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