TY - GEN A1 - Ehrlich, Elias A1 - Gaedke, Ursula T1 - Not attackable or not crackable BT - How pre-and post-attack defenses with different competition costs affect prey coexistence and population dynamics T2 - Ecology and Evolution N2 - It is well-known that prey species often face trade-offs between defense against predation and competitiveness, enabling predator-mediated coexistence. However, we lack an understanding of how the large variety of different defense traits with different competition costs affects coexistence and population dynamics. Our study focusses on two general defense mechanisms, that is, pre-attack (e.g., camouflage) and post-attack defenses (e.g., weaponry) that act at different phases of the predator—prey interaction. We consider a food web model with one predator, two prey types and one resource. One prey type is undefended, while the other one is pre-or post-attack defended paying costs either by a higher half-saturation constant for resource uptake or a lower maximum growth rate. We show that post-attack defenses promote prey coexistence and stabilize the population dynamics more strongly than pre-attack defenses by interfering with the predator’s functional response: Because the predator spends time handling “noncrackable” prey, the undefended prey is indirectly facilitated. A high half-saturation constant as defense costs promotes coexistence more and stabilizes the dynamics less than a low maximum growth rate. The former imposes high costs at low resource concentrations but allows for temporally high growth rates at predator-induced resource peaks preventing the extinction of the defended prey. We evaluate the effects of the different defense mechanisms and costs on coexistence under different enrichment levels in order to vary the importance of bottom-up and top-down control of the prey community. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 466 KW - coexistence KW - competition–defense trade‐off KW - defense against predation KW - functional response KW - indirect facilitation KW - predator–prey cycles Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-417391 ER - TY - JOUR A1 - Gaedke, Ursula A1 - Meuresch, David A1 - Plate, Simon A1 - Strauß, Katharina A1 - Frädrich, Henriette A1 - Schwarz, Franziska A1 - Gebbert, Daniela A1 - Dudenhause, Joachim T1 - Portal alumni T2 - Das Ehemaligen-Magazin der Universität Potsdam N2 - Offenheit, Vertrauen und Zuverlässigkeit – das sind wichtige Säulen langanhaltender und erfolgreicher Partnerschaften. Partnerschaften auf Augenhöhe, die auf Freiwilligkeit, gegenseitigem Wohlwollen, Respekt, Vertrauen und Wertschätzung beruhen, werden auch an der Universität Potsdam gebraucht und gefördert. Sie entstehen zwischen Lehrenden, Studierenden und Alumni oder sie werden gelebt in vielfältigen Kontakten der Universität mit Stakeholdern in Politik, Wirtschaft und Gesellschaft. Wie in jeder Partnerschaft gilt auch hier das Prinzip des gegenseitigen Gebens und Nehmens. Sind Ziele, Rollen, Erwartungen und Rahmenbedingungen geklärt, kann aus einem ersten Gespräch eine neue Perspektive, ein zündender Impuls, eine Entscheidungshilfe oder sogar eine langjährige Kooperation werden. In dem 15. Heft unseres Alumni-Magazins berichten wir von solchen Partnerschaften. So stellen wir Biologieprofessorin Ursula Gaedke vor, die zu ihren ehemaligen Studierenden und Mitarbeitern langjährige Kontakte pflegt, von denen beide Seiten profitieren. Wir berichten aber auch vom Partnerkreis „Industrie & Wirtschaft“, der Unternehmen und die Universität Potsdam verbindet. Mit diesem Netzwerk wird die Fachkräftesicherung in der Region unterstützt und der Wissenstransfer gefördert. Die Vermittlung von Studierenden und Absolventen ist dabei ein wichtiger Baustein. Und nicht zuletzt kommen Ehemalige der Universität zu Wort und erzählen von ihren Partnerschaften zu Studierenden. Katharina Strauß beispielsweise, gibt ihre Erfahrungen aus dem Jurastudium und dem Berufsleben seit zehn Jahren an Studentinnen ihres Faches weiter. Im Juristinnen-Mentoring-Programm gibt sie Anstöße und neue Impulse und mildert so manche Prüfungsangst. Darüber hinaus stellen wir in diesem Heft auch wieder aktuelle Projekte Ihrer Alma Mater vor und berichten von den Höhepunkten des Jahres 2018. T3 - Portal alumni : das Ehemaligen-Magazin der Universität Potsdam - 15/2018 Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-445460 EP - 15 ER - TY - GEN A1 - Raatz, Michael A1 - van Velzen, Ellen A1 - Gaedke, Ursula T1 - Co‐adaptation impacts the robustness of predator–prey dynamics against perturbations T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Global change threatens the maintenance of ecosystem functions that are shaped by the persistence and dynamics of populations. It has been shown that the persistence of species increases if they possess larger trait adaptability. Here, we investigate whether trait adaptability also affects the robustness of population dynamics of interacting species and thereby shapes the reliability of ecosystem functions that are driven by these dynamics. We model co‐adaptation in a predator–prey system as changes to predator offense and prey defense due to evolution or phenotypic plasticity. We investigate how trait adaptation affects the robustness of population dynamics against press perturbations to environmental parameters and against pulse perturbations targeting species abundances and their trait values. Robustness of population dynamics is characterized by resilience, elasticity, and resistance. In addition to employing established measures for resilience and elasticity against pulse perturbations (extinction probability and return time), we propose the warping distance as a new measure for resistance against press perturbations, which compares the shapes and amplitudes of pre‐ and post‐perturbation population dynamics. As expected, we find that the robustness of population dynamics depends on the speed of adaptation, but in nontrivial ways. Elasticity increases with speed of adaptation as the system returns more rapidly to the pre‐perturbation state. Resilience, in turn, is enhanced by intermediate speeds of adaptation, as here trait adaptation dampens biomass oscillations. The resistance of population dynamics strongly depends on the target of the press perturbation, preventing a simple relationship with the adaptation speed. In general, we find that low robustness often coincides with high amplitudes of population dynamics. Hence, amplitudes may indicate the robustness against perturbations also in other natural systems with similar dynamics. Our findings show that besides counteracting extinctions, trait adaptation indeed strongly affects the robustness of population dynamics against press and pulse perturbations. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 809 KW - disturbance KW - evolutionary rescue KW - population dynamics KW - stability KW - trait adaptation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-442489 SN - 1866-8372 IS - 809 ER - TY - GEN A1 - van Velzen, Ellen A1 - Gaedke, Ursula T1 - Reversed predator BT - prey cycles are driven by the amplitude of prey oscillations N2 - Ecoevolutionary feedbacks in predator–prey systems have been shown to qualitatively alter predator–prey dynamics. As a striking example, defense–offense coevolution can reverse predator–prey cycles, so predator peaks precede prey peaks rather than vice versa. However, this has only rarely been shown in either model studies or empirical systems. Here, we investigate whether this rarity is a fundamental feature of reversed cycles by exploring under which conditions they should be found. For this, we first identify potential conditions and parameter ranges most likely to result in reversed cycles by developing a new measure, the effective prey biomass, which combines prey biomass with prey and predator traits, and represents the prey biomass as perceived by the predator. We show that predator dynamics always follow the dynamics of the effective prey biomass with a classic ¼‐phase lag. From this key insight, it follows that in reversed cycles (i.e., ¾‐lag), the dynamics of the actual and the effective prey biomass must be in antiphase with each other, that is, the effective prey biomass must be highest when actual prey biomass is lowest, and vice versa. Based on this, we predict that reversed cycles should be found mainly when oscillations in actual prey biomass are small and thus have limited impact on the dynamics of the effective prey biomass, which are mainly driven by trait changes. We then confirm this prediction using numerical simulations of a coevolutionary predator–prey system, varying the amplitude of the oscillations in prey biomass: Reversed cycles are consistently associated with regions of parameter space leading to small‐amplitude prey oscillations, offering a specific and highly testable prediction for conditions under which reversed cycles should occur in natural systems. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 433 KW - coevolution KW - ecoevolutionary dynamics KW - predator-prey dynamics KW - top-down control Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-411652 ER -