Is there chaos out there? : analysis of complex dynamics in plankton communities

Species often show irregular fluctuations in their population abundances. Traditionally, ecologists have thought that external processes (e.g., variability in weather conditions) are the main drivers of these ups and downs. However, recent theoretical work suggests that fluctuations in natural populations may also be driven by internal mechanisms (e.g., the interplay between species). In this thesis I use a combination of time series analysis and modeling to provide more insight into the question to which extent such internally generated chaos might drive the population dynamics of plankton communities under controlled as well as natural conditions. In short, this thesis demonstrates in theory and experiment that species in plankton communities may rise and fall forever in a chaotic way. This result challenges the traditional view that nature is at equilibrium and that only externally driven processes may disturb this equilibrium

Subjects, Topics, and Anchoring to the Context

The article discusses the connection between the syntactic and semantic properties of weak, strong, and referential DP subjects. In particular, I argue that nominal expressions possess a situation argument and that their interpretation and their distribution follow from the presuppositional requirements that the determiner imposes on the individual argument and situation argument of its complement nominal. These presuppositional requirements, I then argue, are embodied by local relations of the subject to a distinct head in the C domain, Fin(0) in the system of Rizzi 1997, where specific referential values of discourse antecedents are accessible

Visualizing the Template of a Chaotic Attractor

Chaotic attractors are solutions of deterministic processes, of which the topology can be described by templates. We consider templates of chaotic attractors bounded by a genus-1 torus described by a linking matrix. This article introduces a novel and unique tool to validate a linking matrix, to optimize the compactness of the corresponding template and to draw this template. The article provides a detailed description of the different validation steps and the extraction of an order of crossings from the linking matrix leading to a template of minimal height. Finally, the drawing process of the template corresponding to the matrix is saved in a Scalable Vector Graphics (SVG) file.Comment: Appears in the Proceedings of the 26th International Symposium on Graph Drawing and Network Visualization (GD 2018

Long-term cyclic persistence in an experimental predator–prey system

Predator–prey cycles rank among the most fundamental concepts in ecology, are predicted by the simplest ecological models and enable, theoretically, the indefinite persistence of predator and prey1,2,3,4. However, it remains an open question for how long cyclic dynamics can be self-sustained in real communities. Field observations have been restricted to a few cycle periods5,6,7,8 and experimental studies indicate that oscillations may be short-lived without external stabilizing factors9,10,11,12,13,14,15,16,17,18,19. Here we performed microcosm experiments with a planktonic predator–prey system and repeatedly observed oscillatory time series of unprecedented length that persisted for up to around 50 cycles or approximately 300 predator generations. The dominant type of dynamics was characterized by regular, coherent oscillations with a nearly constant predator–prey phase difference. Despite constant experimental conditions, we also observed shorter episodes of irregular, non-coherent oscillations without any significant phase relationship. However, the predator–prey system showed a strong tendency to return to the dominant dynamical regime with a defined phase relationship. A mathematical model suggests that stochasticity is probably responsible for the reversible shift from coherent to non-coherent oscillations, a notion that was supported by experiments with external forcing by pulsed nutrient supply. Our findings empirically demonstrate the potential for infinite persistence of predator and prey populations in a cyclic dynamic regime that shows resilience in the presence of stochastic events

Infinitive Wh-relatives in romance : consequences for the truncation-versus-intervention debate

Romance clitic left dislocation is widespread across all kinds of nonroot contexts, but it is forbidden in infinitive wh-relatives. This article investigates the extent and nature of this restriction and the consequences it raises for the truncation and intervention analyses of the left periphery of embedded sentences. We will show that current proposals cannot account for the whole gamut of data. In consequence, we will propose that infinitive wh-relatives display a maximally syncretic left periphery, whereas infinitive wh-interrogatives have a full-fledged left periphery, crucially involving ForceP, because they are selected by a higher predicate. This crucial difference between infinitive relatives and interrogatives will also be shown to be consistent with the existence of specialized complementizers for the former but not the latte

Discourse, sentence grammar and the left periphery of the clause

The term left periphery refers to that area on the left of the subject, in the syntactic representation of a clause, where the relationships with the context are encoded. In this work I propose a syntactic analysis that goes beyond mere sentence grammar and integrates prosodic and discourse features as well. On the one hand, this move accounts for some observations previously not fully understood, such as the anomalous syntactic properties of Clitic Left Dislocation and Hanging Topic, their differences with respect to Focus and their similarities with parentheticals. On the other, it aims at providing a theory of grammar able to encode the relationships between sentence grammar, context and bigger units such as discourses

Is there chaos out there? : analysis of complex dynamics in plankton communities

Species often show irregular fluctuations in their population abundances. Traditionally, ecologists have thought that external processes (e.g., variability in weather conditions) are the main drivers of these ups and downs. However, recent theoretical work suggests that fluctuations in natural populations may also be driven by internal mechanisms (e.g., the interplay between species). In this thesis I use a combination of time series analysis and modeling to provide more insight into the question to which extent such internally generated chaos might drive the population dynamics of plankton communities under controlled as well as natural conditions. In short, this thesis demonstrates in theory and experiment that species in plankton communities may rise and fall forever in a chaotic way. This result challenges the traditional view that nature is at equilibrium and that only externally driven processes may disturb this equilibrium