Supervising team: Volker Grimm, Melanie Dammhahn, Christian Voigt, Florian Jeltsch
Workplace: University of Potsdam/UFZ Leipzig
0. Brief expected profile of PhD student
The candidate must have a master or equivalent degree in any natural sciences or mathematics, and have sound experience in programming, statistical analysis of data, and, preferably, in the design and analysis of computational models. A background in behavioural ecology and/or community ecology is desirable.
1. Short Abstract
Intra-specific trait variation (ITV) has received much attention in behavioural ecology (i.e. animal personality) and ecology (e.g. individual niche specialisation) alike and is increasingly recognized as a key element of species persistence and coexistence. While variation in age and size has already been explored, the consequences of variation in behaviour and in particular in movement have so far been largely ignored. Therefore, a spatially explicit individual-based model of two or more competing species will be developed, which live in habitats of varying levels of spatial heterogeneity. Intra-specific variation in movement-related traits will be implemented, in particular the personality traits activity, exploration and boldness. Consequences of these trait variations for space use, population growth rates, and species coexistence will be explored. The model’s design will be generic but also allow representing rodents, e.g. bank vole and the striped field mouse. Experiments on these species in P01/Cohort 1 of BioMove will provide data for informing model design and testing. Community models based on habitat-based home range formation developed in P11/Cohort 1 will serve as a reference, which implies also exploring how ITV in predator avoidance affects coexistence.
2. Background and previous work
Until recently, ecological modelling has mostly ignored ITV and rather considered average individuals or represented variation only stochastically, via demographic noise. While ITV in age and size received some attention, ITV in behavioural traits was ignored, even in most early individual-based models, which still imposed behaviour instead of letting it emerge from the individuals’ traits. More recently, both individual-based modelling and our ability to track ITV in behaviour enable us to explore the consequences of ITV for species persistence and coexistence. The guiding hypothesis of this project is that ITV in movement behaviour matters, i.e. it makes a difference whether interactions between two or more species are between identical individuals of each species, or between individuals with different traits. Differential movement of individuals can be a key mechanism generating spatial and temporal patterns of interacting individuals, populations and species. Individuals in natural populations vary consistently in their expression of various ecological, physiological and behavioural traits and such intra-specific variation has important consequences in shaping ecological communities.
The project will develop generic mechanistic models that are informed by patterns observed in the experiments in P01/Cohort 1, where intra-specific variation in attributes of movement behaviour, such as exploration and boldness, were demonstrated both for isolated and interacting individuals. Conceptually, the model will be related to the community model of P11, where home ranges of individuals varying in body mass were packed into a landscape to explore the effects of different behavioural attributes regarding predator avoidance (“landscape of fear”). Those home ranges were “habitat-based” (R. Zakrzewski, unpubl. thesis) in that individuals keep adding spatial units to their home range until requirements regarding resources or shelter are satisfied. In the new project P01/Cohort 2 we will use the alternative “memory-based” approach, where individual space use and corresponding home ranges emerge from the fact that animals tend to return to places they visited before because they were favourable. Both types of models are driven by different kinds of data: habitat-based models use maps as input whereas memory-based models use movement tracks. Both model types can overlap, so that synergies between P11 and P01 are to be expected.
The overall objective of this project is to understand how ITV in movement-related behaviour, in particular activity, exploration, and boldness, affects population persistence and species coexistence. More specifically, the objectives are:
4. Outline work program
First, a generic individual-based model based on rodent movement will be developed. The model will be based both on memory, i.e. individuals are assumed to memorize good and bad habitat, or just places which they liked for whatever reason, and use this memory to return to preferred sites and avoid undesirable sites. This single species work is challenging and novel enough to warrant a first publication. A specific focus of this work will be implementing different movement traits, such as activity, exploration, and boldness, and different habitats, both for populations with and without ITV in these traits. Data from P01/Cohort 1 will be used to parameterize these traits.
Second, the model will be extended to two or more hypothetical species. Scenarios will be implemented to systematically understand how ITV could affect species coexistence, for example via equalizing mechanisms. Both invasion experiments and community assembly will be implemented. The models will be generic at first and based on general principles, expert knowledge, and the literature. Additionally, data and lessons from P01/Cohort 1 will be used to narrow down parameter ranges and sets of possible submodels representing movement.
Third, the community model of the second step will be related to the community models developed in P11 to explore how differences in representing home ranges affect population dynamics, coexistence, and spatial distribution, and how including ITV in movement responses to predators act as stabilizing or de-stabilizing mechanisms.
5. Linkage to ‘BioMove’ hypotheses, objectives and concepts
BioMove aims at linking movement ecology and biodiversity research. This requires an individual-based perspective because movement is affected by species identity, individually experienced habitat features, and interactions between individuals. ITV is an additional dimension to explore. It is increasingly discussed in ecological research, but so far there is no general agreement on its importance for species coexistence. There are arguments and modelling studies supporting both, strong and negligible effects of ITV on coexistence. However, none of these studies has represented movement in the detail required by movement ecology. This project will thus fill an important gap. The project is driven by the hypothesis that a true and predictive integration of movement ecology and biodiversity research requires representing both ITV in movement and relevant spatio-temporal dynamics of habitat quality and features, such as predator presence or cover.