Winter Graduate School 2013

The one-week workshop on “Ecological Theory” (3-9 February 2013) was organized by the PhD Program in Ecology, a joint initiative of the University of Zurich and ETH Zurich. The workshop was co-funded by the "SUK-Doktoratsprogramme" of Graduate Campus UZH and Centro Stefano Franscini ETH Zurich.

PhD students got the unique opportunity to interact directly with researchers who were instrumental in developing some of the theory behind ecology. The students practiced in developing research proposals and in discussing their ideas in groups.

Session abstracts

Introduction to Ecological Theory
A general theory of ecology consists of a description of ecology and a set of fundamental principles. This introductory session will discuss the development of and principles underpinning major ecological theories. The session will overarch the fundamental concepts of ecology that will be presented over the next five days. Among the topics covered will be the need for and methods of testing for ecological theory, and the interface between conceptual and experimental research.

Coexistence-Competition
Among the most enduring mysteries in ecology is how multiple plant species, all competing for the same handful of limiting resources, coexist. Classic theory shows that stable coexistence requires competitors to differ in their niches, and this finding has motivated countless investigations of ecological differences presumed to maintain diversity. That niche differences are key to coexistence, however, has recently been challenged by the neutral theory, which explains coexistence by the equivalence of competitors. The ensuing controversy has motivated calls for better understanding the collective importance of niche differences for the diversity observed in natural systems. In a series of presentations, we will first explore how the maintenance of species diversity can be understood in terms of niche and fitness differences between competitors, and how species trait and phylogenetic differences relate to these controls over the outcome of competition. We will next explore explanations for diversity maintenance focusing on the role of variation among individuals in their traits and vital rates. We will examine how variation among individuals reveals species level variation that is difficult to ascertain without exploring dynamics at the individual level. Empirical examples from forest environments will be presented to illustrate these points. We will next examine general rules for when and how individual variation per se influences the outcome of competition. At completion of the session, students will understand the leading approaches to exploring how species diversity is maintained.

Causes and Consequences of Extinctions
Each year between 0.1 and 0.01 % of the world’s species go extinct. That is, with about 1.8 million scientifically identified species, between 180 and 1.800 species vanishing year by year. But the actual losses are expected to be much higher since we don’t know exactly how many species there are. Moreover, the recent species loss is 1.000 times faster than the background or natural extinction rate. We crucially depend on a diverse planet. The loss of species will affect our wellbeing directly and indirectly. Thus, the search for the causes will help us to avoid extinctions; and by understanding the consequences arising from extinctions we will be able to disrupt potential cascade effects and mitigate the impacts of species loss.
However, identifying the causes and consequences of extinctions is one of the most challenging parts of ecological research. Species are part of a community and form complex networks of interactions. The ways species interact with each other are countless comprising competition, predation, parasitism, commensalism, mutualism and antagonism, just to mention a few. Thus, changes in the state of one species are likely to affect other species and therefore being carried forward throughout the community. The question are: How strong are other species affected? And how far are impacts carried forward. To answer these questions and to test for hypothesized mechanisms, ecologists conduct experiments and perform model simulations. This day of the workshop will give an overview on how to investigate extinctions and their impacts on communities and ecosystems. We will tell you about the possible interactions involved and when they are becoming important. Further, we will show you how to tackle the difficulties appearing when investigating complex interaction networks.

Host-Parasite Interactions
Host-Parasite interactions are a fundamental component of individual, population and community ecology. Parasites and pathogens are common and drive ecological and evolutionary responses in their host populations, which are reciprocated by the parasite and pathogen populations. Dynamics of host parasite interactions are modeled using different approaches. Some models base on population biology, while some base on ecological and evolutionary genetics. Mathematical models provide ample opportunities for testing the specific hypotheses of coevolution, disease dynamics and population level effects of pathogens. Purpose of this session is to give an overview of ecological and evolutionary models of coevolution. We aim at covering both infectious disease agents and classical parasites; their epidemiology, evolution of virulence and life-history traits. We specifically discuss how co-evolutionary models can be used to study ecological interactions, spatial and temporal heterogeneity and specificity. We give an overview, with examples, on how different models are tested and applied.

Metacommunity Theory / Ecological Networks
Understanding the distribution of species, their abundance, and their interactions with other species is the central theme of ecology. The study of how spatial dynamics explain the origin and maintenance of biodiversity is a relatively young domain, founded in the work on island biogeography. The rapid loss and fragmentation of habitats because of human activities has further increased the interest in spatial ecology, and has fostered the study of metacommunity dynamics. A metacommunity is defined as a set of local communities that are linked by dispersal. For single species, the metapopulation concept addresses how dispersal connecting a set of local populations can compensate for local extinction and enable the regional persistence of a species. While explicitly addressing different spatial scales, the metapopulation concept ignores that species may affect each other’s birth and death rates. Metacommunity ecology explicitly addresses interactions among species at different spatial scales and addresses how species interactions can influence or be influenced by spatial dynamics. Thereby, the concept of metacommunities combines two common features of many biological systems, namely that species are interacting in complex ways and that spatial heterogeneity and fragmentation leads to fragments of suitable habitat patches in a matrix of non-habitat. Importantly, species interactions can affect spatial processes, and vice versa. Current interest is mostly in understanding which types of interactions are occurring at different spatial scales, and understanding the relative importance of species interactions and dispersal in shaping natural communities. The speakers will give an overview in classic approaches of spatial ecology, specifically focusing on the metacommunity concept. They will highlight current research foci, especially combined evolutionary and ecologically dynamics in spatial ecology.

Formulating and Fitting Mechanistic Models
In this session we will attempt different modelling paradigms for formulating and fitting mechanistic models. We are all aware that there are a lot of options out there. Stochastic versus deterministic, ODEs, PDEs, difference equations, individual based models, Bayesian inference versus least squares. I have used most of them in my time and hopefully you will too. What is critical is to not let the research with the models drift too far away from the real world. Here we will attempt these different paradigms and identify ways we can work to prevent replacing a world we are attempting to understand with models that we don’t understand.