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This is the joint group meeting of the research groups in Applied Systems Science and Theoretical Systems Science. We discuss new results, bounce off new ideas, practice talks, and do journals clubs - just to mention a few of our activities.

We are always happy to host guests and visitors. If you're interested or would like get involved, please don't hesitate to get in touch!

Summer Semester 2015

Timetable

Date Time Presenter  Title Room Note
Tue 05.05.2015 10:15 Prof. Dr. Horst Malchow
Institute of Environmental Systems Research, Osnabrück
Ingredients of spatiotemporal pattern formation in population dynamics. 35/E25 USF Research Seminar
Wed 06.05.2015 11:00 Prof. Dr. Frank M. Hilker
Institute of Environmental Systems Research, Osnabrück
Introduction to XPPAUT. 66/E16
Tue 12.05.2015 10:15 Prof. Dr. Eduardo Liz
University of Vigo (Spain)
Logistic population models revisited. 35/E25 USF Research Seminar
Tue 02.06.2015 10:15 Vanessa Schakau
Institute of Environmental Systems Research, Osnabrück
Infectious diseases in streams and rivers. 35/E25 USF Research Seminar
Fri 05.06.2015 11:00 Daniel Ritterskamp
University of Oldenburg
Evolutionary Dynamics in Food Webs: Influence of Interaction Range, Resource Distribution and Space 66/E01
Mon 08.06.2015 16:00 Fanny Groll
University of Cologne
Chaotic attractor in 2-prey-1-predator-system originates from interplay of limit cycles 66/E01
Tue 09.06.2015 10:15 Virgile Baudrot
Université de Franche-Comté, Besançon (FRA)
The foraging behavior on trophically transmitted parasites. 35/E25
Tue 16.06.2015 10:15 Federico Roccati
University of Torino (ITA)
Packs of predators vs. groups of prey 35/E25
Marta Paliaga
University of Torino (ITA)
Disease infection undermining predator cooperation 35/E25
Thu 18.06.2015 11:30 Zepeng Sun
University of Amsterdam (The Netherlands)
What can we learn from seasonal reproduction? 93/E15
Fri 19.06.2015 11:30 Gunnar Petter
University of Göttingen
Simulating the long-term dynamics of tropical forests using functional-structural tree models 35/E23-E24
Mon 22.06.2015 11:30 Veronika Bernhauerova
Masaryk University, Brno (Czech Republic)
Evolution of male-killing in horizontally transmitted parasites 66/101
Tue 23.06.2015 10:15 Philipp Gorris
Institute of Environmental Systems Research, Osnabrück
Developing a Graduate School at the IUSF - Introduction and Discussion 35/E25 USF Research Seminar
Thu 25.06.2015 11:30 Matthew W. Adamson
University of Leicester (UK)
Cyclic competition, virus evolution and structural sensitivity 35/E21
Fri 26.06.2015 11:00 Michael Bengfort
Institute of Environmental Systems Research, Osnabrück
Some ideas of the Dynatrait project and possible contributions. 66/E01
Tue 14.07.2015 11:15 Alexander Ahring
Institute of Environmental Systems Research, Osnabrück
Modellansatz zur Berücksichtigung diffuser Substanzeinträge in Fließgewässer für das georeferenzierte Expositionsmodell GREAT-ER. (Master Thesis) 35/E25
Thu 30.07.2015 15:00 Eric Siero
Leiden University (NL)
Resilience of banded vegetation on slopes. 66/E01
Tue 11.08.2015 14:00 Jane Ndungu
University of Twente (NL)
Synergy in system modeling, field measurements, and remote sensing 93/E01
Thu 20.08.2015 13:30 Practice talks MPDE-15 t.b.a.

Abstracts of selected talks

Eduardo Liz, Departamento de Matemática Aplicada II, Universidad de Vigo (España)

Logistic population models revisited

The logistic equation is one of the best known models of population growth. The original ODE proposed by Verhulst inspired other related models which exhibit rich dynamics; for example, the discrete logistic equation (quadratic map) became a paradigm of chaos after the seminal papers of May.

In this talk, we consider logistic models of exploited populations, focusing on the changes in the dynamics as the harvesting effort is increased. In this way, we discuss the global dynamics and highlight the link among different logistic equations usually employed in population models.

Daniel Ritterskamp and Bernd Blasius (ICBM, University of Oldenburg)

Evolutionary Dynamics in Food Webs:  Influence of Interaction Range, Resource Distribution and Space

Food webs encode feeding interactions in ecological communities, originating from an interplay of evolutionary and ecological processes. Here we develop an evolutionary food web model in which feeding interactions between species are related to the relative distance of their adaptive traits in niche space. We present three model variants, which are analyzed using numerical simulations in combination with adaptive theory.

First, considering a single trait (bodysize), we uncover novel evolutionary dynamics, characterized by oscillations of bodysize within whole trophic guilds. Next, we study a system driven by two basal resources at different niche positions. For certain resource configurations this can lead to a dynamic instability of the food web, because the predators can not optimize their trait position towards both resources. This results into tight coupling of ecological and evolutionary dynamics, giving rise to biomass oscillations and intermittence in the population dynamic. Finally, we embed the model into a two dimensional niche space, where the additional niche axis might describe a spatial coordinate. The model is able to produce a wide range of static and dynamic food webs, depending on the width of the interaction kernel.

The structure of these food webs has common features with empirical data (e.g. intervality) that other models lack to describe. We conclude that the interaction of ecological and evolutionary dynamics can give rise to complex behaviour, such as sustained oscillations, intermittency, and ongoing evolution. Combined with spatial considerations, our studies have the potential to predict evolutionary behaviour in real food webs.

Fanny Groll

University of Cologne

Chaotic attractor in 2-prey-1-predator-system originates from interplay of limit cycles

We investigate the appearance of chaos in communities promoting coexistence. Our paradigm is an aquatic microbial food web comprising two prey and a predator species. We show that even in this small system a regime of chaotic population dynamics is formed over a wide range of intermediate dilution strengths. Specifically, the numerical simulation of the system reveals the presence of a chaotic attractor in the intermediate parameter window between two regimes of periodic coexistence (stable limit cycles). The intermediate structure provides the basis for the stable coexistence of all three species: environmental perturbations may result in huge fluctuations in species abundances, however, the system at large tolerates those perturbations in the sense that the population abundances quickly fall back onto the chaotic attractor manifold and the system remains. This mechanism explains how chaos helps the system to persist and stabilize against migration. The model is in agreement with laboratory studies.

Virgile Baudrot, Antoine Perasso, Clémentine Fritsch and Francis Raoul

Laboratoire Chrono-environnement – UMR 6249, Université de Franche-Comté / CNRS, 16 route de Gray, 25000 Besançon (France)

The foraging behavior on trophically transmitted parasites

Small mammal populations display fluctuating patterns of densities in many ecosystems worldwide, leading their predators to adapt their foraging strategy (the multi-species functional response, MSFR). The predator-preys relationship is the route of transmission of a large number of zoonotic parasites with a complex life cycle (infecting different hosts during their life), like the cestode Echinococcus multilocularis (Em). This parasite is widely distributed in the Northern Hemisphere and is the causative agent of the emerging zoonosis alveolar echinococcosis in humans. The red fox Vulpes vulpes is a typical definitive host (DH) of Em, with, in eastern France, the rodents Microtus arvalis and Arvicola scherman as intermediate hosts.

We described this eco-epidemiological system with ODEs and we computed the basic reproductive number R0, i.e., the number of secondary infections caused by a single primary infection into an otherwise susceptible population. We developed a general approach to model MSFR including accessibility to resources and switching of prey preference by predator. In this framework, we investigated the importance of MSFR and intermediate host diversity on the transmission patterns of Em. Few works have coupled adaptive predator-prey interactions with parasite transmissions, and the inclusion of switching behavior is a first attempt to feed hot topics linking adaptive foraging behavior and IHs diversity. We showed that switching of prey preference may have a dilution or amplification effect, that is a decrease, resp. increase, of the disease risk with an increase of IHs diversity.