Past Guest Seminars
Speaker: Prof. Ulf Dieckmann (International Institute for Applied Systems Analysis (IIASA))
Date: Mar. 13th, 2019
Time: 13:00 -
Venue: Room 310, ESB building, Hayama Campus, SOKENDAI (総研大葉山キャンパス 先導科学研究科棟)
Title: Complex Adaptive Systems at the Interface of Ecology and Evolution, Statistical Physics, and Social Dynamics
Abstract:
Analyzing humankind’s interactions with our collective environment requires understanding complex adaptive systems. This is especially important for mitigating anthropogenic impacts on the biosphere, managing the multifaceted services provided by ecosystems, and shaping social structures and their dynamics. Complex adaptive systems share key features qualitatively setting them apart from simpler systems: they typically comprise large numbers of nonlinearly interacting agents; have a high propensity for collective dynamics, self-organization, and emergent phenomena; may involve complex behavior and rapid adaptation; incorporate aspects of their own history, causing path-dependence; and exhibit resilience punctuated by discontinuous change, implying tipping points and regime shifts. In this presentation, I will emphasize the interdisciplinary remit of research on complex adaptive systems by highlighting perspectives associated with ecology and evolution, statistical physics, and social dynamics. In regard to ecology and evolution, I will outline our work on food-web dynamics, fisheries-induced evolution, and biodiversity formation. In regard to statistical physics, I will mention research on moment approximations, critical exponents in evolutionary slowing down, and species packing. In regard to social dynamics, I will describe our efforts to understand the evolution of behavioral reaction norms, the optimal use of positive and negative incentives, and the dynamics of institutional corruption.
Speaker: Prof. Kalle Parvinen (University of Turku)
Date: Feb. 21st, 2019
Time: 13:00 -
Venue: Room 310, ESB building, Hayama Campus, SOKENDAI (総研大葉山キャンパス 先導科学研究科棟) Access
Title: Environmental dimensionality and singular values
Abstract:
According to the competitive exclusion principle, the number of regulating variables n in a given system is an upper bound on the number of coexisting species at equilibrium. However, on occasion it is possible to reformulate a model with a lower number of regulating variables than appeared in the initial specification. The smallest number of such variables is called the dimension of the environmental feedback, or environmental dimension for short.
For the study of equilibria (and many other attractors) it is enough to know the sign of each population growth rate, and therefore different indicators of population growth, so-called fitness proxies such as the basic reproduction number, are sometimes preferred. Unfortunately, different fitness proxies can engender different dimensions. Fundamental concepts like the dimension of the environmental feedback should not depend of such arbitrary choices. We resolve this by showing that the local dimension in points where fitness is zero is independent of the choice of a proxy, and thus a proper basis for a definition. The maximum of these local dimensions is called the effective dimension of the environmental feedback.
In parallel we investigate how the environmental dimension can be determined by analysing the two components of the environmental feedback: The impact map describes how the resident species affect the regulating variables, and the sensitivity map describes how population growth depends on the regulating variables. The impact dimension is lower than n when the feasible set of environments is of lower dimension than n, and sensitivity dimension is lower than n when not all environmental variables affect the sign of population growth independently. Their combined effect can result in an even lower environmental dimension. We illustrate such situations with examples. In view of these considerations we claim that the dimension of environmental feedback is the ultimate generalization of the concept "number of limiting, or regulating, factors", and thus the sharpest generally applicable upper bound on the number of species that can robustly coexist for communities built from an a priori delimited set of "species". Finally, a specific system may numerically be very close to a system with much smaller dimension, so that in practice a considerably smaller number of species may coexist. Therefore, the dimension as such does not necessarily provide a good estimate for the number of coexisting species. We thus investigate different measures of population regulation strength, and demonstrate the usefulness of singular values in determining the potential of species coexistence.
Joint work with Ulf Dieckmann and Hans Metz.
Speaker: Prof. Sergey Gavrilets (University of Tennessee)
Date: Feb. 1st, 2019
Time: 15:00 -
Venue: Room 310, ESB building, Hayama Campus, SOKENDAI (総研大葉山キャンパス 先導科学研究科棟 310セミナー室) Access
Title: Modeling the evolutionary origins and dynamics of social complexity
Abstract: It is now well recognized that understanding modern human behavior, psychology, culture, and certain economic and political processes is hardly possible without also considering factors and processes that were shaping our recent evolution. Deciphering the problems of human origins and subsequent social and cultural evolution requires a concerted effort of researchers from a diverse set of disciplines including biology, anthropology, psychology, economics, history as well as mathematics and computational science. If we, as scientists, are successful in this endeavor, the societal impact will be enormous. I will illustrate some of my recent modeling work in this area. I will consider the collective action problem in heterogeneous groups, effects of identify fusion on self-sacrifice, the evolution of social norm internalization, and the joint dynamics of power inequality and cooperation.
Speakers: Prof. Mike Boots, Prof. Sébastien Lion
Date: Jan. 18th, 2019
Time: 13:00 -
Venue: Room 310, ESB building, Hayama Campus, SOKENDAI (総研大葉山キャンパス 先導科学研究科棟 310セミナー室) Access
Mike Boots (University of California, Berkley)
Title : The central role of population structure in host pathogen interactions
Abstract:
Different forms of population structure are found across natural and managed systems and can have profound implications to infectious disease epidemiology and evolution. I will illustrate this by presenting modes that show how social structure in a natural mammal population can trap disease how metapopulation structure impacts patterns of resistance in a plant fungal system and how we can use spatial structure to help control vector populations. I will also illustrate a case where structure, in this case intensification in apiculture does not impact disease spread.
Sébastien Lion (Centre d'Écologie Fonctionnelle et Évolutive (CEFE) in Montpellier)
Title :
Evolution in structured populations
Abstract :
All natural populations are structured to some extent. In this talk, I will discuss the impact of spatial structure and class structure on evolution. First, I will present some theoretical insights on the evolution of parasite virulence in spatially structured host populations at both short- and long-term scales. Second, I will discuss how intrinsic differences between different classes of individuals can be taken into account using the concept of reproductive value. In particular, I will present a dynamical generalisation of reproductive value that sheds light on the interplay between demography and selection.