Supervising team: Florian Jeltsch, Volker Grimm, Stephanie Kramer-Schadt
Workplace: University of Potsdam
0. Brief expected profile of PhD student
Candidates must have a MSc in Ecology or related fields. Candidates with a modelling background from other natural sciences will also be considered. Experience in process-based mathematical or simulation modelling is required. A solid background in community ecology is desirable.
1. Short Abstract
This project will develop and apply a novel approach to dynamically model vertebrate community changes in heterogeneous dynamic landscapes. Based on an allometric approach home range dynamics of a large number of competing individuals will be simulated under different scenarios of habitat loss, fragmentation changes, and resource dynamics. The new model will allow exploring the role of (i) individual movement and space use during foraging, and (ii) juvenile dispersal for biodiversity dynamics under changing environmental conditions.
2. Background and previous work
Movement rules of individuals define the space use of species since they determine how individuals use their heterogeneous environment. At the biodiversity level, it is therefore essential to identify the key factors influencing individual movements in response to habitat characteristics and land-use changes, which ultimately alter resource availability such as food and shelter. However, inferring from individual space use to community composition and biodiversity is challenging given the high number and variability of individual organisms and the complexity of their spatio-temporal interactions. A novel individual-based, spatially-explicit but static modelling approach to this problem was introduced by Buchmann et al. (2011, 2012, 2013). Using an allometric approach to parameterize key aspects of organisms (e.g. movement costs) the authors simulated home-range formation of competing vertebrates in fragmented resource landscapes. In the first PhD-cohort of BioMove project 11 this static modeling approach was adapted to investigate the consequences of landscapes of fear on prey community metrics (Teckentrup et al. submitted). The model scaled up from individual home range formation based on food availability and perceived predation risk to consequences on prey community structure and composition. This mechanistic approach allowed us to explore how important factors such as refuge habitat availability and foraging strategy under fear affect prey community metrics. Findings revealed that non-consumptive predator effects can have important implications for prey community diversity and should therefore be considered in the context of conservation and nature management.
The next important step in this novel modelling concept will be the model extension towards populations and community dynamics in changing landscapes. This includes reproduction and mortality but also the dispersal of juveniles which adds another important explicit movement process that is likely to impact biodiversity dynamics.
The proposed new study will lead to a new way of scaling up from individuals to vertebrate biodiversity pattern under dynamic environmental conditions. Following a trait-based (i.e. largely allometric) strategy allows for reducing the inherent complexity involved in dynamic individual-based models at the community level. In particular, this project aims at following key objectives:
- Identifying the biodiversity stabilizing capacity of adaptive home range formation under dynamic scenarios of (i) increasing fragmentation, (ii) habitat loss, (iii) landscape level resource changes in time and space (e.g. related to land use)
- Revealing possible stabilizing effects of juvenile dispersal in changing landscapes.
4. Outline work program
In a first step the PhD student will re-implement and expand the existing individual-based home-range model by Buchmann et al (2011, 2012, 2013) and Teckentrupp et al (submitted) using C++ programing language. The existing static home range model will be developed into a dynamic model simulating key processes of spatio-temporal community dynamics at the level of individual organisms (mammals or birds) that compete for resources. The important step towards a dynamic simulation model makes it necessary to implement additional, new processes. These include reproduction and juvenile dispersal (and juvenile home range formation) as well as immigration and emigration. Previously static landscape scenarios will be substituted by scenarios of dynamic landscape changes. The new model will be systematically evaluated in a thorough sensitivity analysis.
The strict home-range oriented approach in this project allows the simulation of a high number of individuals and species but is necessarily coarser than the modelling approach in project P01 that focusses on the explicit movement pathes and memory of interacting individuals. Both approaches complement each other and will allow for systematic comparisons.
In a second step we will make use of a theoretical strategy using fractal landscapes with defined levels of fragmentation and habitat characteristics. Dynamic landscape scenarios will systematically vary available resource patches, degree of fragmentation and temporal resource dynamics. Based on these landscape scenarios, the PhD student will systematically explore the potentially stabilizing effects of adaptive home range formation for different foraging strategy types (e.g. central place forager, nomadic forager) and vertebrates (mammals, birds).
In a third step the movement-related process of juvenile dispersal will be explored in relation to its potentially stabilizing effect on the vertebrate biodiversity. We hypothesize that, depending on the specific movement rules, the dispersal of successful offspring can provide a buffering mechanism against population decline and community changes.
Depending on data availability the modeling approach will be adapted to real systems in a fourth step of the PhD study. Different data will be used for model parameterization and for model evaluation. Applying an observer-biased subsampling of simulated data model outputs will be systematically compared with empirical data from the specific study system. Comparable outputs include explicit patterns of home range distributions (e.g. size distributions or spatial distribution in the study landscape), or community composition and structure (e.g. including relative abundance of species with given body mass at habitats with defined level of fragmentation).
5. Linkage to ‘BioMove’ hypotheses, objectives and concepts
This project connects the ‘bottom-up’ and the ‘top-down’ clusters of BioMove and addresses two of its focal hypotheses (H1*, H3*). It will further allow testing the linked hypotheses that (i) the adjustment of individual movements in response to changes in resource availability/ distribution and during juvenile dispersal leads to a reorganization of home range patterns at the community level, and (ii) that these plastic processes provide stabilizing mechanisms (see conceptual BioMove framework) that can buffer against negative effects of land use and landscape changes. It will further shed light on the role of specific landscape features (e.g. amount and fragmentation of resources and shelter habitat) for the strength of these stabilizing effects.
*H1: Movement variation and behaviour-mediated adaptability act as equalizing and/or stabilizing mechanisms for species coexistence.
*H3: Non-linear feedbacks in foraging movement behaviour provide equalizing and/or stabilizing mechanisms for species coexistence.
1) Buchmann CM, Schurr FM, Nathan R, Jeltsch F (2011) An allometric model of home range formation explains the structuring of animal communities exploiting heterogeneous resources. Oikos 120: 106-118.
2) Buchmann CM, Schurr FM, Nathan R, Jeltsch F (2012) Movement upscaled – the importance of individual foraging movement for community response to habitat loss. Ecography 35: 436-445.
3) Buchmann CM, Schurr F, Nathan R, Jeltsch F (2013) Habitat loss and fragmentation affecting mammal and bird communities - the role of interspecific competition and individual space use. Ecological Informatics 14: 90–98.
4) Teckentrup L, Grimm V, Kramer-Schadt S, Jeltsch F (submitted) Community consequences of foraging under fear.