Key questions: What is the relative importance of dispersal and dispersal diversity compared with other processes for species coexistence and functioning of metacommunities? How do temporal dynamics in dispersal via matrix corridors or mobile links affect biodiversity maintenance? How strong is the impact of land-use change on community structure and functioning via the modification of environmental parameters vs. dispersal dynamics?
Background, methods and work plan: This tandem-PhD-project will use the unique system of kettle holes (infield ponds) of the AgroScapeLab-Quillow as a model system to assess the significance of dispersal processes for the structure of natural communities These ponds contain zooplankton communities connected by dispersal via wind and biological vectors such as insects and birds through the surrounding agricultural matrix, thereby forming landscape-scale metacommunities. Temporal corridors resulting from dynamic changes in the agricultural matrix may affect dispersal for example via influencing mobile links. Furthermore, agricultural practices likely have an impact on local community structure by altering environmental conditions. However, dispersal strategies and frequencies vary between species and species coexistence may ultimately be stabilized by this dispersal diversity.
The work plan of the PhD 1 (P07: landscape-scale patterns) will consist of the following steps: (i) We will characterize local environmental factors such as chemical and physical water parameters, nutrient concentrations and pond size and the zooplankton communities in selected ponds distributed across the landscape. We will analyse spatial signals in individual species distributions and in community structure likely representing dispersal processes. For example, we will assess the relationship between community similarity and the distance and matrix structure between ponds. We will furthermore integrate data on dispersal rates and distances measured by PhD-project 2. (ii) We will then select target taxa for which resting stages can be extracted from sediment cores. These taxa will be closely related Brachionus rotifer and Daphnia cladoceran species, which are frequently used in temporal studies. With genetic analyses of sediment samples from the last centuries, i.e. barcoding of genes suitable for ancient potentially degraded samples (cytochrome oxydase I [CO I]), we will be able to compare the current and historical genetic diversity and species composition at landscape-scale and to infer the contribution of dispersal to local populations by evaluating the spatial component in genetic and community composition across time. (iii) In addition, clonal populations originating from resting eggs will be set up so that morphological and physiological traits can be examined and trait compositions compared through space and time.
In parallel, PhD 2 (P08: detailed movement processes) will assess the influence of species-specific (deterministic) variation in dispersal strategies on community composition and functioning via stabilizing effects. The work plan consists of four steps: (i) We will directly measure dispersal rates, directions and distances and their temporal variation at landscape-level for aquatic organisms that likely differ in their dispersal strategies (e.g. wind-dispersed, vector-dispersed or flying species). We will use automated suction traps and sticky traps set up in spatial grids in the landscape between kettle holes and record the number and species identity of dispersers and thus assess dispersal rates and distances. (ii) We will assess the role of biological dispersal vectors as mobile links affecting the structure of zooplankton communities. Specifically, we will capture water birds to collect data on individual movement based on GPS-telemetry and colour-ringed individuals. In addition, we will collect samples of zooplankton resting stages and insect eggs from the feathers of the captured birds. (iii) We will design lab experiments using multispecies zooplankton communities that are set up within realistic ‘micro-landscapes’. These communities of selected species extracted from the field site will be kept in Erlenmeyer flasks that will be connected by experimentally controlled dispersal, implicitly mimicking dispersal processes across landscapes as derived from the field studies in steps (i) and (ii). We will use species-specific dispersal rates and will manipulate the spatial arrangement of communities in terms of their connectivity. (iv) We will then use dynamic metacommunity models to predict the outcome of different realistic dispersal scenarios based on data obtained from our field and lab studies.
Innovation and link to overarching questions: Overall, this project will quantify the importance of dispersal diversity, temporal dispersal dynamics and mobile links for the diversity and functioning of aquatic metacommunities and assess the impact of land use change on dispersal-related mechanisms of species coexistence. We will address several key questions of the overarching BioMove concept.