1,815 research outputs found
CHRYSANTHEMUM PRODUCTION PLANNING UNDER TIME-TO-HARVEST UNCERTAINTY
Crop Production/Industries,
Trophicâ specific responses to migration in empirical metacommunities
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154529/1/oik12963.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154529/2/oik12963_am.pd
Evolution of cooperation in multilevel public goods games with community structures
In a community-structured population, public goods games (PGG) occur both
within and between communities. Such type of PGG is referred as multilevel
public goods games (MPGG). We propose a minimalist evolutionary model of the
MPGG and analytically study the evolution of cooperation. We demonstrate that
in the case of sufficiently large community size and community number, if the
imitation strength within community is weak, i.e., an individual imitates
another one in the same community almost randomly, cooperation as well as
punishment are more abundant than defection in the long run; if the imitation
strength between communities is strong, i.e., the more successful strategy in
two individuals from distinct communities is always imitated, cooperation and
punishment are also more abundant. However, when both of the two imitation
intensities are strong, defection becomes the most abundant strategy in the
population. Our model provides insight into the investigation of the
large-scale cooperation in public social dilemma among contemporary
communities.Comment: 6 pages, 4 figures, Accepted by EP
Models for regional heartwater epidemiology in a variable environment
A model of the epidemic dynamics of heartwater within a cattle production unit was presented by
Yonow et al. (1998). Here, the model is expanded to a region consisting of several farms to study the
effect of environmental variability on control strategies. We have shown that:
• In a region, where the environment of each farm is modelled with constant epidemiologic parameter
values, while the between-farm parameter values differ, regional variation in the removal rate
of infected cattle increases the average fraction of infected cattle across the region , while regional
variation in the transmission rate of infection from ticks to cattle decreases the average fraction of
infected cattle, thereby requiring control measures that keep the removal rate uniform and the
transmission rate variable.
• In a region, where in addition to regional variation between farms, the epidemiologic parameters
of each farm are time-variant, then temporal variation in both the transmission rate and removal
rate increases the average fraction of infected cattle across the region, thereby requiring control
measures that keep both parameters uniform.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201
Probability and Social Science. Methodological Relationships between the Two Approaches
No abstract available
Forming agricultural bargaining units for a sustainable and equitable agriculture
This study examines the structure, function, and perceived success of an organic growers\u27 cooperative organization called OFARM
Minimizing the population extinction risk by migration
Many populations in nature are fragmented: they consist of local populations
occupying separate patches. A local population is prone to extinction due to
the shot noise of birth and death processes. A migrating population from
another patch can dramatically delay the extinction. What is the optimal
migration rate that minimizes the extinction risk of the whole population? Here
we answer this question for a connected network of model habitat patches with
different carrying capacities.Comment: 7 pages, 3 figures, accepted for publication in PRL, appendix
contains supplementary materia
Replicators in Fine-grained Environment: Adaptation and Polymorphism
Selection in a time-periodic environment is modeled via the two-player
replicator dynamics. For sufficiently fast environmental changes, this is
reduced to a multi-player replicator dynamics in a constant environment. The
two-player terms correspond to the time-averaged payoffs, while the three and
four-player terms arise from the adaptation of the morphs to their varying
environment. Such multi-player (adaptive) terms can induce a stable
polymorphism. The establishment of the polymorphism in partnership games
[genetic selection] is accompanied by decreasing mean fitness of the
population.Comment: 4 pages, 2 figure
The evolution of dispersal in a Levins’ type metapopulation model
We study the evolution of the dispersal rate in a metapopulation model with extinction and
colonisation dynamics, akin to the model as originally described by Levins. To do so we extend the metapopulation model with a description of the within patch dynamics. By means of a separation of time scales we analytically derive a fitness expression from first principles for this model. The fitness function can be written as an inclusive fitness equation (Hamilton’s rule). By recasting this equation in a form that emphasizes the effects of competition we show the effect of the local competition and on the local population size on the evolution of dispersal. We find that the evolution of dispersal cannot be easily interpreted in terms of avoidance of kin competition, but rather that increased dispersal reduces the competitive ability. Our model also yields a testable
prediction in term of relatedness and life history parameters
Fast migration and emergent population dynamics
We consider population dynamics on a network of patches, each of which has a
the same local dynamics, with different population scales (carrying
capacities). It is reasonable to assume that if the patches are coupled by very
fast migration the whole system will look like an individual patch with a large
effective carrying capacity. This is called a "well-mixed" system. We show
that, in general, it is not true that the well-mixed system has the same
dynamics as each local patch. Different global dynamics can emerge from
coupling, and usually must be figured out for each individual case. We give a
general condition which must be satisfied for well-mixed systems to have the
same dynamics as the constituent patches.Comment: 4 page
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