Here you will find a description and further details for each of the proposed theses themes.
T1. Evolution of heterocarpic plants
T1a - Along a gradient of environmental unpredictability (i.e. an aridity gradient in Israel), the ratio of far vs. short dispersing seeds should change: more seeds with high dormancy should be produced towards the arid. There should be a trade-off with dispersal, i.e. dispersal distance and seed dormancy should be inversely related. This hypothesis will be tested using a collection seeds from of annual heterocarpic species. They will be grown in Winter 2019/20. Start: Sept-Nov 2019 (preparation), peak work March-May 2020 (i.e. between Nov and March there is time for taking courses).
T1b - Plasticity should be more pronounced for plants coming from more variable (i.e. arid environments). Thus we assume that plants will plastically change the ration between the two seed morphs more when coming from arid sites. This hypothesis will be tested with growing several species of annual plants from an aridity gradient under drought and well-watered conditions. Start: Sept-Nov 2019 (preparation), peak work March-May 2020 (i.e. between Nov and March there is time for taking courses)
T2. Evolution of flowering time under climate change
A recent PNAS paper says that phenology response, i.e. early flowering, to increasing temperatures could be an indirect effect of (increasing) competition. However, this study assumed that as temperatures rise, competition will become more intense. Yet, this should only be true for temperate regions. In hot and dry environments, warming would decrease densities, i.e. in deserts, temperature alone can be a cue for early flowering. We hypothesize that competition delays flowering in plants from dry and hot environments but not in plants from temperate or cool environments.
This should be done in two separate studies- one starting in March 2019 and one in October/November 2019 with species from temperate and desert origin.
T3. Competition intensity and relatedness
In an equilibrium world, coexistence requires that plants differ from each other. Therefore, competition should be stronger between plants that are very similar. Thus, competition intensity should increase along a gradient of relatedness, ranging from between regions, between family within a region, between species within a family, between individuals within a species from different climates, between individuals from same climate and species, between sibling plants. relatedness should also affect symmetry of interactions and should be more symmetric on an intraspecific level.
This topic is more relevant for an MSc level and will be tested with the collection of Israeli annuals, i.e. this is again a winter topic.
A1. Can my enemy turn into a friend?
It has been shown that metal hyper-accumulation evolved as a strategy to reduce the performance of competing neighbouring species via the release of heavy metals. We hypothesize that whether this defence mechanism against neighbours results in a net negative effect (competition) or a net positive effect (facilitation) between the interacting plants depends on the presence/absence of herbivores, as well as the concentration of heavy metals in the soil. Our hypothesis will be tested with simulation experiments using an individual-based modelling approach. The goal of this master's thesis is to disentangle the different indirect species interactions at hand, to pinpoint the conditions for coexistence of hyper-accumulating and "normal" plants, and to inspire targeted experiments.
The supervision will be shared between Anubhav Mohiley and Korinna Allhoff. The earliest start would be in October 2019, but only, if the candidate already knows how to set up an individual-based model. Otherwise we plan to start in January 2020, with the compulsory condition that the candidate signs up for the Computational Ecology course held by Korinna Allhoff in the winter semester (course number 4210, registration via Campus). In the latter case, there is no special prior knowledge required. The total duration of the project is 6 months, which can be extended in a very flexible way in case the candidate can not work full-time.
R1. Can plant biodiversity and habitat heterogeneity be seen from the sky?
Topic: UAV-carried vegetation sensors have boosted the application of multispectral remote-sensing techniques for the collection of small-scale, high resolution vegetation data. Yet, little is known about the feasibility of these technologies to assess aspects of species diversity and/or plant functional traits. The offered thesis seeks to study and promote the applicability of this technology to accurately assess, estimate and predict important plant community metrics in near-natural vegetation of central Europe. The thesis involves field work at the Heuberger Tor, as well as image processing and analysis in the IT-lab.
Starting date / duration: April/May 2019, 6 months
R2. Is spectral diversity related to biodiversity and habitat heterogeneity?
Topic: Vegetation canopies absorb and reflect electromagnetic radiation just as any other physical object. These vegetation spectra are related to species’ physiology and traits (e.g. leaf pigments and texture). The spectral variation hypothesis proposes that spectral diversity, i.e. the diversity in the reflectance-absorbance measurements of a vegetation stand, is related to species diversity: More diverse vegetation should show more diverse spectra. We want to test this hypothesis in an established field-experiment at Heuberger Tor. Thesis work involves field work as well as image processing and analysis in the IT-lab.
Starting date / duration: April/May 2019, 6 months.
Currently all proposed theses topics supervised by Maja have been taken, but please come back to check for new opportunites from time to time.
Currently all proposed theses topics supervised by Maxi have been taken, but please come back to check for new opportunites from time to time.