落叶松枯梢病在中国的适生性

落叶松枯梢病(Neofusicoccum laricinum)是威胁落叶松人工林的检疫性林木病害。明确当前该病在中国的潜在适生区及其在未来对气候变化的响应,揭示影响该病害发生流行的主导环境变量,对落叶松枯梢病的早期预警及防治具有重要意义。基于落叶松枯梢病分布数据和环境数据,利用ENMTools、R和刀切法(Jack knife test)筛选分布点数据和环境因子,通过MaxEnt、ArcGIS、SDMTools等技术预测当前和未来气候条件下落叶松枯梢病在中国的潜在适生区,划分病害适生等级并计算各适生等级面积占比,绘制质心转移轨迹。结果表明:(1)建立的落叶松枯梢病在中国的潜在适生区预测模型具有高精确性和可信度(不同年份和不同气候模式下的AUC值均大于0.9);(2)影响落叶松枯梢病分布的主要环境变量为年平均气温、最暖季度降水量、年降水量和最暖季度平均温度;(3)当前气候模式下落叶松枯梢病在中国的潜在适生区面积占中国国土总面积的18.02%,中高适生区集中分布在中国辽宁东南部、吉林东部、黑龙江大部分地区、内蒙古东北部;(4)在三种不同气候条件下(ssp126、ssp245、ssp585),未来落叶松枯梢病在中国的潜在适生区面积与现代气候条件相比均有所减少,其质心由东北向华北、西南地区转移。落叶松枯梢病一旦发生将会造成不可逆的生态灾难和经济损失,因此本研究对落叶松枯梢病在中国的潜在适生区进行预测和分析,研究结果对合理区划落叶松枯梢病潜在入侵风险地、加强重点地区的检疫监测、及时制定有效的防治手段,以及对于发生区的监测和防治与未发生区的早期预警和监管具有重要意义。     

Lodgepole pine forest age class dynamics and susceptibility to mountain pine beetle attack

Because mountain pine beetle attack mature pine stands, an understanding of forest age class dynamics is important to managing forests within the distribution of the beetle. The assumed theoretical negative exponential forest age distribution provides an estimate when ecosystem dynamics are in equilibrium. This study investigates the dynamics of forest age distribution for non-equilibrium ecosystem dynamics, which result primarily from large and irregular stand-replacement fire disturbances that alter the forest age distribution. A model experiment using the SEM-LAND model on a 1 million ha lodgepole pine forest landscape was conducted to estimate how the proportion of susceptible area could be influenced by different fire regimes. The results of the simulation suggest that the temporal dynamics of the area susceptible to mountain pine beetle attack are complex and depend on the fire history of the study area, if the area is experiencing large and irregular stand-replacement fires. The age range of the lodgepole pine forest stands susceptible to mountain pine beetle attack might significantly affect the estimate of the area susceptible to attack.     

Reproductive ecology of Thymelaea velutina (Thymelaeaceae)- Factors contributing to the maintenance of heterocarpy

Thymelaea velutina (Thymelaeaceae) is a dioecious shrub that presents a unique type of heterocarpy which consists of the simultaneous production of dry and fleshy fruits. It is endemic to the Balearic Islands (Western Mediterranean) and is found both in dunes and mountain areas. The goal of this study was to identify which factors influence the production of both fruit types, examining the variation of their effects at a spatio-temporal scale (comparing two localities in different years). Specifically, we investigated (1) whether pollen limitation influences the type of fruit produced, and (2) the possible differences in seed size, mass, dispersal capacity, seed predation, germination patterns and seedling survival between fruit types. We also examined if the production of fleshy fruits was modified with the application of gibberellins to reproductive branches. Although fleshy fruits were consistently more abundant than dry ones at both populations, their proportion was significantly higher at the site with greater precipitation. The addition of either pollen or gibberellins did not affect the proportion of each fruit type. Seeds in fleshy fruits are consistently larger, heavier and more likely to be dispersed than seeds in dry fruits, but germinability, germination rate and seedling survival was similar among fruit types. Heterocarpy in this species is currently maintained as there is no apparent factor that exerts any strong selective pressure on either fruit type. The two fruit types might even have different `functions', one serving especially for dispersal and population expansion and the other for producing a seed bank that ensures an eventual germination.     

Role of antibiotic production by Erwinia herbicola Eh252 in biological control of Erwinia amylovora.

Erwinia herbicola Eh252 is a nonpathogenic epiphytic bacterium that reduces fire blight incidence when sprayed onto apple blossoms before inoculation with Erwinia amylovora, the causal agent of fire blight. Eh252 was found to produce on minimal medium an antibiotic that inhibited the growth of E. amylovora. This antibiotic was inactivated by histidine but not by Fe(II), was sensitive to proteolytic enzymes, and showed a narrow host range of activity. To determine the role of this antibiotic in the control of fire blight, two prototrophic Tn5-induced mutants, 10:12 and 17:12, that had lost their ability to inhibit E. amylovora on plates (Ant- mutants) were compared with the wild-type strain for their ability to suppress fire blight in immature pear fruits. The two mutants had single Tn5 insertions in the chromosome; although they grew in immature pear fruits at a rate similar to that of the wild-type strain, neither of these mutants suppressed fire blight as well as Eh252 did. The Tn5-containing fragment isolated from 10:12 was used to mutagenize Eh252 by marker exchange. Derivatives that acquired the Tn5-containing fragment by homologous recombination lost the ability to inhibit E. amylovora on minimal medium. Furthermore, the three Ant- derivatives tested were also affected in their ability to inhibit E. amylovora in immature pear fruits. The results obtained suggest that antibiotic production is a determinant of the biological control of E. amylovora by Eh252, but that another mechanism(s) is involved.     

Dynamics of Specific Anti-Mycobacterium avium Subsp. paratuberculosis Antibody Response through Age

Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic infection in cattle. MAP infected cattle with humoral immune (HI) reactions with IgG antibodies are usually those where latency of infection has ceased and their infection is progressing towards reduced milk yield, weight loss and significant bacterial excretion in feces. The proportion of detectable infections among all infected animals that will develop disease is often referred to as ‘the tip of the iceberg’. The purpose of this study was to estimate this proportion. Test-records from 18,972 Danish dairy cows with MAP specific IgG antibodies on their final test-record were used to estimate age-specific sensitivities (Se). These cows were the infected ones considered to develop disease in a population with a representative age-distribution and were defined as cases. The specificity (Sp) of the test was estimated based on test-results from 166,905 cows, which had no MAP IgG antibodies in their final four test-records. The Sp, age-specific Se and maximum Se were used to estimate the probability of having HI at a given age resulting in the proportion of infected cows with HI at a given age. For cows 2 years of age, the proportion of detectable cases was 0.33, while it was 0.94 for cows 5 years of age. Thus, there was a significant shift in the tip of the iceberg with aging. This study provided a model for estimating the proportion of latent chronic infections that would progress to disease, and the results can be used to model infection dynamics.     

Identification of Novel Strain-Specific and Environment-Dependent Minor QTLs Linked to Fire Blight Resistance in Apples

Since its first report almost 200 years ago, fire blight, caused by the gram-negative bacterium Erwinia amylovora, has threatened apple and pear production globally. Identifying novel genes and their functional alleles is a prerequisite to developing apple cultivars with enhanced fire blight resistance. Here, we report 13 strain-specific and environment-dependent minor QTLs linked to fire blight resistance from a segregating Malus sieversii × Malus × domestica mapping population. Interval mapping at 95% confidence and Kruskal–Wallis analysis at P value =?0.005 were used to identify QTLs for three strains of E. amylovora differing in virulence and pathogenicity. The QTLs identified explain a small to moderate part of resistance variability, and a majority was not common between years or E. amylovora strains. These QTLs are distributed in eight linkage groups of apples and comparison of their map position to previously identified fire blight resistance QTLs indicates that most are novel loci. Interaction between experimental conditions in the greenhouse and field, and between years, and differences in virulence levels of strains might be responsible for strain- and year-specific QTLs. The QTLs identified on LG10 for strain Ea273 in 2011 and strain LP101 in 2011, and on LG15 for strain LP101 could be the same QTLs identified previously with strain CFBP1430 in cultivar “Florina” and “Co-op16 × Co-op17” mapping population, respectively. We discuss the potential impact of newly identified minor fire blight QTLs and major gene-based resistance on the rate of mutation in pathogen populations to overcome resistance and durability of resistance.     

The effect of spatio-temporal variation in understanding the fruit crop size hypothesis

In order to evaluate the 'fruit crop size' hypothesis, we analyzed the effect of fruit availability on the number of visits by birds and on the proportion of removed fruits, and on how much of the variation in the proportion of removed fruits could be explained by spatio-temporal variability. Fieldwork was done on the coast of the state of Veracruz, Mexico, using the small tree Bursera fagaroides (Burseraceae) and its frugivorous feeding assemblage, on four hills during four years. The number of fruits produced, the number of visits by birds, and the proportion of removed fruits varied between years with more than half an order of magnitude. The number of available fruits was associated to both the number of visits by birds and the proportion of fruits removed from each plant individual, and supports the fruit crop size hypothesis. However, the hypothesis varies in strength depending on total fruit production by the population per year and per hill. The spatio-temporal variation of the system was the effect of variation in the intensity of fructification between years and hills; the inclusion of spatio-temporal variability helped to explain most of the variation found in our results. The latter approach may explain the explain the conflicting results found by other authors in studies done in only one year or at one site, where variation is greatly reduced. Considering the number of published reports, a meta-analysis seems to be in order to determine the existence of a general effect between fruit production, the number of visits by birds and the proportion of fruits removed. If this is possible, we hypothezise that the association between fruit production and the number of visits by birds should be of low intensity.     

Non‐fire induced seed release ina weakly serotinous pine: climatic factors,maintenance costs or both?

The advantages of canopy seed retention (serotiny) for plants inhabiting fire‐prone ecosystems are well documented. However, very few species are completely serotinous and non‐fire induced opening of serotinous fruits is commonly observed (weak serotiny). Two non‐mutually exclusive causes are envisaged to contribute to this process: mechanical changes in serotinous fruits mediated by climatic conditions (e.g. drought) or the costs of maintenance for the plant of these long‐lasting structures. However, their relative contribution to the spontaneous opening of serotinous fruits remains elusive as well as the consequences for the build‐up of the canopy seed bank and inter‐individual differences in serotiny. In this study we monitored the dynamics of cone production and cone opening in the weakly serotinous Pinus halepensis for five years (2004–2008), including two severe drought episodes (2005, 2006). Drought decreased the production of conelets, increased the abortion of immature cones, reduced the seed quality in the cohorts of cones produced during these years, and increased the opening of serotinous cones. During the first drought episode, a higher proportion of serotinous cones opened in those pines bearing a larger crop of younger cones. This suggests that not only passive changes induced by drought but also competition among cones for resources (e.g. water) might be involved in this process. The opening of serotinous cones in pines bearing more cones made inter‐individual differences in the size of the canopy cone bank to narrow or even to reverse from 2004 to 2008. These results may help to understand the decrease in serotiny when pines grow and accumulate more cones and the large inter‐individual variability in the degree of serotiny observed in P. halepensis forests. In addition, the negative effects of drought episodes for the size of the canopy cone bank and the seeds contained can be an unexplored cause of post‐fire regeneration constraint.     

First Report of Erwinia amylovora Fire Blight in Belarus

Erwinia amylovora is a phytopathogenic bacterium that causes fire blight, an economically important disease of Rosaceae . Several isolates from pears and apples with fire blight symptoms from Belarus were identified as E. amylovora . All tested isolates were yellow and mucoid on MM2Cu medium, positive in levan production and showed pathogenicity in immature pear fruits. These isolates have identical total protein patterns with E. amylovora 1/79. The PCR with specific primers for E. amylovora harpin gene also gave positive results.     

Comparison of Bacterial Community of Healthy and Erwinia amylovora Infected Apples

Fire blight disease, caused by Erwinia amylovora, could damage rosaceous plants such as apples, pears, and raspberries. In this study, we designed to understand how E. amylovora affected other bacterial communities on apple rhizosphere; twig and fruit endosphere; and leaf, and fruit episphere. Limited studies on the understanding of the microbial community of apples and changes the community structure by occurrence of the fire blight disease were conducted. As result of these experiments, the infected trees had low species richness and operational taxonomic unit diversity when compared to healthy trees. Rhizospheric bacterial communities were stable regardless of infection. But the communities in endosphere and episphere were significanlty affected by E. amylovora infection. We also found that several metabolic pathways differ significantly between infected and healthy trees. In particular, we observed differences in sugar metabolites. The finding provides that sucrose metabolites are important for colonization of E. amylovora in host tissue. Our results provide fundamental information on the microbial community structures between E. amylovora infected and uninfected trees, which will contribute to developing novel control strategies for the fire blight disease.     

QTL mapping of fire blight resistance in apple

Fire blight caused by the bacterium Erwinia amylovora is a severe threat to apple and pear orchards worldwide. Apple varieties exhibit a wide range of relative susceptibility/tolerance to fire blight. Although, no monogenic resistance against fire blight has been identified yet, recent evidence indicates the existence of quantitative resistance. Potential sources of fire blight resistance include several wild Malus species and some apple cultivars. F1 progenies of ‘Fiesta’בDiscovery’ were inoculated with the Swiss strain Ea 610 and studied under controlled conditions to identify quantitative trait loci (QTLs) for fire blight resistance. Disease was evaluated at four time points after inoculation. Shoot lesion length and the area under disease progress curve (AUDPC) values were used for QTL analysis. One significant (LOD score of 7.5–8.1, p<0.001) QTL was identified on the linkage group 7 of ‘Fiesta’ (F7). The F7 QTL explained about 37.5–38.6% of the phenotypic variation.     

Response of β-Glucosidase to Fungal Infections in Seed, Ovary and Fruit

Localization and changes in the activity of -glucosidase were investigated in wheat caryopsis and glumes infected with Stagonospora nodorum as well as in lily ovaries and harvested tomato fruits both inoculated with Botrytis cinerea. It was established that the pathogen invasion caused splitting of wheat seed coat, xylem blocking in lily carpel and decay in tomato fruits. B. cinerea invasion evoked disorders of the embryogenesis accompanied by a decreased activity of -glucosidase in all ovules. The activity of the enzyme was not changed considerably in wheat seeds as the infection occurred in the late embryonal stages and the embryonal processes were not affected. In the seeds of harvested tomatoes distant from the invaded area the enzyme activity was not changed as well.     

Censoring in an epidemic with an application to hemophilia-associated AIDS

In epidemiologic studies of infectious diseases, the times of infection may be known only up to an interval. A two-stage parametric regression model is proposed for the analysis of cohort studies during an epidemic in which the exact times of infection cannot be ascertained. The methods permit joint estimation of the effects of covariates both on the risk of infection and the risk of progression to clinical disease once infected. The methodology is applied to a cohort of hemophiliacs who were at risk of infection with the AIDS virus. It was found that hemophiliacs with severe Type A hemophilia were at highest risk of infection, and the risk of infection increased sharply in the early 1980s. Hemophiliacs who were over the age of 20 at infection were at higher risk of progression to AIDS than hemophiliacs who were under age 20. The estimate of the cumulative probability of developing AIDS within t years of infection (the incubation period distribution) for hemophiliacs over age 20 was 1 - exp(-.0021t2.516). Since follow-up in this cohort was restricted to about 10 years from infection, estimates of the incubation period distribution beyond 10 years depend on model extrapolation and should be interpreted cautiously.     

Frequent fires alter tree architecture and impair reproduction of a common fire‐tolerant savanna tree

• Several Cerrado tree species have traits and structures that protect from fires. The effectiveness of a trait depends on the fire regime, especially the frequency. We used Vochysia elliptica, a common Cerrado tree, as a model to test whether different fire frequencies alter crown architecture and flower, fruit and seed production.
• We analysed the effect of fire on the production of inflorescences, fruits and seeds, as well as seed germination and tree architecture of 20 trees in each of three plots of a long‐term ecological experiment managed with different fire regimes: burned every 2 years (B), burned every 4 years (Q) in mid‐dry season and an area protected from fire (C).
• We found a large negative effect of fire frequency on crown architecture and on flower and fruit production. Trees in C and Q had significantly more main branches and a larger crown area than trees in B. At its peak, a tree in C was expected to produce 2.4 times more inflorescences than Q, and 15.5 times more than B, with similar magnitudes for fruits. Sixty per cent of trees in B and 10% in Q produced no fruits.
• The differences in architecture might explain the reduction in sexual reproduction due to a smaller physical space to produce flowers at the branch apices. Resource limitation due to plant investment to replace burned vegetative parts may also decrease sexual reproduction. Our results indicate potentially severe consequences of high fire frequencies for population dynamics and species persistence in Cerrado communities.

     

Relationship between Symptom Development and Actual Sites of Infection in Leaves of Anthurium Inoculated with a Bioluminescent Strain of Xanthomonas campestris pv. dieffenbachiae

The infection process of bacterial blight of anthurium was monitored with a bioluminescent strain of Xanthomonas campestris pv. dieffenbachiae. The relationship between symptom expression on infected leaves (assessed visually) and the extent of bacterial movement within tissues (evaluated by bioluminescence emission) varied among anthurium cultivars. In several cultivars previously considered susceptible on the basis of symptom development alone, bacterial invasion of leaves extended far beyond the visually affected areas. In other cultivars previously considered resistant, bacterial invasion was restricted to areas with visible symptoms. In three cultivars previously considered resistant, leaves were extensively invaded by the bacterium, and yet few or no symptoms were seen on infected leaves. The pathogen was consistently recovered from leaf sections emitting bioluminescence but not from sections emitting no light. At an early stage of infection, no significant differences in the percentages of infected areas as determined by visual assessment were observed in any of the cultivars. However, differences among cultivars were detected by bioluminescence as the disease progressed, because bacterial invasion was not always accompanied by symptom expression. In susceptible cultivars, the advancing border of infection was 5 to 10 cm inward from the margins of the visible symptoms and often reached to the leaf petiole even when symptoms were visible in <10% of the total leaf area. Comparisons of anthurium cultivars in which a nondestructive method was used to quantify the severity of leaf infection by a bioluminescent pathogen have enabled us to evaluate susceptibility and resistance to bacterial blight accurately. Such evaluations will be of importance in breeding resistant cultivars for disease control.     

Relative importance of host plant patch geometry and habitat quality on the patterns of occupancy,extinction and density of the monophagous butterfly <Emphasis Type="Italic">Iolana iolas</Emphasis>

Habitat fragmentation is a major cause of species rarity and decline because it increases local population extinctions and reduces recolonisation rates of remnant patches. Although two major patch characteristics (area and connectivity) have been used to predict distribution patterns in fragmented landscapes, other factors can affect the occurrence of a species as well as the probability of it becoming extinct. In this paper, we study the spatial structure and dynamics of the butterfly Iolana iolas in a 75-patch network of its host plant (Colutea hispanica) to determine the relative importance of patch area, connectivity and habitat quality characteristics on occupancy, extinction and density over the period 2003–2006. Occupancy in 2003, incidence (proportion of years occupied) and probability of extinction were mostly affected by patch area. Smaller patches were less likely to be occupied because they had a higher probability of extinction, partly due to environmental stochasticity. The density of I. iolas was negatively related to patch area in all study years. Only in 2004 was the density of I. iolas positively influenced by fruit production per plant. Our results suggest that for I. iolas, and probably for other specialist butterflies with clearly delimited resource requirements, metapopulation dynamics can be satisfactorily predicted using only geometric variables because most habitat characteristics are subsumed in patch area. However, this hypothesis should be subject to further testing under diverse environmental conditions to evaluate the extent of its generalisation.     

Using the Prevalence of Individual Species of Intestinal Nematode Worms to Estimate the Combined Prevalence of Any Species

Objectives

To assess if a probabilistic model could be used to estimate the combined prevalence of infection with any species of intestinal nematode worm when only the separate prevalence of each species is reported, and to estimate the extent to which simply taking the highest individual species prevalence underestimates the combined prevalence.

Methods

Data were extracted from community surveys that reported both the proportion infected with individual species and the combined proportion infected, for a minimum sample of 100 individuals. The predicted combined proportion infected was calculated based on the assumption that the probability of infection with one species was independent of infection with another species, so the probability of combined infections was multiplicative.

Findings

Thirty-three reports describing 63 data sets from surveys conducted in 20 countries were identified. A strong correlation was found between the observed and predicted combined proportion infected (r = 0.996, P<0.001). When the observed and predicted values were plotted against each other, a small correction of the predicted combined prevalence by dividing by a factor of 1.06 achieved a near perfect correlation between the two sets of values. The difference between the single highest species prevalence and the observed combined prevalence was on average 7% or smaller at a prevalence of ≤40%, but at prevalences of 40–80%, the difference was about 12%.

Conclusions

A simple probabilistic model of combined infection with a small correction factor is proposed as a novel method to estimate the number of individuals that would benefit from mass deworming when data are reported only for separate species.     

Characterizing interannual variations in global fire calendar using data from Earth observing satellites

Daily global observations from the Advanced Very High‐Resolution Radiometers on the series of meteorological satellites operated by the National Oceanic and Atmospheric Administration between 1982 and 1999 were used to generate a new weekly global burnt surface product at a resolution of 8 km. Comparison with independently available information on fire locations and timing suggest that while the time‐series cannot yet be used to make accurate and quantitative estimates of global burnt area it does provide a reliable estimate of changes in location and season of burning on the global scale. This time‐series was used to characterize fire activity in both northern and southern hemispheres on the basis of average seasonal cycle and interannual variability. Fire seasonality and fire distribution data sets have been combined to provide gridded maps at 0.5° resolution documenting the probability of fire occurring in any given season for any location. A multiannual variogram constructed from 17 years of observations shows good agreement between the spatial–temporal behavior in fire activity and the ‘El Niño’ Southern Oscillation events, showing highly likely connections between both phenomena.     

Estimating infection prevalence: Best practices and their theoretical underpinnings

Accurately estimating infection prevalence is fundamental to the study of population health, disease dynamics, and infection risk factors. Prevalence is estimated as the proportion of infected individuals (“individual‐based estimation”), but is also estimated as the proportion of samples in which evidence of infection is detected (“anonymous estimation”). The latter method is often used when researchers lack information on individual host identity, which can occur during noninvasive sampling of wild populations or when the individual that produced a fecal sample is unknown. The goal of this study was to investigate biases in individual‐based versus anonymous prevalence estimation theoretically and to test whether mathematically derived predictions are evident in a comparative dataset of gastrointestinal helminth infections in nonhuman primates. Using a mathematical model, we predict that anonymous estimates of prevalence will be lower than individual‐based estimates when (a) samples from infected individuals do not always contain evidence of infection and/or (b) when false negatives occur. The mathematical model further predicts that no difference in bias should exist between anonymous estimation and individual‐based estimation when one sample is collected from each individual. Using data on helminth parasites of primates, we find that anonymous estimates of prevalence are significantly and substantially (12.17%) lower than individual‐based estimates of prevalence. We also observed that individual‐based estimates of prevalence from studies employing single sampling are on average 6.4% higher than anonymous estimates, suggesting a bias toward sampling infected individuals. We recommend that researchers use individual‐based study designs with repeated sampling of individuals to obtain the most accurate estimate of infection prevalence. Moreover, to ensure accurate interpretation of their results and to allow for prevalence estimates to be compared among studies, it is essential that authors explicitly describe their sampling designs and prevalence calculations in publications.     

Double-observer approach to estimating egg mass abundance of pool-breeding amphibians

Interest in seasonally flooded pools, and the status of associated amphibian populations, has initiated programs in the northeastern United States to document and monitor these habitats. Counting egg masses is an effective way to determine the population size of pool-breeding amphibians, such as wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum). However, bias is associated with counts if egg masses are missed. Counts unadjusted for the proportion missed (i.e., without adjustment for detection probability) could lead to false assessments of population trends. We used a dependent double-observer method in 2002–2003 to estimate numbers of wood frog and spotted salamander egg masses at seasonal forest pools in 13 National Wildlife Refuges, 1 National Park, 1 National Seashore, and 1 State Park in the northeastern United States. We calculated detection probabilities for egg masses and examined whether detection probabilities varied by species, observers, pools, and in relation to pool characteristics (pool area, pool maximum depth, within-pool vegetation). For the 2 years, model selection indicated that no consistent set of variables explained the variation in data sets from individual Refuges and Parks. Because our results indicated that egg mass detection probabilities vary spatially and temporally, we conclude that it is essential to use estimation procedures, such as double-observer methods with egg mass surveys, to determine population sizes and trends of these species.