Supervising team: Niels Blaum, Jana Eccard and Stephanie Kramer-Schadt
Workplace: University of Potsdam
0. Brief expected profile of PhD student
The candidate should have a background in Movement-, Landscape- and Behavioral Ecology, with an excellent MSc in Ecology or related discipline. Experiences in capturing and tagging animals with GPS collars, analyzing big data sets (GPS tracking and acceleration data), and in applying advanced statistical methods (random forest, movement networks) are strongly preferred.
1. Short Abstract
Mobile links connect different kinds of habitat patches, thereby affecting biodiversity. This project analyses, how specific animal-landscape-conditions (internal status of mobile link, landscape complexity, predictability of resources) affect the amount and frequency of mobile links critical for biodiversity. We will GPS-collar European brown hares (Lepus europaeus), a typical species in agricultural landscapes that provides genetic links (seed dispersal) and process links (foraging on potentially rare plant species). Network based tools will be applied for mobile link analysis (see below).
2. Background and previous work (focus on Project P03 - cohort 1)
Mobile links are essential components of landscapes. Their individual movements across transient matrix corridors connect different kinds of patches (ecosystems or fragments of it, biotopes, but also agricultural pastures) and can affect biodiversity dynamics (1, 2). Small scale movements at the home range scale are the key mechanisms of animals to respond to changes in resource availability. The extent and frequency of these movements are determined by the internal status of the focal organism (e.g. hunger, searching for mate), and the interaction between the spatio-temporal pattern in resource availability (e.g. timing and synchrony of plantation, growth and harvesting of crops) (3). These dynamic interactions strongly affect the realized movement paths of mobile links that may be critical for biodiversity. The first PhD analyzed how the spatial and temporal variability of resources in agricultural landscapes affects home range size of the European brown hare in relation to landscape structure (complex landscape: small field sizes (~2.9ha), many landscape elements e.g. hedge rows, tree stands and fallow land versus a simple landscape with large field sizes (~27.5ha), few elements). The results show that only hares in simple landscapes increased home range sizes with increasing resource variability leading to an increase in mobile link functions (4). Surprisingly, in both landscapes, home range adjustments to unpredictable resource changes caused by sudden mowing or harvesting activities are less clear. Home ranges increased or decreased in size, but also no changes were recorded (Ullmann et al. in prep). This suggests that home range size alone is insufficient for estimating mobile link functions in unpredictable landscape conditions. Here, the number of the connected habitat types and the frequency of these connections within a home range are probably more relevant for mobile link functions and therefore critical for biodiversity dynamics. Still, both may be completely unrelated to home range size adaptations. In any case, the number of connected patches and frequencies of connections may affect different types of mobile links. While the PhD in cohort 1 focused on genetic links (seed dispersal) showing that mainly seeds of common species are moved between patches (e.g. Cerastium holosteoides, Deschampsia cespitosa, and Poa annua), potential process links (foraging on rare plant species such as Betonica officinalis, Scabiosa, columbaria, Pedicularis palustris) have not been considered yet.
The key objectives of the second PhD in P03 are
(i) to quantify changes in amount and frequency of both genetic and process links in relation to specific hare-landscape-conditions (internal status of hares, landscape complexity, species richness of grassland fragments, and predictability of resources),
(ii) based on the tagging of new individuals to record hare locations with a high temporal resolution (PhD 1: one location/ hour; PhD 2: one location/ 4 mins) and 3D-acceleration, may allow for predicting movements and mobile link functions, and
(iii) to estimate the potential of hares as process link (i.e. foraging on rare plant species).
4. Outline work program
The work plan of the PhD is divided into field work and extensive analysis with new methods:
Field work (year 1): hares will be captured and tagged with GPS collars with internal acceleration sensors in areas with high and low diversity of grassland fragments (based on existing vegetation data). We will apply a high temporal resolution of hare GPS locations (1 location/ 4 mins) and acceleration data for detailed analyses of small scale movements within home ranges. Resource availability and variability will be quantified by monitoring crop specific growth and timing of management. Hare feces will be collected for germination experiments to identify genetic links (seeds) (MSc-thesis 1), stable isotope analyses to define the nutritional niche, or (iii) DNA-Metabarcoding to identify foraged plant species (MSc-thesis 2).
Movement data analysis (year 2-3): The existing data of 60 hares from PhD 1 (109.668 GPS locations and 2.912.400 acceleration measurements) will be complemented by new high-resolution GPS and acceleration data from PhD 2. Using this exceptional big data set, we will apply network-based tools to analyse changes in amount of genetic and process links and the frequency of their spatial connectivity (5). Movement networks within individual home ranges to identify the exact location of hare activity centres (nodes) and movement paths (edges), and frequencies between these nodes. Behavioural networks based on the behaviour-specific acceleration pattern analyses of PhD 1 (e.g. resting, foraging, running) and new acceleration data of PhD 2 will allow quantifying the amount of genetic and process links and the underlying behaviour for movements between the patches in relation to the specific hare-landscape-conditions. Optional field work (MSc-thesis 3): After spatial identification of nodes, plant diversity can be estimated at the nodes and compared to random locations of the same habitat to estimate the relevance of plant diversity for the position of nodes.
5. Linkage to ‘BioMove’ hypotheses, objectives and concepts
This project will analyse how the specific landscape context and human impact of agricultural landscapes affect (i) the spatial and temporal scale of movement paths and behaviour of a mobile linker (general research questions Q4 and Q5) and (ii) the scale, at which potential links may influence local plant diversity (Q6-Q7). Integrating a strong temporal aspect of landscape dynamics and individual movements we aim at a more mechanistic understanding of the linkage between short-term land-use effects, individual movement responses, and its potential consequences for biodiversity-relevant genetic (seed dispersal) and process links (foraging on rare plant species). This will help to refine the mobile link pathway of the BioMove concept.
(1) Lundberg J & Moberg F (2003). Mobile link organisms and ecosystem functioning: implications for ecosystem resilience and management. Ecosystems 6: 87-98.
(2) Jeltsch F. et al. (2013). Integrating movement ecology with biodiversity research-exploring new avenues to address spatiotemporal biodiversity dynamics. Movement Ecology 1:6.
(3) Van Moorter B, Bunnefeld N, Panzacchi M, Rolandsen CM, Solberg EJ & Sæther BE (2013). Understanding scales of movement: animals ride waves and ripples of environmental change. Journal of Animal Ecology 82: 770-780
(4) Ullmann W, Fischer C, Kramer-Schadt S, Pirhofer-Walzl K & Blaum N (submitted). Spatiotemporal variability in resources affects herbivore home range formation in structurally contrasting and unpredictable agricultural landscapes.
(5) Jacoby MP & Freeman R (2016). Emerging Network-Based Tools in Movement Ecology. Trends in Ecology & Evolution 31: 301-314.