Bulletin of the American Physical Society
78th Annual Meeting of the Southeastern Section of the APS
Volume 56, Number 9
Wednesday–Saturday, October 19–22, 2011; Roanoke, Virginia
Session JD: Statistical Physics Far from Equilibrium |
Hide Abstracts |
Chair: Henry Greenside, Duke University Room: Crystal Ballroom DE |
Friday, October 21, 2011 1:30PM - 2:00PM |
JD.00001: The Emergence of Community Structure in Metacommunities Invited Speaker: The role of space in determining species coexistence and community structure is well established. However, previous studies mainly focus on simple competition and predation systems, and the role of mutualistic interspecies interactions is not well understood. Here we use a spatially explicit metacommunity model, in which new species enter by a mutation process, to study the effect of fitness-dependent dispersal on the structure of communities with interactions comprising mutualism, competition, and exploitation [1,2]. We find that the diversity and the structure of the interaction network undergo a nonequilibrium phase transition with increasing dispersal rate. {\em Low\/} dispersion rate favors spontaneous emergence of many dissimilar, strongly mutualistic and species- poor local communities. Due to the local dissimilarities, the global diversity is high. {\em High\/} dispersion rate promotes local biodiversity and supports similar, species-rich local communities with a wide range of interactions. The strong similarity between neighboring local communities leads to reduced global diversity.\\[4pt] [1] E.~Filotas, M.~Grant, L.~Parrott, P.A.\ Rikvold, J.\ Theor.\ Biol.\ {\bf 266}, 419 (2010).\\[0pt] [2] E.~Filotas, M.~Grant, L.~Parrott, P.A.\ Rikvold, Ecol.\ Modell.\ {\bf 221}, 885 (2010). [Preview Abstract] |
Friday, October 21, 2011 2:00PM - 2:30PM |
JD.00002: Cyclically competing species: deterministic trajectories and stochastic evolution Invited Speaker: Generalizing the cyclically competing three-species model (often referred to as the rock-paper-scissors game), we consider a simple system of population dynamics that involves four species. We discuss both well-mixed systems, i.e. without spatial structure, and spatial systems on one- and two-dimensional regular lattices. Unlike the three-species model, the four species form alliance pairs which resemble partnership in the game of Bridge. In a finite system with discrete stochastic dynamics, all but four of the absorbing states consist of coexistence of a partner-pair. For the system without spatial structure mean-field theory predicts complex time dependence of the system and that the surviving partner-pair is the one with the larger product of their strengths (rates of consumption). Beyond mean-field much richer behavior is revealed, including complicated extinction probabilities and non-trivial distributions of the population ratio in the surviving pair. For the lattice systems, we discuss the growth of domains and the related extinction events, thereby confronting our results with those obtained for the three-species case. [Preview Abstract] |
Friday, October 21, 2011 2:30PM - 3:00PM |
JD.00003: Stochastic population oscillations in spatial predator-prey models Invited Speaker: It is well-established that including spatial structure and stochastic noise in models for predator-prey interactions invalidates the classical deterministic Lotka-Volterra picture of neutral population cycles. In contrast, stochastic models yield long-lived, but ultimately decaying erratic population oscillations, which can be understood through a resonant amplification mechanism for density fluctuations. In Monte Carlo simulations of spatial stochastic predator-prey systems, one observes striking complex spatio-temporal structures. These spreading activity fronts induce persistent correlations between predators and prey. In the presence of local particle density restrictions (finite prey carrying capacity), there exists an extinction threshold for the predator population. The accompanying continuous non-equilibrium phase transition is governed by the directed-percolation universality class. We employ field-theoretic methods based on the Doi-Peliti representation of the master equation for stochastic particle interaction models to (i) map the ensuing action in the vicinity of the absorbing state phase transition to Reggeon field theory, and (ii) to quantitatively address fluctuation-induced renormalizations of the population oscillation frequency, damping, and diffusion coefficients in the species coexistence phase. [See Preprint arXiv:1105.4242, and further refs. therein.] [Preview Abstract] |
Friday, October 21, 2011 3:00PM - 3:30PM |
JD.00004: Accumulation of beneficial mutations in low dimensions Invited Speaker: When beneficial mutations are relatively common, competition between multiple unfixed mutations can reduce the rate of fixation in well-mixed asexual populations. We introduce a one-dimensional model with a steady accumulation of beneficial mutations. We find a transition between periodic selection and multiple-mutation regimes. In the multiple-mutation regime, the increase of fitness along the lattice bears is similar to surface growth phenomena, with power-law growth, saturation of the interface width, and KPZ universality class exponents. We also find significant differences compared to the well-mixed model. In our lattice model, the transition between regimes happens at a much lower mutation rate due to slower fixation times in one dimension. Also, the rate of fixation is reduced with increasing mutation rate due to the more intense competition, and it saturates with large population size. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700