scholarly journals The Effect of Landscape Pattern on the Optimal Eradication Zone of an Invading Epidemic

2010 ◽  
Vol 100 (7) ◽  
pp. 638-644 ◽  
Author(s):  
S. Parnell ◽  
T. R. Gottwald ◽  
C. A. Gilligan ◽  
N. J. Cunniffe ◽  
F. van den Bosch
Keyword(s):  
Landscape Pattern ◽  
Plant Pathogens ◽  
Spatial Configuration ◽  
Host Population ◽  
Practical Significance ◽  
Spatially Explicit ◽  
High Profile ◽  
Eradication Campaign ◽  
Level Of Aggregation ◽  
Optimal Radius

A number of high profile eradication attempts on plant pathogens have recently been attempted in response to the increasing number of introductions of economically significant nonnative pathogen species. Eradication programs involve the removal of a large proportion of a host population and can thus lead to significant social and economic costs. In this paper we use a spatially explicit stochastic model to simulate an invading pathogen and show that it is possible to identify an optimal control radius, i.e., one that minimizes the total number of hosts removed during an eradication campaign that is effective in eradicating the pathogen. However, by simulating the epidemic and eradication processes in multiple landscapes, we demonstrate that the optimal radius depends critically on landscape pattern (i.e., the spatial configuration of hosts within the landscape). In particular, we find that the optimal radius, and also the number of host removals associated with it, increases with both the level of aggregation and the density of hosts in the landscape. The result is of practical significance and demonstrates that the location of an invading epidemic should be a key consideration in the design of future eradication strategies.

A spatially explicit agent-based model of central place foraging theory and its explanatory power for hunter-gatherers settlement patterns formation processes

2020 ◽  
Vol 28 (5) ◽  
pp. 377-397 ◽  
Author(s):  
Kaarel Sikk ◽  
Geoffrey Caruso
Keyword(s):  
Settlement Patterns ◽  
Spatial Configuration ◽  
Explanatory Power ◽  
Central Place ◽  
Spatially Explicit ◽  
Formation Processes ◽  
Central Place Foraging ◽  
Hunter Gatherers ◽  
Agent Based ◽  
Settlement Location

The behavioural ecological approach to anthropology states that the density and distribution of resources determines optimal patterns of resource use and also sets its constraints to grouping, mobility and settlement choice. Central place foraging (CPF) models have been used for analyzing foraging behaviours of hunter-gatherers and drawing a causal link from the volume of available resources in the environment to the mobility decisions of hunter-gatherers. In this study, we propose a spatially explicit agent-based CPF model. We explore its potential for explaining the formation of settlement patterns and test its robustness to the configuration of space. Building on a model assuming homogeneous energy distributions, we had to add several new parameters and an adaptation mechanism for foragers to predict the length of their stay, together with a heterogeneous environment configuration. The validation of the model shows that the spatially explicit CPF is generally robust to spatial configuration of energy resources. The total volume of energy has a significant effect on constraining sedentism as predicted by aspatial model and thus can be used on different environmental conditions. Still the spatial autocorrelation of resource distribution has a linear effect on optimal mobility decisions and needs to be considered in predictive models. The effect on settlement location choice is not substantial and is more determined by other characteristics of settlement location. This limits the CPF models in analyzing settlement pattern formation processes.

scholarly journals Lions, Bylaws, and Conservation Metrics

BioScience ◽  
2019 ◽  
Author(s):  
Monique Borgerhoff Mulder ◽  
Jonathan Lucas Kwiyega ◽  
Simone Beccaria ◽  
Sylvester Sadock Bwasama ◽  
Emily Fitzherbert ◽  
...  
Keyword(s):  
Project Managers ◽  
Practical Significance ◽  
High Profile ◽  
Wildlife Conflict ◽  
Wide Scale ◽  
Novel Strategy ◽  
Conservation Organizations ◽  
Number Of Individuals ◽  
African Lions ◽  
Human Wildlife Conflict

Abstract African lions are a significant threat to pastoralists, triggering both retaliatory and nonretaliatory killings that represent a high-profile example of human–wildlife conflict. In the present article, we report on a grassroots campaign to reduce such conflict by shifting agropastoralists’ attitudes toward lion killing and the central role of bylaws in its apparent success. Insofar as all of East Africa's principal protected areas still harboring lions are surrounded by pastoralist populations, the vast majority of which persecute lions, this novel strategy is of considerable wide-scale and practical significance. We report on an estimated 59%–69% reduction in the number of lions killed since the implementation of bylaws and use our experiences to highlight the need for fresh dialog among project managers, conservation organizations, and their funders in crafting appropriate conservation success metrics. In the context of human–wildlife conflict, changes in peoples’ norms and attitudes are of greater significance over the long term than simplistic tabulations of the number of individuals saved.

scholarly journals The Basic Reproduction Number of Plant Pathogens: Matrix Approaches to Complex Dynamics

2008 ◽  
Vol 98 (2) ◽  
pp. 239-249 ◽  
Author(s):  
F. van den Bosch ◽  
N. McRoberts ◽  
F. van den Berg ◽  
L. V. Madden
Keyword(s):  
Basic Reproduction Number ◽  
Plant Pathogens ◽  
Complex Dynamics ◽  
Reproduction Number ◽  
Infected Individual ◽  
Host Population ◽  
Matrix Population Models ◽  
Wide Range ◽  
Simple Systems ◽  
The Basic Reproduction Number

The basic reproduction number, R0, is defined as the total number of infections arising from one newly infected individual introduced into a healthy (disease-free) host population. R0 is widely used in ecology and animal and human epidemiology, but has received far less attention in the plant pathology literature. Although the calculation of R0 in simple systems is straightforward, the calculation in complex situations is challenging. A very generic framework exists in the mathematical and biomathematical literature, which is difficult to interpret and apply in specific cases. In this paper we describe a special case of this general framework involving the use of matrix population models. Leading by example, we explain the existing mathematical literature on this subject in such a way that plant pathologists can apply the method for a wide range of pathosystems.

scholarly journals Sampling for disease absence—deriving informed monitoring from epidemic traits

2018 ◽  
Author(s):  
Yoann Bourhis ◽  
Timothy R. Gottwald ◽  
Francisco J. Lopez-Ruiz ◽  
Sujin Patarapuwadol ◽  
Frank van den Bosch
Keyword(s):  
Infectious Diseases ◽  
Probability Density ◽  
Bacterial Blight ◽  
Plant Pathogens ◽  
Statistical Approach ◽  
Fundamental Property ◽  
Grey Mould ◽  
Citrus Canker ◽  
Host Population ◽  
Sampling Effort

AbstractMonitoring for disease requires subsets of the host population to be sampled and tested for the pathogen. If all the samples return healthy, what are the chances the disease was present but missed? In this paper, we developed a statistical approach to solve this problem considering the fundamental property of infectious diseases: their growing incidence in the host population. The model gives an estimate of the incidence probability density as a function of the sampling effort, and can be reversed to derive adequate monitoring patterns ensuring a given maximum incidence in the population. We then present an approximation of this model, providing a simple rule of thumb for practitioners. The approximation is shown to be accurate for a sample size larger than 20, and we demonstrate its use by applying it to three plant pathogens: citrus canker, bacterial blight and grey mould.

scholarly journals Population biology of multispecies helminth infection: interspecific interactions and parasite distribution

Parasitology ◽  
2005 ◽  
Vol 131 (3) ◽  
pp. 417-433 ◽  
Author(s):  
C. BOTTOMLEY ◽  
V. ISHAM ◽  
M.-G. BASÁÑEZ
Keyword(s):  
Population Biology ◽  
Deterministic Model ◽  
Synergistic Effects ◽  
Interspecific Interactions ◽  
Interspecific Interaction ◽  
Host Population ◽  
Helminth Species ◽  
Age Classes ◽  
Level Of Aggregation ◽  
Positive Correlations

Despite evidence for the existence of interspecific interactions between helminth species, there has been no theoretical exploration of their effect on the distribution of the parasite species in a host population. We use a deterministic model for the accumulation and loss of adult worms of 2 interacting helminth species to motivate an individual-based stochastic model. The mean worm burden and variance[ratio ]mean ratio (VMR) of each species, and the correlation between the two species are used to describe the distribution within different host age classes. We find that interspecific interactions can produce convex age-intensity profiles and will impact the level of aggregation (as measured by the VMR). In the absence of correlated exposure, the correlation in older age classes may be close to zero when either intra- or interspecific synergistic effects are strong. We therefore suggest examining the correlation between species in young hosts as a possible means of identifying interspecific interaction. The presence of correlation between the rates of exposure makes the interpretation of correlations between species more difficult. Finally we show that in the absence of interaction, strong positive correlations are generated by averaging across most age classes.

Steady state concentration for a phenotypic structured problem modeling the evolutionary epidemiology of spore producing pathogens

2017 ◽  
Vol 27 (02) ◽  
pp. 385-426 ◽  
Author(s):  
Ramses Djidjou-Demasse ◽  
Arnaud Ducrot ◽  
Frédéric Fabre
Keyword(s):  
Steady State ◽  
Existence And Uniqueness ◽  
Spectral Properties ◽  
Plant Pathogens ◽  
Adaptive Dynamics ◽  
Host Population ◽  
Steady State Concentration ◽  
Evolutionary Epidemiology ◽  
Concentration Properties ◽  
State Concentration

In this paper, we construct a model to describe the evolutionary epidemiology of spore producing asexual plant pathogens in a homogeneous host population. By considering the evolution in the space of the pathogen phenotypic values, we derive an integro-differential equation with nonlocal mutation terms. Our first main result is concerned with the existence and uniqueness of the endemic steady state of the model. Next assuming that the mutation kernel depends on a small parameter [Formula: see text] (the variance of the dispersion into the space of the pathogen phenotypic values), we investigate the concentration properties of the endemic steady state in the space of phenotypic values. In the context of this work, several Evolutionary Attractors (EAs) (as defined in classical adaptive dynamics) may exist. However, in rather general situations, our results show that only one EA persists when the populations are at equilibrium and when [Formula: see text] is small enough. Our analysis strongly relies on a refined description of the spectral properties of some integral operator with a highly concentrated kernel. We conclude the paper by presenting some numerical simulations of the model to illustrate this concentration phenomenon.

scholarly journals Large-Scale Fungicide Spray Heterogeneity and the Regional Spread of Resistant Pathogen Strains

2006 ◽  
Vol 96 (5) ◽  
pp. 549-555 ◽  
Author(s):  
S. Parnell ◽  
F. van den Bosch ◽  
C. A. Gilligan
Keyword(s):  
Resistant Strain ◽  
Large Scale ◽  
Plant Pathogens ◽  
Regional Scale ◽  
Management Strategies ◽  
Resistance Management ◽  
Reproductive Capacity ◽  
Practical Significance ◽  
Free Fields ◽  
Disease Free

Most models for the spread of fungicide resistance in plant pathogens are focused on within-field dynamics, yet regional invasion depends upon the interactions between field populations. Here, we use a spatially implicit metapopulation model to describe the dynamics of regional spread, in which subpopulations correspond to single fields. We show that the criterion for the regional invasion of pathogens between fields differs from that for invasion within fields. That is, the ability of a fungicide-resistant strain of a pathogen to invade a field population does not necessarily imply an ability to spread through many fields at the regional scale. This depends upon an interaction between the fraction of fields that is sprayed and the reproductive capacity of the pathogen. This result is of practical significance and indicates that resistance management strategies which currently target within-field processes, such as the use of mixtures and alternations of fungicides, may be more effective if between-field processes also were targeted; for example, through the restricted deployment of fungicides over large areas. We also show that the fraction of disease-free fields is maximized when the proportion of fields that is sprayed is just below the threshold for invasion of the resistant strain.

scholarly journals Spatial patterns of agricultural expansion determine impacts on biodiversity and carbon storage

2015 ◽  
Vol 112 (24) ◽  
pp. 7402-7407 ◽  
Author(s):  
Rebecca Chaplin-Kramer ◽  
Richard P. Sharp ◽  
Lisa Mandle ◽  
Sarah Sim ◽  
Justin Johnson ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Carbon Storage ◽  
Large Scale ◽  
Spatial Configuration ◽  
Land Development ◽  
Spatially Explicit ◽  
Agricultural Expansion ◽  
Land Conversion ◽  
Product Demand ◽  
Explicit Analysis

The agricultural expansion and intensification required to meet growing food and agri-based product demand present important challenges to future levels and management of biodiversity and ecosystem services. Influential actors such as corporations, governments, and multilateral organizations have made commitments to meeting future agricultural demand sustainably and preserving critical ecosystems. Current approaches to predicting the impacts of agricultural expansion involve calculation of total land conversion and assessment of the impacts on biodiversity or ecosystem services on a per-area basis, generally assuming a linear relationship between impact and land area. However, the impacts of continuing land development are often not linear and can vary considerably with spatial configuration. We demonstrate what could be gained by spatially explicit analysis of agricultural expansion at a large scale compared with the simple measure of total area converted, with a focus on the impacts on biodiversity and carbon storage. Using simple modeling approaches for two regions of Brazil, we find that for the same amount of land conversion, the declines in biodiversity and carbon storage can vary two- to fourfold depending on the spatial pattern of conversion. Impacts increase most rapidly in the earliest stages of agricultural expansion and are more pronounced in scenarios where conversion occurs in forest interiors compared with expansion into forests from their edges. This study reveals the importance of spatially explicit information in the assessment of land-use change impacts and for future land management and conservation.

scholarly journals Environmental heterogeneity affects the location of modelled communities along the niche–neutrality continuum

2014 ◽  
Vol 281 (1783) ◽  
pp. 20133249 ◽  
Author(s):  
Avi Bar-Massada ◽  
Rafi Kent ◽  
Yohay Carmel
Keyword(s):  
Environmental Heterogeneity ◽  
Spatial Configuration ◽  
Continuum Hypothesis ◽  
Past Research ◽  
Spatially Explicit ◽  
Species Dispersal ◽  
Complex Interactions ◽  
Dispersal Characteristics ◽  
The Continuum

The continuum hypothesis has been proposed as a means to reconcile the contradiction between the niche and neutral theories. While past research has shown that species richness affects the location of communities along the niche–neutrality continuum, there may be extrinsic forces at play as well. We used a spatially explicit continuum model to quantify the effects of environmental heterogeneity, comprising abundance distribution and spatial configuration of resources, on the degree of community neutrality. We found that both components of heterogeneity affect the degree of community neutrality and that species' dispersal characteristics affect the neutrality–heterogeneity relationship. Narrower resource abundance distributions decrease neutrality, while spatial configuration, which is manifested by spatial aggregation of resources, decreases neutrality at higher aggregation levels. In general, the degree of community neutrality was affected by complex interactions among spatial configuration of resources, their abundance distributions and the dispersal characteristics of species in the community. Our results highlight the important yet overlooked role of the environment in dictating the location of communities along the hypothesized niche–neutrality continuum.

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