The role of tropical rainfall in driving range dynamics for a long-distance migratory bird.

Predicting how the range dynamics of migratory species will respond to climate change requires a mechanistic understanding of the factors that operate across the annual cycle to control the distribution and abundance of a species. Here, we use multiple lines of evidence to reveal that environmental conditions during the nonbreeding season influence range dynamics across the life cycle of a migratory songbird, the American redstart (Setophaga ruticilla). Using long-term data from the nonbreeding grounds and breeding origins estimated from stable hydrogen isotopes in tail feathers, we found that the relationship between annual survival and migration distance is mediated by precipitation, but only during dry years. A long-term drying trend throughout the Caribbean is associated with higher mortality for individuals from the northern portion of the species' breeding range, resulting in an approximate 500 km southward shift in breeding origins of this Jamaican population over the past 30 y. This shift in connectivity is mirrored by changes in the redstart's breeding distribution and abundance. These results demonstrate that the climatic effects on demographic processes originating during the tropical nonbreeding season are actively shaping range dynamics in a migratory bird.

Coproduction and modeling spatial contact networks prevent bias about infectious hematopoietic necrosis virus transmission for Snake River Basin salmonids.

Much remains unknown about variation in pathogen transmission across the geographic range of a free-ranging fish or animal species and about the influence of movement (associated with husbandry practices or animal behavior) on pathogen transmission. Salmonid hatcheries are an ideal system in which to study these processes. Salmonid hatcheries are managed for endangered species recovery, supplementation of threatened or at-risk fish stocks, support of fisheries, and ecosystem stability. Infectious hematopoietic necrosis virus (IHNV) is a rhabdovirus of significant concern to salmon aquaculture. Landscape IHNV transmission dynamics previously had been estimated only for salmonid hatcheries in the Lower Columbia River Basin (LCRB). The objectives of this study were to estimate IHNV transmission dynamics in a unique geographic region, the Snake River Basin (SRB), and to quantitatively estimate the effect of model coproduction on inference because previous assessments of coproduction have been qualitative. In contrast to the LCRB, the SRB has hatchery complexes consisting of a main hatchery and ≥1 satellite facility. Knowledge about hatchery complexes was held by a subset of project researchers but would not have been available to project modelers without coproduction. Project modelers generated and tested multiple versions of Bayesian susceptible-exposedinfected models to realistically represent the SRB and estimate the effect of coproduction. Models estimated the frequency of transmission routes, route-specific infection probabilities, and infection probabilities for combinations of salmonid hosts and IHNV lineages. Model results indicated that in the SRB, avoiding exposure to IHNV-positive adult salmonids is the most important action to prevent juvenile infections. Migrating adult salmonids exposed juvenile cohort-sites most frequently, and the infection probability was greatest following exposure to migrating adults. Without coproduction, the frequency of exposure by migrating adults would have been overestimated by 70 cohort-sites, and the infection probability following exposure to migrating adults would have been underestimated by∼0.09. The coproduced model had less uncertainty in the infection probability if no transmission route could be identified (Bayesian credible interval (BCI) width = 0.12) compared to the model without coproduction (BCI width = 0.34). Evidence for virus lineage MD specialization on steelhead and rainbow trout (both Oncorhynchus mykiss) was apparent without model coproduction. In the SRB, we found a greater probability of virus lineage UC infection in Chinook salmon (Oncorhynchus tshawytscha) compared to in O. mykiss, whereas in the LCRB, UC more clearly exhibited a generalist approach. Coproduction influenced estimates that depended on transmission routes, which operated differently at main hatcheries and satellite sites within hatchery complexes. Hatchery complexes are found outside of the SRB and are not specific to salmonid hatcheries alone. There is great potential for coproduction and modeling spatial contact networks to advance understanding about infectious disease transmission in complex production systems and surrounding free-ranging animal populations.

Using near-term forecasts and uncertainty partitioning to inform prediction of oligotrophic lake cyanobacterial density.

Near-term ecological forecasts provide resource managers advance notice of changes in ecosystem services, such as fisheries stocks, timber yields, or water quality. Importantly, ecological forecasts can identify where there is uncertainty in the forecasting system, which is necessary to improve forecast skill and guide interpretation of forecast results. Uncertainty partitioning identifies the relative contributions to total forecast variance introduced by different sources, including specification of the model structure, errors in driver data, and estimation of current states (initial conditions). Uncertainty partitioning could be particularly useful in improving forecasts of highly variable cyanobacterial densities, which are difficult to predict and present a persistent challenge for lake managers. As cyanobacteria can produce toxic and unsightly surface scums, advance warning when cyanobacterial densities are increasing could help managers mitigate water quality issues. Here, we fit 13 Bayesian state-space models to evaluate different hypotheses about cyanobacterial densities in a low nutrient lake that experiences sporadic surface scums of the toxin-producing cyanobacterium, Gloeotrichia echinulata. We used data from several summers of weekly cyanobacteria samples to identify dominant sources of uncertainty for near-term (1- to 4-week) forecasts of G. echinulata densities. Water temperature was an important predictor of cyanobacterial densities during model fitting and at the 4-week forecast horizon. However, no physical covariates improved model performance over a simple model including the previous week's densities in 1-week-ahead forecasts. Even the best fit models exhibited large variance in forecasted cyanobacterial densities and did not capture rare peak occurrences, indicating that significant explanatory variables when fitting models to historical data are not always effective for forecasting. Uncertainty partitioning revealed that model process specification and initial conditions dominated forecast uncertainty. These findings indicate that long-term studies of different cyanobacterial life stages and movement in the water column as well as measurements of drivers relevant to different life stages could improve model process representation of cyanobacteria abundance. In addition, improved observation protocols could better define initial conditions and reduce spatial misalignment of environmental data and cyanobacteria observations. Our results emphasize the importance of ecological forecasting principles and uncertainty partitioning to refine and understand predictive capacity across ecosystems.

Rodents harbouring zoonotic pathogens take advantage of abandoned land in post-Katrina New Orleans.

Leptospirosis is a disease that disproportionately affects impoverished urban communities, but is likely to become more prevalent as changing climate alters flooding regimes. The persistence and transmission of the Leptospira pathogen is reliant on small vertebrate animals, predominantly rodents. In this issue of Molecular Ecology, Peterson et al. demonstrate how changes in rodent diversity and abundances across the complex mosaic of abandonment and recovery investment in post-Katrina New Orleans can predict zoonotic infection prevalence. Understanding the ecological conditions that support persistence and transmission of zoonotic pathogens in urban ecosystems, where they are most likely to affect humans, is critical to effective monitoring and prevention.

Theoretical Perspectives of the Baltimore Ecosystem Study: Conceptual Evolution in a Social-Ecological Research Project.

The Earth's population will become more than 80% urban during this century. This threshold is often regarded as sufficient justification for pursuing urban ecology. However, pursuit has primarily focused on building empirical richness, and urban ecology theory is rarely discussed. The Baltimore Ecosystem Study (BES) has been grounded in theory since its inception and its two decades of data collection have stimulated progress toward comprehensive urban theory. Emerging urban ecology theory integrates biology, physical sciences, social sciences, and urban design, probes interdisciplinary frontiers while being founded on textbook disciplinary theories, and accommodates surprising empirical results. Theoretical growth in urban ecology has relied on refined frameworks, increased disciplinary scope, and longevity of interdisciplinary interactions. We describe the theories used by BES initially, and trace ongoing theoretical development that increasingly reflects the hybrid biological-physical-social nature of the Baltimore ecosystem. The specific mix of theories used in Baltimore likely will require modification when applied to other urban areas, but the developmental process, and the key results, will continue to benefit other urban social-ecological research projects.

Nonnative forest insects and pathogens in the United States: Impacts and policy options.

We review and synthesize information on invasions of nonnative forest insects and diseases in the United States, including their ecological and economic impacts, pathways of arrival, distribution within the United States, and policy options for reducing future invasions. Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yr. Currently the two major pathways of introduction are importation of live plants and wood packing material such as pallets and crates. Introduced insects and diseases occur in forests and cities throughout the United States, and the problem is particularly severe in the Northeast and Upper Midwest. Nonnative forest pests are the only disturbance agent that has effectively eliminated entire tree species or genera from United States forests within decades. The resulting shift in forest structure and species composition alters ecosystem functions such as productivity, nutrient cycling, and wildlife habitat. In urban and suburban areas, loss of trees from streets, yards, and parks affects aesthetics, property values, shading, stormwater runoff, and human health. The economic damage from nonnative pests is not yet fully known, but is likely in the billions of dollars per year, with the majority of this economic burden borne by municipalities and residential property owners. Current policies for preventing introductions are having positive effects but are insufficient to reduce the influx of pests in the face of burgeoning global trade. Options are available to strengthen the defenses against pest arrival and establishment, including measures taken in the exporting country prior to shipment, measures to ensure clean shipments of plants and wood products, inspections at ports of entry, and post-entry measures such as quarantines, surveillance, and eradication programs. Improved data collection procedures for inspections, greater data accessibility, and better reporting would support better evaluation of policy effectiveness. Lack of additional action places the nation, local municipalities, and property owners at high risk of further damaging and costly invasions. Adopting stronger policies to reduce establishments of new forest insects and diseases would shift the major costs of control to the source and alleviate the economic burden now borne by homeowners and municipalities.

When is a parasite not a parasite? Effects of larval tick burdens on white-footed mouse survival.

Many animal species can carry considerable burdens of ectoparasites: parasites living on the outside of a host's body. Ectoparasite infestation can decrease host survival, but the magnitude and even direction of survival effects can vary depending on the type of ectoparasite and the nature and duration of the association. When ectoparasites also serve as vectors of pathogens, the effects of ectoparasite infestation on host survival have the potential to alter disease dynamics by regulating host populations and stabilizing transmission. We quantified the impact of larval Ixodes scapularis tick burdens on both within-season and overwinter survival of white-footed mice (Peromyscus leucopus) using a hierarchical Bayesian capture-mark-recapture model. I. scapularis and P. leucopus are, respectively, vectors and competent reservoirs for the causative agents of Lyme disease, anaplasmosis, and babesiosis. Using a data set of 5587 individual mouse capture histories over sixteen years, we found little evidence for any effect of tick burdens on either within-season or overwinter mouse survival probabilities. In male mice, tick burdens were positively correlated with within-season survival probabilities. Mean maximum tick burdens were also positively correlated with population rates of change during the concurrent breeding season. The apparent indifference of mice to high tick burdens may contribute to their effectiveness as reservoir hosts for several human zoonotic pathogens.

Socioeconomic status affects mosquito (Diptera: Culicidae) larval habitat type availability and infestation level.

Mosquito populations are largely regulated by processes occurring at the larval stage. We sampled mosquito larval microhabitats (mostly water-holding containers) in six neighborhoods in the Washington, DC, area that varied in socioeconomic status (SES) and housing structure (row houses vs. stand-alone houses) to test associations among these neighborhood characteristics, microhabitat abundance and parameters, and mosquito occurrence and densities. Thirty-four percent (33.9%) of sampled microhabitats contained mosquito larvae, and 93.1% of larvae were Aedes albopictus Skuse or Culex pipiens L. Five specific container types (drains, corrugated flexible drainpipes, planters, garbage cans, and buckets) accounted for the majority of water-holding (56.0%) and mosquito-positive (50.6%) microhabitats sampled. We found no associations between SES or housing structure with total microhabitat abundance per yard, mosquito occurrence or mosquito densities per microhabitat. In contrast, container purpose varied with SES, with low SES neighborhoods having greater numbers of disused containers and lower numbers of functional containers than low and medium SES neighborhoods. Ae. albopictus were 83% more abundant in disused containers, whereas Cx. pipiens were more abundant in structural and functional containers, possibly owing to species-specific oviposition and development related to water quality. Ae. albopictus densities increased over the summer, whereas Cx. pipiens densities remained constant. Ae. albopictus is usually the dominant pest in urban areas in the eastern United States; therefore, integrated mosquito management programs should incorporate the elimination of disused containers to reduce its infestation and adult production, especially in low SES neighborhoods where they occur most frequently.

West Nile virus emergence and large-scale declines of North American bird populations.

Emerging infectious diseases present a formidable challenge to the conservation of native species in the twenty-first century. Diseases caused by introduced pathogens have had large impacts on species abundances, including the American chestnut, Hawaiian bird species and many amphibians. Changes in host population sizes can lead to marked shifts in community composition and ecosystem functioning. However, identifying the impacts of an introduced disease and distinguishing it from other forces that influence population dynamics (for example, climate) is challenging and requires abundance data that extend before and after the introduction. Here we use 26 yr of Breeding Bird Survey (BBS) data to determine the impact of West Nile virus (WNV) on 20 potential avian hosts across North America. We demonstrate significant changes in population trajectories for seven species from four families that concur with a priori predictions and the spatio-temporal intensity of pathogen transmission. The American crow population declined by up to 45% since WNV arrival, and only two of the seven species with documented impact recovered to pre-WNV levels by 2005. Our findings demonstrate the potential impacts of an invasive species on a diverse faunal assemblage across broad geographical scales, and underscore the complexity of subsequent community response.

Changes in Container-Breeding Mosquito Diversity and Abundance Along an Urbanization Gradient are Associated With Dominance of Arboviral Vectors.

Environmental conditions associated with urbanization are likely to influence the composition and abundance of mosquito (Diptera, Culicidae) assemblages through effects on juvenile stages, with important consequences for human disease risk. We present six years (2011-2016) of weekly juvenile mosquito data from distributed standardized ovitraps and evaluate how variation in impervious cover and temperature affect the composition and abundance of container-breeding mosquito species in Maryland, USA. Species richness and evenness were lowest at sites with high impervious cover (>60% in 100-m buffer). However, peak diversity was recorded at sites with intermediate impervious cover (28-35%). Four species were observed at all sites, including two recent invasives (Aedes albopictus Skuse, Ae. japonicus Theobald), an established resident (Culex pipiens L), and one native (Cx. restuans Theobald). All four are viral vectors in zoonotic or human transmission cycles. Temperature was a positive predictor of weekly larval abundance during the growing season for each species, as well as a positive predictor of rapid pupal development. Despite being observed at all sites, each species responded differently to impervious cover. Abundance of Ae. albopictus larvae was positively associated with impervious cover, emphasizing that this medically-important vector not only persists in the warmer, impervious urban landscape but is positively associated with it. Positive temperature effects in our models of larval abundance and pupae occurrence in container habitats suggest that these four vector species are likely to continue to be present and abundant in temperate cities under future temperature scenarios.

Range-wide effects of breeding- and nonbreeding-season climate on the abundance of a Neotropical migrant songbird.

Geographic variation in the population dynamics of a species can result from regional variability in climate and how it affects reproduction and survival. Identifying such effects for migratory birds requires the integration of population models with knowledge of migratory connectivity between breeding and nonbreeding areas. We used Bayesian hierarchical models with 26 years of Breeding Bird Survey data (1982-2007) to investigate the impacts of breeding- and nonbreeding-season climate on abundance of American Redstarts (Setophaga ruticilla) across the species range. We focused on 15 populations defined by Bird Conservation Regions, and we included variation across routes and observers as well as temporal trends and climate effects. American Redstart populations that breed in eastern North America showed increased abundance following winters with higher plant productivity in the Caribbean where they are expected to overwinter. In contrast, western breeding populations showed little response to conditions in their expected wintering areas in west Mexico, perhaps reflecting lower migratory connectivity or differential effects of winter rainfall on individuals across the species range. Unlike the case with winter climate, we found few effects of temperature prior to arrival in spring (March-April) or during the nesting period (May-June) on abundance the following year. Eight populations showed significant changes in abundance, with the steepest declines in the Atlantic Northern Forest (-3.4%/yr) and the greatest increases in the Prairie Hardwood Transition (4%/yr). This study emphasizes how the effects of climate on populations of migratory birds are context dependent and can vary depending on geographic location and the period of the annual cycle. Such knowledge is essential for predicting regional variation in how populations of a species might vary in their response to climate change.

Data-model fusion to better understand emerging pathogens and improve infectious disease forecasting.

Ecologists worldwide are challenged to contribute solutions to urgent and pressing environmental problems by forecasting how populations, communities, and ecosystems will respond to global change. Rising to this challenge requires organizing ecological information derived from diverse sources and formally assimilating data with models of ecological processes. The study of infectious disease has depended on strategies for integrating patterns of observed disease incidence with mechanistic process models since John Snow first mapped cholera cases around a London water pump in 1854. Still, zoonotic and vector-borne diseases increasingly affect human populations, and methods used to successfully characterize directly transmitted diseases are often insufficient. We use four case studies to demonstrate that advances in disease forecasting require better understanding of zoonotic host and vector populations, as well of the dynamics that facilitate pathogen amplification and disease spillover into humans. In each case study, this goal is complicated by limited data, spatiotemporal variability in pathogen transmission and impact, and often, insufficient biological understanding. We present a conceptual framework for data-model fusion in infectious disease research that addresses these fundamental challenges using a hierarchical state-space structure to (1) integrate multiple data sources and spatial scales to inform latent parameters, (2) partition uncertainty in process and observation models, and (3) explicitly build upon existing ecological and epidemiological understanding. Given the constraints inherent in the study of infectious disease and the urgent need for progress, fusion of data and expertise via this type of conceptual framework should prove an indispensable tool.

West Nile virus impacts in American crow populations are associated with human land use and climate.

West Nile virus (WNV) was first detected in the western hemisphere during the summer of 1999, reawakening US public awareness of the potential severity of vector-borne pathogens. Since its New World introduction, WNV has caused disease in human, avian, and mammalian communities across the continent. American crows (Corvus brachyrhynchos) are a highly susceptible WNV host and when modeled appropriately, changes in crow abundances can serve as a proxy for the spatio-temporal presence of WNV. We use the dramatic declines in abundance of this avian host to examine spatio-temporal heterogeneity in WNV intensity across the northeastern US, where WNV was first detected. Using data from the Breeding Bird Survey, we identify significant declines in crow abundance after WNV emergence that are associated with lower forest cover, more urban land use, and warmer winter temperatures. Importantly, we document continued declines as WNV was present in an area over consecutive years. Our findings support the urban-pathogen link that human WNV incidence studies have shown. For each 1% increase in urban land cover we expect an additional 5% decline in the log crow abundance beyond the decline attributed to WNV in undeveloped areas. We also demonstrate a significant relationship between above-average winter temperatures and WNV-related declines in crow abundance. The mechanisms behind these patterns remain uncertain and hypotheses requiring further research are suggested. In particular, a strong positive relationship between urban land cover and winter temperatures may confound mechanistic understanding, especially when a temperature-sensitive vector is involved.

Condition-Specific Competitive Effects of the Invasive Mosquito Aedes albopictus on the Resident Culex pipiens among Different Urban Container Habitats May Explain Their Coexistence in the Field.

Condition-specific competition, when environmental conditions alter the outcome of competition, can foster the persistence of resident species after the invasion of a competitively superior invader. We test whether condition-specific competition can facilitate the areawide persistence of the resident and principal West Nile virus vector mosquito Culex pipiens with the competitively superior invasive Aedes albopictus in water from different urban container habitats. (2) Methods: We tested the effects of manipulated numbers of A. albopictus on C. pipiens' survival and development in water collected from common functional and discarded containers in Baltimore, MD, USA. The experiment was conducted with typical numbers of larvae found in field surveys of C. pipiens and A. albopictus and container water quality. (3) Results: We found increased densities of A. albopictus negatively affected the survivorship and development of C. pipiens in water from discarded containers but had little effect in water from functional containers. This finding was driven by water from trash cans, which allowed consistently higher C. pipiens' survival and development and had greater mean ammonia and nitrate concentrations that can promote microbial food than other container types. (4) Conclusions: These results suggest that the contents of different urban containers alter the effects of invasive A. albopictus competition on resident C. pipiens, that trash cans, in particular, facilitate the persistence of C. pipiens, and that there could be implications for West Nile virus risk as a result.

Higher West Nile Virus Infection in Aedes albopictus (Diptera: Culicidae) and Culex (Diptera: Culicidae) Mosquitoes From Lower Income Neighborhoods in Urban Baltimore, MD.

The temperate United States has experienced increasing incidence of mosquito-borne diseases. Recent studies conducted in Baltimore, MD have demonstrated a negative relationship between abundances of Aedes albopictus (Skuse) and Culex mosquitoes and mean neighborhood income level, but have not looked at the presence of pathogens. Mosquitoes collected from five socioeconomically variable neighborhoods were tested for infection by West Nile, chikungunya, and Zika viruses in 2015 and 2016, and again from four of the neighborhoods in 2017. Minimum infection rates of pooled samples were compared among neighborhoods for each year, as well as among individual blocks in 2017. West Nile virus was detected in both Ae. albopictus and Culex pools from all neighborhoods sampled in 2015 and 2017. No infected pools were detected in any year for chikungunya or Zika viruses, and none of the target viruses were detected in 2016. Infection rates were consistently higher for Culex than for Ae. albopictus. Minimum infection rate was negatively associated with mean neighborhood income for both species in 2015. Although earlier work has shown a positive association between block-level abandonment and mosquito abundance, no association was detected in this study. Still, we demonstrate that viral infection in mosquito pools can differ substantially across adjacent urban neighborhoods that vary by income. Though trap security and accessibility often inform city sampling locations, detecting and managing arboviral risk requires surveillance across neighborhoods that vary in socioeconomics, including lower income areas that may be less accessible and secure but have higher infection rates.

Knowledge, Attitude, and Practices Survey in Greece before the Implementation of Sterile Insect Technique against Aedes albopictus.

Community involvement in Aedes albopictus management can be very efficient and result in raising awareness among citizens. Toward this end, a door-to-door campaign can encourage active community participation in vector control. The current study describes the results of an intervention where a KAP (knowledge, attitude, practices) survey tool was paired with a door-to-door campaign and was implemented as an intervention method in Vravrona area (Attica, Greece) before the release of sterile males (sterile insect technique, SIT) against Aedes albopictus. The KAP tool was used to shed light on the knowledge, practices, and attitudes of local community members in order to better prepare and motivate participation in household mosquito control and to assess current understanding of SIT. Each household also received specific information about mosquito source habitat in their own yards at the time of the initial KAP survey. These household data were complemented by standardized mosquito trapping in the municipality. Our findings indicate that citizens' attitude toward SIT ranged from indecisive to fully supportive, while 77.5% of the respondents agreed that the SIT has many advantages over chemical control methods. Furthermore, the results demonstrate that using the door-to-door campaign as an intervention and prerelease method before SIT can suppress the initial mosquito population and potentially improve its efficacy. Lastly, we show that the presence of local municipality officials during door-to-door visits was associated with increased willingness from the residents to participate in the intervention.

Re-assessment of plant carbon dynamics at the Duke free-air CO(2) enrichment site: interactions of atmospheric [CO(2)] with nitrogen and water availability over stand development.

*The potential for elevated [CO(2)]-induced changes to plant carbon (C) storage, through modifications in plant production and allocation of C among plant pools, is an important source of uncertainty when predicting future forest function. Utilizing 10 yr of data from the Duke free-air CO(2) enrichment site, we evaluated the dynamics and distribution of plant C. *Discrepancy between heights measured for this study and previously calculated heights required revision of earlier allometrically based biomass determinations, resulting in higher (up to 50%) estimates of standing biomass and net primary productivity than previous assessments. *Generally, elevated [CO(2)] caused sustained increases in plant biomass production and in standing C, but did not affect the partitioning of C among plant biomass pools. Spatial variation in net primary productivity and its [CO(2)]-induced enhancement was controlled primarily by N availability, with the difference between precipitation and potential evapotranspiration explaining most interannual variability. Consequently, [CO(2)]-induced net primary productivity enhancement ranged from 22 to 30% in different plots and years. *Through quantifying the effects of nutrient and water availability on the forest productivity response to elevated [CO(2)], we show that net primary productivity enhancement by elevated [CO(2)] is not uniform, but rather highly dependent on the availability of other growth resources.

Aedes albopictus Body Size Differs Across Neighborhoods With Varying Infrastructural Abandonment.

Mosquitoes pose an increasing risk in urban landscapes, where spatial heterogeneity in juvenile habitat can influence fine-scale differences in mosquito density and biting activity. We examine how differences in juvenile mosquito habitat along a spectrum of urban infrastructure abandonment can influence the adult body size of the invasive tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae). Adult Ae. albopictus were collected across 3 yr (2015-2017) from residential blocks in Baltimore, MD, that varied in abandonment level, defined by the proportion of houses with boarded-up doors. We show that female Ae. albopictus collected from sites with higher abandonment were significantly larger than those collected from higher income, low abandonment blocks. Heterogeneity in mosquito body size, including wing length, has been shown to reflect differences in important traits, including longevity and vector competence. The present work demonstrates that heterogeneity in female size may reflect juvenile habitat variability across the spatial scales most relevant to adult Aedes dispersal and human exposure risk in urban landscapes. Previous work has shown that failure to manage abandonment and waste issues in impoverished neighborhoods supports greater mosquito production, and this study suggests that mosquitoes in these same neighborhoods could live longer, produce more eggs, and have different vector potential.

Infectious hematopoietic necrosis virus specialization in a multihost salmonid system.

Many pathogens interact and evolve in communities where more than one host species is present, yet our understanding of host-pathogen specialization is mostly informed by laboratory studies with single species. Managing diseases in the wild, however, requires understanding how host-pathogen specialization affects hosts in diverse communities. Juvenile salmonid mortality in hatcheries caused by infectious hematopoietic necrosis virus (IHNV) has important implications for salmonid conservation programs. Here, we evaluate evidence for IHNV specialization on three salmonid hosts and assess how this influences intra- and interspecific transmission in hatchery-reared salmonids. We expect that while more generalist viral lineages should pose an equal risk of infection across host types, viral specialization will increase intraspecific transmission. We used Bayesian models and data from 24 hatcheries in the Columbia River Basin to reconstruct the exposure history of hatcheries with two IHNV lineages, MD and UC, allowing us to estimate the probability of juvenile infection with these lineages in three salmonid host types. Our results show that lineage MD is specialized on steelhead trout and perhaps rainbow trout (both Oncorhynchus mykiss), whereas lineage UC displayed a generalist phenotype across steelhead trout, rainbow trout, and Chinook salmon. Furthermore, our results suggest the presence of specialist-generalist trade-offs because, while lineage UC had moderate probabilities of infection across host types, lineage MD had a small probability of infection in its nonadapted host type, Chinook salmon. Thus, in addition to quantifying probabilities of infection of socially and economically important salmonid hosts with different IHNV lineages, our results provide insights into the trade-offs that viral lineages incur in multihost communities. Our results suggest that knowledge of the specialist/generalist strategies of circulating viral lineages could be useful in salmonid conservation programs to control disease.

The Role of Vector Trait Variation in Vector-Borne Disease Dynamics.

Many important endemic and emerging diseases are transmitted by vectors that are biting arthropods. The functional traits of vectors can affect pathogen transmission rates directly and also through their effect on vector population dynamics. Increasing empirical evidence shows that vector traits vary significantly across individuals, populations, and environmental conditions, and at time scales relevant to disease transmission dynamics. Here, we review empirical evidence for variation in vector traits and how this trait variation is currently incorporated into mathematical models of vector-borne disease transmission. We argue that mechanistically incorporating trait variation into these models, by explicitly capturing its effects on vector fitness and abundance, can improve the reliability of their predictions in a changing world. We provide a conceptual framework for incorporating trait variation into vector-borne disease transmission models, and highlight key empirical and theoretical challenges. This framework provides a means to conceptualize how traits can be incorporated in vector borne disease systems, and identifies key areas in which trait variation can be explored. Determining when and to what extent it is important to incorporate trait variation into vector borne disease models remains an important, outstanding question.