scholarly journals Complex effects of non-host diversity on the removal of free-living infective stages of parasites

2020 ◽  
Author(s):  
Jennifer Welsh ◽  
Mirjana Markovic ◽  
David Thieltges ◽  
Jaap van der Meer
Keyword(s):  
Aquatic Ecosystems ◽  
Disease Risk ◽  
Interspecific Interactions ◽  
Community Diversity ◽  
Ecological Communities ◽  
Free Living ◽  
Surface Design ◽  
Host Diversity ◽  
Transmission Pathways ◽  
Diversity Effects

Ecological communities can affect transmission pathways of parasites and pathogens, ultimately affecting disease dynamics. While the community composition of less competent decoy hosts is known to affect diseases in focal hosts, it remains poorly understood whether such diversity effects also exist when non-host organisms remove free-living parasite stages, e.g. by predation. In response surface design laboratory experiments, we investigated non-host diversity effects on the removal of cercarial stages of trematodes, ubiquitous parasites in aquatic ecosystems. In all three combinations of two non-hosts at four density levels, the addition of a second non-host did not generally result in increased parasite removal but neutralised, amplified or reduced the parasite removal exerted by the first non-host, depending on the density. These complex non-host diversity effects were probably driven by intra- and interspecific interactions and suggest the need to integrate non-host diversity effects in understanding the links between community diversity and disease risk.

scholarly journals Interaction capacity underpins community diversity

2020 ◽  
Author(s):  
Masayuki Ushio
Keyword(s):  
Interspecific Interactions ◽  
Experimental Studies ◽  
Interaction Strength ◽  
Single Species ◽  
Species Interaction ◽  
Community Diversity ◽  
Ecological Communities ◽  
Total Dna ◽  
Mathematical Equations ◽  
The Mean

AbstractHow patterns in community diversity emerge is a long-standing question in ecology. Theories and experimental studies suggested that community diversity and interspecific interactions are interdependent. However, evidence from multitaxonomic, high-diversity ecological communities is lacking because of practical challenges in characterizing speciose communities and their interactions. Here, I analyzed time-varying causal interaction networks that were reconstructed using 1197 species, DNA-based ecological time series taken from experimental rice plots and empirical dynamic modeling, and show that species interaction capacity, namely, the sum of interaction strength that a single species gives and receives, underpins community diversity. As community diversity increases, the number of interactions increases exponentially but the mean species interaction capacity of a community becomes saturated, weakening interaction among species. These patterns are explicitly modeled with simple mathematical equations, based on which I propose the “interaction capacity hypothesis”, namely, that species interaction capacity and network connectance are proximate drivers of community diversity. Furthermore, I show that total DNA concentrations and temperature influence species interaction capacity and connectance nonlinearly, explaining a large proportion of diversity patterns observed in various systems. The interaction capacity hypothesis enables mechanistic explanations of community diversity, and how species interaction capacity is determined is a key question in ecology.

Climate-associated trends and variability in ichthyoplankton phenology from the longest continuous larval fish time series on the east coast of the United States

2020 ◽  
Vol 650 ◽  
pp. 269-287
Author(s):  
WC Thaxton ◽  
JC Taylor ◽  
RG Asch
Keyword(s):  
United States ◽  
Environmental Variability ◽  
Larval Fish ◽  
Interspecific Interactions ◽  
River Estuary ◽  
Atlantic Multidecadal Oscillation ◽  
The United States ◽  
Larval Survival ◽  
Ecological Communities ◽  
Northerly Wind

As the effects of climate change become more pronounced, variation in the direction and magnitude of shifts in species occurrence in space and time may disrupt interspecific interactions in ecological communities. In this study, we examined how the fall and winter ichthyoplankton community in the Newport River Estuary located inshore of Pamlico Sound in the southeastern United States has responded to environmental variability over the last 27 yr. We relate the timing of estuarine ingress of 10 larval fish species to changes in sea surface temperature (SST), the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, wind strength and phenology, and tidal height. We also examined whether any species exhibited trends in ingress phenology over the last 3 decades. Species varied in the magnitude of their responses to all of the environmental variables studied, but most shared a common direction of change. SST and northerly wind strength had the largest impact on estuarine ingress phenology, with most species ingressing earlier during warm years and delaying ingress during years with strong northerly winds. As SST warms in the coming decades, the average date of ingress of some species (Atlantic croaker Micropogonias undulatus, summer flounder Paralichthys dentatus, pinfish Lagodon rhomboides) is projected to advance on the order of weeks to months, assuming temperatures do not exceed a threshold at which species can no longer respond through changes in phenology. These shifts in ingress could affect larval survival and growth since environmental conditions in the estuarine and pelagic nursery habitats of fishes also vary seasonally.

scholarly journals Host Diversity and Potential Transmission Pathways of SARS-CoV-2 at the Human-Animal Interface

Pathogens ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 180 ◽  
Author(s):  
Hayden D. Hedman ◽  
Eric Krawczyk ◽  
Yosra A. Helmy ◽  
Lixin Zhang ◽  
Csaba Varga
Keyword(s):  
Public Health ◽  
Close Contact ◽  
Natural Infection ◽  
Emerging Infectious Diseases ◽  
Reservoir Host ◽  
Host Susceptibility ◽  
Public Health Issue ◽  
Severe Illness ◽  
Host Diversity ◽  
Transmission Pathways

Emerging infectious diseases present great risks to public health. The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19), has become an urgent public health issue of global concern. It is speculated that the virus first emerged through a zoonotic spillover. Basic research studies have suggested that bats are likely the ancestral reservoir host. Nonetheless, the evolutionary history and host susceptibility of SARS-CoV-2 remains unclear as a multitude of animals has been proposed as potential intermediate or dead-end hosts. SARS-CoV-2 has been isolated from domestic animals, both companion and livestock, as well as in captive wildlife that were in close contact with human COVID-19 cases. Currently, domestic mink is the only known animal that is susceptible to a natural infection, develop severe illness, and can also transmit SARS-CoV-2 to other minks and humans. To improve foundational knowledge of SARS-CoV-2, we are conducting a synthesis review of its host diversity and transmission pathways. To mitigate this COVID-19 pandemic, we strongly advocate for a systems-oriented scientific approach that comprehensively evaluates the transmission of SARS-CoV-2 at the human and animal interface.

Diversifying forest communities may change Lyme disease risk: extra dimension to the dilution effect in Europe

Parasitology ◽  
2016 ◽  
Vol 143 (10) ◽  
pp. 1310-1319 ◽  
Author(s):  
SANNE C. RUYTS ◽  
EVY AMPOORTER ◽  
ELENA C. COIPAN ◽  
LANDER BAETEN ◽  
DIETER HEYLEN ◽  
...  
Keyword(s):  
North America ◽  
Lyme Disease ◽  
Borrelia Burgdorferi ◽  
Disease Risk ◽  
Severe Disease ◽  
Dilution Effect ◽  
Ixodid Ticks ◽  
Infection Prevalence ◽  
Host Diversity ◽  
Pine Stands

SUMMARYLyme disease is caused by bacteria of theBorrelia burgdorferigenospecies complex and transmitted by Ixodid ticks. In North America only one pathogenic genospecies occurs, in Europe there are several. According to the dilution effect hypothesis (DEH), formulated in North America, nymphal infection prevalence (NIP) decreases with increasing host diversity since host species differ in transmission potential. We analysedBorreliainfection in nymphs from 94 forest stands in Belgium, which are part of a diversification gradient with a supposedly related increasing host diversity: from pine stands without to oak stands with a shrub layer. We expected changing tree species and forest structure to increase host diversity and decrease NIP. In contrast with the DEH, NIP did not differ between different forest types. Genospecies diversity however, and presumably also host diversity, was higher in oak than in pine stands. Infected nymphs tended to harbourBorrelia afzeliiinfection more often in pine stands whileBorrelia gariniiandBorrelia burgdorferiss. infection appeared to be more prevalent in oak stands. This has important health consequences, since the latter two cause more severe disease manifestations. We show that the DEH must be nuanced for Europe and should consider the response of multiple pathogenic genospecies.

scholarly journals ToxigenicVibrio choleraeevolution and establishment of reservoirs in aquatic ecosystems

2020 ◽  
Vol 117 (14) ◽  
pp. 7897-7904 ◽  
Author(s):  
Carla Mavian ◽  
Taylor K. Paisie ◽  
Meer T. Alam ◽  
Cameron Browne ◽  
Valery Madsen Beau De Rochars ◽  
...  
Keyword(s):  
Aquatic Ecosystems ◽  
Indian Subcontinent ◽  
Population Bottlenecks ◽  
Direct Transmission ◽  
Term Survival ◽  
Bacterial Transmission ◽  
Transmission Pathways ◽  
Robust Evidence

The spread of cholera in the midst of an epidemic is largely driven by direct transmission from person to person, although it is well-recognized thatVibrio choleraeis also capable of growth and long-term survival in aquatic ecosystems. While prior studies have shown that aquatic reservoirs are important in the persistence of the disease on the Indian subcontinent, an epidemiological view postulating that locally evolving environmentalV. choleraecontributes to outbreaks outside Asia remains debated. The single-source introduction of toxigenicV. choleraeO1 in Haiti, one of the largest outbreaks occurring this century, with 812,586 suspected cases and 9,606 deaths reported through July 2018, provided a unique opportunity to evaluate the role of aquatic reservoirs and assess bacterial transmission dynamics across environmental boundaries. To this end, we investigated the phylogeography of both clinical and aquatic toxigenicV. choleraeO1 isolates and show robust evidence of the establishment of aquatic reservoirs as well as ongoing evolution ofV. choleraeisolates from aquatic sites. Novel environmental lineages emerged from sequential population bottlenecks, carrying mutations potentially involved in adaptation to the aquatic ecosystem. Based on such empirical data, we developed a mixed-transmission dynamic model ofV. cholerae, where aquatic reservoirs actively contribute to genetic diversification and epidemic emergence, which underscores the complexity of transmission pathways in epidemics and endemic settings and the need for long-term investments in cholera control at both human and environmental levels.

scholarly journals The Effects of Host Diversity and Other Management Components on Epidemics of Potato Late Blight in the Humid Highland Tropics

2001 ◽  
Vol 91 (10) ◽  
pp. 993-1000 ◽  
Author(s):  
K. A. Garrett ◽  
R. J. Nelson ◽  
C. C. Mundt ◽  
G. Chacón ◽  
R. E. Jaramillo ◽  
...  
Keyword(s):  
Late Blight ◽  
Potato Production ◽  
Potato Late Blight ◽  
Planting Density ◽  
Susceptible Host ◽  
Host Diversity ◽  
Progress Curve ◽  
Commercial Potato ◽  
Diversity Effect ◽  
Diversity Effects

A field study at three highland sites near Quito, Ecuador, was conducted to determine whether host-diversity effects on potato late blight would be as important as recently found in studies conducted in temperate areas. We compared three potato mixtures and use of mixtures in combination with different planting densities and two fungicide regimes. Treatment comparisons were made by absolute and relative measures of host-diversity effects and incorporating a truncated area under the disease progress curve as a means of standardizing comparisons across sites. Potato-faba intercrops consisting of only 10% potato provided an estimate of the effects of dilution of susceptible host tissue. Host-diversity effects were very different across study sites, with a large host-diversity effect for reduced disease only at the site most distant from commercial potato production. Planting density had little influence on host-diversity effects or on late blight in single-genotype stands. Fungicide use in combination with potato mixtures enhanced a host-diversity effect for reduced late blight. Potato-faba intercrops produced only a small decrease in potato late blight. Effects of host diversity on yield were variable, with the greatest increase in yield for mixtures treated with fungicides at the site most distant from commercial potato production. The effects of host diversity on late blight severity may be less consistent in the tropical highlands than in the temperate zone, but can contribute to integrated disease management.

scholarly journals Temporal Changes in Archaeal Diversity and Chemistry in a Mid-Ocean Ridge Subseafloor Habitat

2002 ◽  
Vol 68 (4) ◽  
pp. 1585-1594 ◽  
Author(s):  
Julie A. Huber ◽  
David A. Butterfield ◽  
John A. Baross
Keyword(s):  
Microbial Community ◽  
Hydrothermal Systems ◽  
Community Diversity ◽  
Most Probable Number ◽  
Rrna Gene ◽  
Archaeal Diversity ◽  
Free Living ◽  
Probable Number ◽  
Diffuse Flow ◽  
Group I

ABSTRACT The temporal variation in archaeal diversity in vent fluids from a midocean ridge subseafloor habitat was examined using PCR-amplified 16S rRNA gene sequence analysis and most-probable-number (MPN) cultivation techniques targeting hyperthermophiles. To determine how variations in temperature and chemical characteristics of subseafloor fluids affect the microbial communities, we performed molecular phylogenetic and chemical analyses on diffuse-flow vent fluids from one site shortly after a volcanic eruption in 1998 and again in 1999 and 2000. The archaeal population was divided into particle-attached (>3-μm-diameter cells) and free-living fractions to test the hypothesis that subseafloor microorganisms associated with active hydrothermal systems are adapted for a lifestyle that involves attachment to solid surfaces and formation of biofilms. To delineate between entrained seawater archaea and the indigenous subseafloor microbial community, a background seawater sample was also examined and found to consist only of Group I Crenarchaeota and Group II Euryarchaeota, both of which were also present in vent fluids. The indigenous subseafloor archaeal community consisted of clones related to both mesophilic and hyperthermophilic Methanococcales, as well as many uncultured Euryarchaeota, some of which have been identified in other vent environments. The particle-attached fraction consistently showed greater diversity than the free-living fraction. The fluid and MPN counts indicate that while culturable hyperthermophiles represent less than 1% of the total microbial community, the subseafloor at new eruption sites does support a hyperthermophilic microbial community. The temperature and chemical indicators of the degree of subseafloor mixing appear to be the most important environmental parameters affecting community diversity, and it is apparent that decreasing fluid temperatures correlated with increased entrainment of seawater, decreased concentrations of hydrothermal chemical species, and increased incidence of seawater archaeal sequences.

scholarly journals Climate-driven diversity loss in a grassland community

2015 ◽  
Vol 112 (28) ◽  
pp. 8672-8677 ◽  
Author(s):  
Susan P. Harrison ◽  
Elise S. Gornish ◽  
Stella Copeland
Keyword(s):  
Local Community ◽  
N Deposition ◽  
Livestock Grazing ◽  
Community Diversity ◽  
Ecological Communities ◽  
Grassland Community ◽  
Climatic Trends ◽  
Lower Productivity ◽  
California Grassland ◽  
Grazing History

Local ecological communities represent the scale at which species coexist and share resources, and at which diversity has been experimentally shown to underlie stability, productivity, invasion resistance, and other desirable community properties. Globally, community diversity shows a mixture of increases and decreases over recent decades, and these changes have relatively seldom been linked to climatic trends. In a heterogeneous California grassland, we documented declining plant diversity from 2000 to 2014 at both the local community (5 m2) and landscape (27 km2) scales, across multiple functional groups and soil environments. Communities became particularly poorer in native annual forbs, which are present as small seedlings in midwinter; within native annual forbs, community composition changed toward lower representation of species with a trait indicating drought intolerance (high specific leaf area). Time series models linked diversity decline to the significant decrease in midwinter precipitation. Livestock grazing history, fire, succession, N deposition, and increases in exotic species could be ruled out as contributing causes. This finding is among the first demonstrations to our knowledge of climate-driven directional loss of species diversity in ecological communities in a natural (nonexperimental) setting. Such diversity losses, which may also foreshadow larger-scale extinctions, may be especially likely in semiarid regions that are undergoing climatic trends toward higher aridity and lower productivity.

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