was negatively associated with increases in snail species richness. These patterns in host community assembly support a key prerequisite underlying the dilution effect. Results of multigenerational mesocosm experiments designed to mimic field-observed community assemblages allowed us to evaluate the relative importance of host density and diversity in influencing parasite infection success. Increases in snail species richness (from one to four species) had sharply negative effects on the density of infected hosts (-90% reduction). However, this effect was indirect; competition associated with non-host species led to a 95% reduction in host density (susceptible host regulation), owing primarily to a reduction in host reproduction. Among susceptible hosts, there were no differences in infection prevalence as a function of community structure, indicating a lack of support for a direct effect of diversity on infection (encounter reduction). In monospecific conditions, higher initial host densities increased infection among adult hosts; however, compensatory reproduction in the low-density treatments equalized the final number of infected hosts by the next generation, underscoring the relevance of multigenerational studies in understanding the dilution effect. These findings highlight the role of interspecific competition in mediating the relationship between species richness and parasite infection and emphasize the importance of field-informed experimental research in understanding mechanisms underlying the diversity-disease relationship.
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... For example, the presence of competitors can reduce parasitism by allowing competitors to consume infectious environmental stages of the parasite (Civitello, Pearsall, Duffy, & Hall, 2013). Conversely, the presence of competitors may increase parasite abundance if one host disproportionately amplifies parasites (Johnson, Preston, et al., 2012), or if competition reduces host condition, thereby increasing susceptibility to parasites (Murray et al., 2006;Randolph & Dobson, 2012;Strauss, Civitello, Cáceres, & Hall, 2015). Beyond these relatively simple scenarios, realistic and diverse communities will exhibit more complex and cascading indirect effects, with combinations of direct effects (competition and parasitism) and indirect effects (e.g. ...
... Regardless, these trade-offs are often ultimately mediated by differences in life-history traits (e.g. fast-slow continuum; Johnson, Rohr, et al., 2012;Johnson, Preston, et al., 2012), which can lead to coexistence when superior competitors are more susceptible to disease, mitigating competitive asymmetries among hosts. Conversely, a negative relationship can occur when poor competitive ability leads to reduced body condition, increasing susceptibility to, or costs of, parasitism (Roznik, Sapsford, Pike, Schwarzkopf, & Alford, 2015). ...
... Trait-mediated effects provide an interesting framework in which to consider the relationship between parasitism, competition and their ultimate ecological effects (Michalakis & Hochberg, 1994). Indeed, previous studies have suggested that common life-history traits may underlie the relationship between host competence and competitive ability (Johnson, Preston, et al., 2012;Johnson, Rohr, et al., 2012). More proximately, host and parasite traits can affect how hosts interact with parasites. ...
Parasitism and competition are both ubiquitous interactions in ecological communities. The ability of host species to interact directly via competition and indirectly through shared parasites suggests that host traits related to competition and parasitism are likely important in structuring communities and disease dynamics. Specifically, those host traits affecting competition and those mediating parasitism are often correlated either because of trade‐offs (in resource acquisition or resource allocation) or condition dependence, yet the consequences of these trait relationships for community and epidemiological dynamics are poorly understood.
We conducted a literature review of parasite‐related host traits–competitive ability relationships. We found that transmission–competitive ability relationships were most often reported, and that superior competitors exhibited elevated transmission relative to their less‐competitive counterparts in nearly 80% of the cases. We also found a significant number of virulence–competitive ability and parasite shedding–competitive ability relationships.
We investigated these links by altering the relationship between host competitive ability and three parasite‐related traits (transmission, virulence and parasite shedding rates) in a simple model, incorporating competitive asymmetries in a multi‐host community.
We show that these relationships can lead to a range of different communities. For example, depending on the strength and direction of these distinct trait relationships, we observed communities with anywhere from high parasite prevalence to complete parasite extinction, and either one, two or the maximum of three host species coexisting.
Our results suggest that parasite–competitive ability relationships may be common in nature, that further integration of these relationships can produce novel and unexpected community and disease dynamics, and that generalizations may allow for the prediction of how parasitism and competition jointly structure disease and diversity in natural communities.
... Based on theory, stage-specific biomass overcompensation should occur when intraspecific competition is strong, life stages differ in competitive ability, and changes in demographic rates (e.g., growth, survival, or reproduction) relax density dependence in the life stage that limits biomass production . Exploitative competition commonly structures freshwater snail populations (Chase et al. 2001, Johnson et al. 2012, and juvenile snails typically have higher mass-specific ingestion rates than adults (e.g., Tamburi and Mart ın 2009). Furthermore, trematode infection probability increases with snail age/size and infection castrates adult snail hosts, sometimes with concurrent decreases in snail survival (Sorensen andMinchella 2001, Poulin 2011). ...
... The focal trematodes fully castrate their adult snail hosts and moderately reduce host survival, but are not known to alter host ingestion rates, individual growth, or cause gigantism (J. T. Hoverman et al. unpublished data;Sorensen and Minchella 2001, Johnson et al. 2012, Preston et al. 2013. The two snail taxa commonly co-occur in natural wetlands and the outcome of their competitive interactions depends on environmental conditions, with neither species being clearly competitively dominant (Chase et al. 2001). ...
Predators can increase the biomass of their prey, particularly when prey life stages differ in competitive ability and predation is stage specific. Akin to predators, parasites influence host population sizes and engage in stage‐structured interactions, yet whether parasites can increase host population biomass remains relatively unexplored. Using a stage‐structured consumer–resource model and a mesocosm experiment with snails and castrating trematodes, we examined responses of host biomass to changes in infection prevalence under variation in host pathology and resource competition. Equilibrium adult host biomass increased with infection prevalence in the model when parasites castrated hosts and adults were superior competitors to juveniles. Juvenile biomass increased with infection prevalence whether parasites caused mortality or castration, but only when juveniles were superior competitors. In mesocosms, increases in infection by castrating trematodes reduced snail egg production, juvenile abundance, and adult survival. At high competition, juvenile growth and total biomass increased with infection prevalence due to competitive release. At low competition, juvenile biomass decreased with infection due to reduced reproduction. These results highlight how disease‐induced biomass overcompensation depends on infection pathology, resource availability, and competitive interactions within and between host life stages. Considering such characteristics may benefit biocontrol efforts using parasites.
... Experimental and modeling studies focusing on the dilution effect have traditionally assumed nested communities, which are often observed in nature (Johnson et al., 2012;Wright et al., 1997), and additivity (e.g., Johnson et al., 2013;Roche et al., 2013), although a realistic community might be assembled following a tradeoff between additive and substitutive extremes (Becker et al., 2014;Mihaljevic et al., 2014). It is not likely that total host density increases linearly (i.e., additively) with increasing species richness because the species added to the community might be competitors or predators of reservoir hosts (Levi, Keesing, et al., 2016). ...
Disease (re)emergence appears to be driven by biodiversity decline and environmental change. As a result, it is increasingly important to study host–pathogen interactions within the context of their ecology and evolution. The dilution effect is the concept that higher biodiversity decreases pathogen transmission. It has been observed especially in zoonotic vector‐borne pathosystems, yet evidence against it has been found. In particular, it is still debated how the community (dis)assembly assumptions and the degree of generalism of vectors and pathogens affect the direction of the biodiversity–pathogen transmission relationship. The aim of this study was to use empirical data and mechanistic models to investigate dilution mechanisms in two rodent–tick–pathogen systems differing in their vector degree of generalism. A community was assembled to include ecological interactions that expand from purely additive to purely substitutive. Such systems are excellent candidates to analyze the link between vector ecology, community (dis)assembly dynamics, and pathogen transmission. To base our mechanistic models on empirical data, rodent live‐trapping, including tick sampling, was conducted in Wales across two seasons for three consecutive years. We have developed a deterministic single‐vector, multi‐host compartmental model that includes ecological relationships with non‐host species, uniquely integrating theoretical and observational approaches. To describe pathogen transmission across a gradient of community diversity, the model was populated with parameters describing five different scenarios differing in ecological complexity; each based around one of the pathosystems: Ixodes ricinus (generalist tick)–Borrelia burgdorferi and I. trianguliceps (small mammals specialist tick)–Babesia microti. The results suggested that community composition and interspecific dynamics affected pathogen transmission with different dilution outcomes depending on the vector degree of generalism. The model provides evidence that dilution and amplification effects are not mutually exclusive in the same community but depend on vector ecology and the epidemiological output considered (i.e., the “risk” of interest). In our scenarios, more functionally diverse communities resulted in fewer infectious rodents, supporting the dilution effect. In the pathosystem with generalist vector we identified a hump shaped relationship between diversity and infections in hosts, while for that characterized by specialist tick, this relationship was more complex and more dependent upon specific parameter values.
... In communities with substitutive, non-random assembly, species-level disease risk was lower in richer communities because there were fewer competent hosts, such as radish and arugula. 'Competent host regulation' (modified sensu Keesing et al. 2006) suggests that fewer competent hosts lead to lower transmission risk, and is often evoked to explain dilution effects (Strauss et al. 2015, Johnson et al. 2012. Species-level disease prevalence across all trays was positively associated with richness when density of all species was incorporated into the model; however, the marginal effect of richness was negligible after also conditioning upon the densities of individual species (Appendix S2: Table S1). ...
Since species vary in abundance and host competence (i.e., ability to get infected and transmit a pathogen), changes in species composition caused by biodiversity loss impacts disease dynamics. Forecasting effects of species composition on disease depends on community (dis)assembly, processes determining how species are added to (or lost from) communities. We simulated community assembly by planting mesocosms, nested along a richness gradient, and tested how relationships between richness, species assembly order, and overall density affect disease risk. Mesocosms with up to six crop species of varying competence were inoculated with a soilborne fungal pathogen, Rhizoctonia solani. Disease was measured as species‐level prevalence, community‐level prevalence, and total number of diseased plants. Regardless of metric, richness limited disease when species assembly order negatively correlated with competence and total density remained unchanged with richness. When density increased with richness or species assembled randomly, richness primarily correlated positively or weakly with disease. Our results align with theoretical expectations and represent the first empirical study to test the influence of species densities, assembly order, and competence on diversity–disease relationships.
... 'Diluter' species might regulate the densities of high-competence hosts, or those that efficiently acquire and transmit pathogens, via competition for finite resources (Figure 1a; Strauss et al., 2015). Decreases in diversity have been associated with increases in infections for plant, animal, and zoonotic diseases (Johnson et al., 2012;Mitchell et al., 2002;Ostfeld & Keesing, 2000). Covariance between competent host densities and diversity likely depends on additional relationships among host competence, nestedness and total density. ...
Understanding why diversity sometimes limits disease is essential for managing outbreaks; however, mechanisms underlying this ‘dilution effect’ remain poorly understood. Negative diversity-disease relationships have previously been detected in plant communities impacted by an emerging forest disease, sudden oak death. We used this focal system to empirically evaluate whether these relationships were driven by dilution mechanisms that reduce transmission risk for individuals or from the fact that disease was averaged across the host community. We integrated laboratory competence measurements with plant community and symptom data from a large forest monitoring network. Richness increased disease risk for bay laurel trees, dismissing possible dilution mechanisms. Nonetheless, richness was negatively associated with community-level disease prevalence because the disease was aggregated among hosts that vary in disease susceptibility. Aggregating observations (which is surprisingly common in other dilution effect studies) can lead to misinterpretations of dilution mechanisms and bias towards a negative diversity-disease relationship.
... External parasites are also subjected to a strong selection, which can lead to convergent evolved phenotypes among one or more species. Furthermore, a strong selective pressure on loci, which controls morphological differences in organisms, can be caused by genetic isolation of the population of each host and the adaptation to a particular host [19,21]. ...
Purpose
The main aim of our study was to examine morphological differentiation between and within sex of hen fleas-Ceratophyllus gallinae (Schrank, 1803) population collected from Eurasian blue tit (Cyanistes caeruleus Linnaeus, 1758), inhabiting nest boxes and to determine the morphological parameters differentiating this population.
Methods
A total of 296 fleas were collected (148 females and 148 males), determined to species and sex, then the following characters were measured in each of the examined fleas: body length, body width, length of head, width of head, length of comb, height of comb, length of tarsus, length of thorax and length of abdomen.
Results
The comparison of body size showed the presence of two groups among female and male life forms of the hen flea, which mostly differed in length of abdomen, whereas the length of head and tarsus III were less variable.
Conclusion
Till now, the only certain information is the presence of two adult life forms of C. gallinae. The genesis of their creation is still unknown and we are not able to identify the mechanism responsible for the morphological differentiation of fleas collected from the same host. In order to find answer to this question, future research in the field of molecular taxonomy is required.
... That is, the presence of other significant hosts like ducks, chickens, wild bird-dwellers, and amphibians which may harbor different parasites is evident from the area and may provide a rational explanation for the existence of these other types of cercariae. This supports the dilution effect hypothesis that underscores the relevance of negative correlation between disease incidence and host diversity [43]. Arguably, this hypothesis may not be always consistent in most human infections with great public health impact [44]. ...
Background and Objectives. Lymnaeid snails are the known intermediate hosts of the liver fluke Fasciola spp. and therefore play an important role in the parasite’s life cycle. The study is conducted to determine specificity of snail host-parasite interaction and to determine the snail-trematode infection rate by cercarial emergence, characterizing the emerging larvae using standardized key. Materials and Methods. A total of 750 snails were collected from a rice field in Barangay Cawongan, Padre Garcia, Batangas, from November 2016 to March 2017 (n=150/month). Preliminary snail identification was based on morphological features of the shell. Each snail was acclimatized for 24 hours in a 50-ml capacity container before being exposed to strong artificial light. The 150 snails collected per month were grouped into 5 batches (n=30/batch) with each batch receiving different number of light exposures. Emerging cercariae were described and characterized using photo-referencing and standardized keys. All statistical tests were performed at p
Soils influence human health in many ways, both positive and negative. These include the supply of nutrients; exposure to heavy metals, organic chemicals, and pathogens; the supply of antibiotics and other medicines; and soils may even support mental health. Soils can impact all aspects of the human system, from the skin to the respiratory tract, digestive and nervous systems, and beyond. Human management of the soil system can have a major impact on these influences. In particular, any management that supports soil health also supports human health. Establishing the health of a soil involves the measurement of soil biological, chemical, and physical properties. Future needs in the area of soil and human health include well-designed scientific studies that investigate the links between soil abiotic and biotic properties and human health as well as soil science links to soils and human health.
Among population dynamics drivers, parasitism is significant but often neglected. Beyond inventory of the various parasites, it is urgent to understand the susceptibility of hosts, namely bivalves, to infection, and to investigate the interaction among parasites and other environmental conditions.In this way, the present study aimed to characterize and quantify the trematode macroparasites, the most abundant and prevalent in coastal waters, infecting Cerastoderma edule and Donax trunculus, which are among the most ecologically important and economically explored bivalve species in Portugal and France.The first step was to study bivalve population dynamics, evaluating the relationship between temperature and recruitment timing and the reciprocal effects of recruitment on adult biomass. For this, a large database spanning 17 years of monthly observations of a cockle population inhabiting a national protected area (Banc d’Arguin, Arcachon, France) was analysed. Long-term observations showed that the sustainability of a cockle population is recruitment-success dependent. In cockles, recruitment success showed to be partly, but not only, dependent on temperature. Hence, the sustainability of a cohort could be set earlier, i.e. by processes happening before recruitment. Following this clue, the role of parasitism on the bivalve host population dynamics was explored.Firstly, due to high pathogenicity for bivalves, special attention was given to the parasites Bucephalus minimus and Bacciger bacciger which use C. edule and D. trunculus, respectively, as first intermediate hosts (where their sporocysts parasitic stage develops). […]Then, the study focused on metacercariae infection in its bivalve second intermediate host, a relationship that is usually reported as less deleterious. […]Lastly, the susceptibility of bivalves to parasites infection when challenged by climate change related factors (salinity, temperature and pH) and contamination (Arsenic) was experimentally assessed. Main results showed that hosts exposure to stressful conditions related to global change scenarios can modify the parasite infection success and induced host biochemical response alterations.The findings presented in this thesis improved the knowledge on the effects of different constraints on bivalves, highlighting the crucial role of parasitism. If applied, these new insights can promote the sustainable management of bivalves, such an important marine resource, with greater production and economic potential.
Linear regression and analysis of variance (ANOVA) are two of the most widely used statistical techniques in ecology. Regression quantitatively describes the relationship between a response variable and one or more continuous independent variables, while ANOVA determines whether a response variable differs among discrete values of the independent variable(s). Designing experiments with discrete factors is straightforward because ANOVA is the only option, but what is the best way to design experiments involving continuous factors? Should ecologists prefer experiments with few treatments and many replicates analyzed with ANOVA, or experiments with many treatments and few replicates per treatment analyzed with regression? We recommend that ecologists choose regression, especially replicated regression, over ANOVA when dealing with continuous factors for two reasons: (1) regression is generally a more powerful approach than ANOVA and (2) regression provides quantitative output that can be incorporated into ecological models more effectively than ANOVA output.
Utilitarian arguments concerning the value of biodiversity often include the benefits of animals, plants, and microbes as sources of medicines and as laboratory models of disease. The concept that species diversity per se may influence risk of exposure to disease has not been well developed, however. We present a conceptual model of how high species richness and evenness in communities of terrestrial vertebrates may reduce risk of exposure to Lyme disease, a spirochetal ( Borrelia burgdorferi) disease transmitted by ixodid tick vectors. Many ticks never become infected because some hosts are highly inefficient at transmitting spirochete infections to feeding ticks. In North America, the most competent reservoir host for the Lyme disease agent is the white-footed mouse ( Peromyscus leucopus), a species that is widespread and locally abundant. We suggest that increases in species diversity within host communities may dilute the power of white-footed mice to infect ticks by causing more ticks to feed on inefficient disease reservoirs. High species diversity therefore is expected to result in lower prevalence of infection in ticks and consequently in lower risk of human exposure to Lyme disease. Analyses of states and multistate regions along the east coast of the United States demonstrated significant negative correlations between species richness of terrestrial small mammals (orders Rodentia, Insectivora, and Lagomorpha), a key group of hosts for ticks, and per capita numbers of reported Lyme disease cases, which supports our “dilution effect” hypothesis. We contrasted these findings to what might be expected when vectors acquire disease agents efficiently from many hosts, in which case infection prevalence of ticks may increase with increasing diversity hosts. A positive correlation between per capita Lyme disease cases and species richness of ground-dwelling birds supported this hypothesis, which we call the “rescue effect.” The reservoir competence of hosts within vertebrate communities and the degree of specialization by ticks on particular hosts will strongly influence the relationship between species diversity and the risk of exposure to the many vector-borne diseases that plague humans.
Resumen: Argumentos utilitarios relacionados con el valor de la biodiversidad frecuentemente incluyen los beneficios de animales, plantas y microbios como recursos para medicinas y como modelos de enfermedades en laboratorio. Sin embargo, la idea de que la diversidad de especies por sí misma puede influenciar el riesgo de exposición a enfermedades no ha sido bien desarrollada. Presentamos un modelo conceptual de cómo la riqueza de especies y la uniformidad en comunidades de vertebrados terrestres puede reducir el riesgo de exposición a la enfermedad de Lyme, una enfermedad causada por una espiroqueta ( Borrelia burgdorferi) y transmitida por una garrapata ixódida. Muchas garrapatas nunca son infectadas debido a que los huéspedes son altamente ineficientes en la transmisión de espiroquetas a las garrapatas que se alimentan de ellos. En Norte América, el huésped reservorio más competente del agente de la enfermedad de Lyme es el ratón de patas blancas ( Peromyscus leucopus), una especie de amplia dispersión y localmente abundante. Sugerimos que los incrementos en la diversidad de especies dentro de las comunidades de huéspedes pueden diluir el potencial de infección de las garrapatas por el ratón de patas blancas al ocasionar que más garrapatas se alimenten de reservorios ineficientes en la transmisión de la enfermedad. Por lo tanto, se esperaría que una alta diversidad de especies resulte en una prevalencia de infección de garrapatas reducida y, por lo tanto, en una disminución del riesgo de exposición de humanos a la enfermedad de Lyme. Un análisis por estado y de varios estados a lo largo de la costa este de los Estados Unidos demostró correlaciones significativamente negativas entre la riqueza de especies de mamíferos terrestres pequeños (órdenes Rodentia, Insectivora, y Lagomorfa), un grupo clave de huéspedes para garrapatas, y los números per capita de casos de la enfermedad de Lyme reportados, lo cual apoya nuestra hipótesis de efecto de dilución. Contrastamos estos resultados con lo que se podría esperar cuando los vectores adquieren eficientemente agentes de la enfermedad de muchos huéspedes, caso en el cual, una alta diversidad causaría la prevalencia de infección de garrapatas permaneciendo alta aún cuando la diversidad de huéspedes disminuyera. Una correlación positiva entre los casos de la enfermedad de Lyme per capita y la riqueza de especies de aves residentes del suelo apoya esta hipótesis, que hemos llamado efecto de rescate. La capacidad de reservorio de huéspedes dentro de las comunidades de vertebrados y el grado de especialización de las garrapatas en huéspedes particulares, influenciaría fuertemente la relación entre la diversidad de especies y el riesgo de exposición a muchas de las enfermedades transmitidas por vectores que infectan a humanos.
This chapter review insights that have been gained from studies that explicitly acknowledge the contribution of multiple hosts to the dynamics of pathogens. I start from a simple, deterministic viewpoint, distinguishing the contrasting possible effects that a multiplicity of hosts can have on pathogen dynamics, either favoring pathogen per sis tence or high pathogen abundance (amplifi cation) or reducing these (including especially the dilution effect). A review of the limited available data suggests that although the theoretical possibility of pathogen amplifi cation by multiple hosts is clear, it is not inevitable, in part because transmission between species is rarer than has sometimes been imagined. It is emphasized that it may often be diffi cult to separate a dilution effect from a simple density effect: their outcomes (reduced pathogen abundance when host diversity is greater) may be the same, but the underlying biological mechanism, which is taken here to defi ne the dilution effect, is quite different. Some empirical evidence for a dilution effect exists, but even for the most studied system, Lyme disease, there seems little empirical basis for distinguishing between a dilution effect and an effect of mouse density, and therefore little evidence either, in spite of its plausibility, for a dilution effect. I then ask briefl y what further possibilities may arise with a shift to a (more realistic) perspective in which key pro cesses are stochastic, dynamics are not necessarily equilibrial, and hosts exist as metapopulations. Finally, I consider even more briefl y the possible evolutionary consequences of pathogen dynamics driven by a multiplicity of hosts.
The causes of amphibian deformities and their role in widespread amphibian declines remain conjectural. Severe limb abnormalities
were induced at high frequencies in Pacific treefrogs (Hyla regilla) exposed to cercariae of a trematode parasite (Ribeiroia sp.). The abnormalities closely matched those observed at field sites, and an increase in parasite density caused an increase
in abnormality frequency and a decline in tadpole survivorship. These findings call for further investigation of parasite
infection as a cause of amphibian deformities in other sites and species.
Aplexa hypnorum studied in NE Indiana is a specialist in both habitat and food use, and is detritivore in heavily wooded, temporary ponds. Lymnaea elodes is more common in partially wooded, temporary ponds, and specializes on periphyton and carrion. Physa gyrina has a broad utilization of both the habitat and food dimensions of the niche. Helisoma trivolvis is a generalist in food preference, but was common only in a permanent pond. These data, and niche overlap estimates, predict that L. elodes and P. gyrina should have the greatest overlap on resources. Field experiments suggest that high overlap along the habitat and dietary dimensions of the niche results in competition in these freshwater snails. Interspecific competition decreased fecundity in P. gyrina, but not in L. elodes. For both species, interspecific competition had less of an effect than increased conspecific densities on growth rates. Physa generally did better in the less productive, temporary ponds, while L. elodes had higher fecundities and growth rates in a permanent, more productive pond. Lymnaea elodes was considered the better competitor because interspecific competition had smaller effects on growth and reproduction than intraspecific competition. The earlier reproducing P. gyrina may be able to exploit more ephemeral habitats as refuges. -from Author
News headlines are forever reporting diseases that take huge tolls on humans, wildlife, domestic animals, and both cultivated and native plants worldwide. These diseases can also completely transform the ecosystems that feed us and provide us with other critical benefits, from flood control to water purification. And yet diseases sometimes serve to maintain the structure and function of the ecosystems on which humans depend.Gathering thirteen essays by forty leading experts who convened at the Cary Conference at the Institute of Ecosystem Studies in 2005, this book develops an integrated framework for understanding where these diseases come from, what ecological factors influence their impacts, and how they in turn influence ecosystem dynamics. It marks the first comprehensive and in-depth exploration of the rich and complex linkages between ecology and disease, and provides conceptual underpinnings to understand and ameliorate epidemics. It also sheds light on the roles that diseases play in ecosystems, bringing vital new insights to landscape management issues in particular. While the ecological context is a key piece of the puzzle, effective control and understanding of diseases requires the interaction of professionals in medicine, epidemiology, veterinary medicine, forestry, agriculture, and ecology. The essential resource on the subject,Infectious Disease Ecologyseeks to bridge these fields with an ecological approach that focuses on systems thinking and complex interactions.