7,698 research outputs found
Evolutionary comparison between viral lysis rate and latent period
Marine viruses shape the structure of the microbial community. They are,
thus, a key determinant of the most important biogeochemical cycles in the
planet. Therefore, a correct description of the ecological and evolutionary
behavior of these viruses is essential to make reliable predictions about their
role in marine ecosystems. The infection cycle, for example, is indistinctly
modeled in two very different ways. In one representation, the process is
described including explicitly a fixed delay between infection and offspring
release. In the other, the offspring are released at exponentially distributed
times according to a fixed release rate. By considering obvious quantitative
differences pointed out in the past, the latter description is widely used as a
simplification of the former. However, it is still unclear how the dichotomy
"delay versus rate description" affects long-term predictions of host-virus
interaction models. Here, we study the ecological and evolutionary implications
of using one or the other approaches, applied to marine microbes. To this end,
we use mathematical and eco-evolutionary computational analysis. We show that
the rate model exhibits improved competitive abilities from both ecological and
evolutionary perspectives in steady environments. However, rate-based
descriptions can fail to describe properly long-term microbe-virus
interactions. Moreover, additional information about trade-offs between
life-history traits is needed in order to choose the most reliable
representation for oceanic bacteriophage dynamics. This result affects deeply
most of the marine ecosystem models that include viruses, especially when used
to answer evolutionary questions.Comment: to appear in J. Theor. Bio
The Survival of the Conformist: Social Pressure and Renewable Resource Management
This paper examines the role of pro-social behavior as a mechanism for the establishment and maintenance of cooperation in resource use under variable social and environmental conditions. By coupling resource stock dynamics with social dynamics concerning compliance to a social norm prescribing non-excessive resource extraction in a common pool resource (CPR), we show that when reputational considerations matter and a sufficient level of social stigma affects the violators of a norm, sustainable outcomes are achieved. We find large parameter regions where norm-observing and norm-violating types coexist, and analyze to what extent such coexistence depends on the environment.Cooperation, Social Norm, Ostracism, Common Pool Resource, Evolutionary Game Theory, Replicator Equation, Agent-based Simulation, Coupled Socio-resource Dynamics
Evolution at the ecosystem level: On the evolution of ecosystem patterns
A mesura que problemes ambientals com la superpoblació,
la sobrepesca, la contaminació i la pluja àcida han
rebut més atenció pública, l'interès s'ha centrat més en vincles
biogeoquímics i en estudis integrals d'ecosistemes sencers.
Ramon Margalef va reconèixer fermament la notable influència
intel·lectual que es podria obtenir mitjançant la transferència,
d'un camp a un altre, de les perspectives i avenços de cadascun
d'ells. En aquest article voldria tractar la naixent unificació
de la biologia de poblacions i la ciència dels ecosistemes. La
gestió sostenible requereix que es relacionin les característiques
macroscòpiques de les comunitats i els ecosistemes
amb els detalls microscòpics dels individus i les poblacions.
Sostindré que les diferències que han impedit aquesta síntesi
són artificials i que les hem de superar per a poder construir
una ciència que ens permeti afrontar la pèrdua dels beneficis
que es deriven dels ecosistemes.As environmental problems like overpopulation,
overfishing, pollution and acid rain commanded greater public
attention, much focus shifted to biogeochemical linkages, and
to holistic studies of whole ecosystems. Ramon Margalef recognized
as forcefully as anyone the remarkable intellectual leverage
one could gain by transferring the unique perspectives
and advances from one field to another. In this article I discuss
the nascent unification of population biology and ecosystems
science. Sustainable management requires that we relate the
macroscopic features of communities and ecosystems to the
microscopic details of individuals and populations. I argue that
the distinctions that have prevented this synthesis are artificial,
and that we need to overcome them to build a science that allows
us to deal with the loss of the benefits we derive from ecosystems
Fundamental Questions in Biology
The pace of our understanding of biology has engendered increasing specialization but there are still common fundamental challenges that unify biology and should form the core of future research
Cosmological Moduli Dynamics
Low energy effective actions arising from string theory typically contain
many scalar fields, some with a very complicated potential and others with no
potential at all. The evolution of these scalars is of great interest. Their
late time values have a direct impact on low energy observables, while their
early universe dynamics can potentially source inflation or adversely affect
big bang nucleosynthesis. Recently, classical and quantum methods for fixing
the values of these scalars have been introduced. The purpose of this work is
to explore moduli dynamics in light of these stabilization mechanisms. In
particular, we explore a truncated low energy effective action that models the
neighborhood of special points (or more generally loci) in moduli space, such
as conifold points, where extra massless degrees of freedom arise. We find that
the dynamics has a surprisingly rich structure - including the appearance of
chaos - and we find a viable mechanism for trapping some of the moduli.Comment: 35 pages, 14 figures, references adde
Equation-free modeling of evolving diseases: Coarse-grained computations with individual-based models
We demonstrate how direct simulation of stochastic, individual-based models
can be combined with continuum numerical analysis techniques to study the
dynamics of evolving diseases. % Sidestepping the necessity of obtaining
explicit population-level models, the approach analyzes the (unavailable in
closed form) `coarse' macroscopic equations, estimating the necessary
quantities through appropriately initialized, short `bursts' of
individual-based dynamic simulation. % We illustrate this approach by analyzing
a stochastic and discrete model for the evolution of disease agents caused by
point mutations within individual hosts. % Building up from classical SIR and
SIRS models, our example uses a one-dimensional lattice for variant space, and
assumes a finite number of individuals. % Macroscopic computational tasks
enabled through this approach include stationary state computation, coarse
projective integration, parametric continuation and stability analysis.Comment: 16 pages, 8 figure
Cities, The Sharing Economy and What's Next
This report seeks to provide an analysis of what is currently happening in American cities so that city leaders may better understand, encourage and regulate the growing sharing economy. Interviews were conducted with city officials on the impact of the sharing economy and related topics, and the report centers around five key themes: innovation, economic development, equity, safety and implementation.The sharing economy is also commonly referred to as collaborative consumption, the collaborative economy, or the peer-to-peer economy. This term refers to business models that enable providers and consumers to share resources and services, from housing to vehicles and more. These business models typically take the form of an online and/or application-based platform for business transactions
- …