Institut für Evolution und Ökologie

Upcoming theses (MSc and BSc) opportunities

Here you will find a description and further details for each of the proposed theses themes.


A) Evolution of heterocarpic plants

Many composites produce two or more types of seeds which differ in dispersal and germination characteristics. This heterocarpy is considered a type of bet-hedging strategy whereby different seed morphs are produced in environments which are spatially and/or temporally variable.

A1) 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 2021/22. Start: Sept-Nov 2021 (preparation), peak work March-May 2022 (i.e. between Nov and March there is time for taking courses).

A2) Plasticity should be more pronounced for plants coming from more variable (i.e. arid environments). Thus we assume that plants will plastically change the ratio 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 2021 (preparation), peak work March-May 2022 (i.e. between Nov and March there is time for taking courses)

B) 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 a winter topic (Nov-May).

C) Plant-soil feedbacks

Plants can modify the microbial community in the soil they are growing in and very often, there are negative plant-soil feedbacks. These result in intensified intraspecific negative interactions and have thus been proposed as a mechanism promoting coexistence among species. Plant-soil feedbacks have also been studied in the context of invasion biology, i.e. studies have tested whether conditioned soil may inhibit invasion.

In this topic, we can make use of a huge common garden experiment with 2800 pots that were conditioned with altogether 30 common grassland species. We would like to start a pilot study in Spring 2020, probably with Arabidopsis thaliana as this species grows fast and has no mycorrhiza, i.e. we can rule out positive plant-soil feedback effects. We could then also make a larger experiment where we test the use of native species for suppressing common invasives such as Solidago canadensis or Impatiens glandulifera.

D) Plant-microbe interactions under climate change

Climate change in our region is predicted to generate a higher frequency of extreme drought events. This may affect organisms directly, by decreasing resource availability, or indirectly, by modifying organismic interactions. This project, which is embedded in a long-term experiment entitled ‘Drier’, aims at studying the change in the microbial community associated with common grassland plants, when these are exposed to extreme drought events in the field.

Methods: The microbial community of several common grassland plant species has been sampled in Summer 2020, after a 1- to 3-year drought in a long-term field experiment. The first step in this project is to characterize this community in terms of differences among plant species and drought treatments. This will be done by high-end molecular methods, and will be mostly conducted in the lab of Eric Kemen (ZMBP).


Contact Max Schmid

A) Could competition help species to cope with environmental change (Master thesis)?

Background: Species are repeatedly confronted with large-scale environmental changes that force them to adapt and evolve their phenotype. How fast evolution can happen depends on range of characteristics, for instance  the extent of genetic diversity, the life history of species, or the details of the selection process. Recent theoretical studies further indicate that ecological interactions could shape the speed of evolution. For instance Osmond & Mazancourt (2013) described a situation where competition might have a positive effect on the rate of evolution, despite being a negative ecological interaction between individuals. Our understanding of how competition might affect the speed of evolution, however, is limited and asks for further investigations.

Aims and Methods: This Master project aims to better understand how competition for resources might speed up evolution in consumers and helps to rescue populations from extinctions. You will build computational models (i.e. individual-based simulations) to simulate evolution in silico and explore the model behavior systematically.

What you should know: For this project, it would be beneficial if you are familiar with programming in R (or another programming languages). Ideally, you are further not afraid of mathematical equations and you are fascinated by fundamental ecological and evolutionary processes and environmental dynamics. Nevertheless, far-reaching mathematical knowledge or professional programming skills are not needed! There is no specific time constraint and you could start at any occasion.

 

B) How stable is biological diversity in face of environmental change (Master thesis)?

Background: Biological diversity is one of the most fundamental topics in ecology and evolution. How biological diversity evolves, however, is still subject of ongoing research. While we made substantial progress in our understanding of which processes favor the evolution and maintenance of biological diversity, we know much less on the stability of diversity in face of directional environmental changes. In particular, we do not know whether the different drivers of diversity (spatial environmental variation or competition) also lead to different levels of stability when biologically diverse populations are confronted with directional environmental changes.

Aims and Methods: In this Master project, you will analyze the stability of biological diversity at the example of resource competition. Here, we have a good understanding of how diversity in resources favors diversity in consumes, but we do not know how different mechanisms shape the stability of consumer diversity. You will study this question by the use of individual-based simulations and model evolution and environmental change in a computer model.

What you should know: For this project, it would be beneficial if you are familiar with programming in R (or another programming languages). Ideally, you are further not afraid of mathematical equations and you are fascinated by biological diversity and its underlying mechanisms. Nevertheless, far-reaching mathematical knowledge or professional programming skills are not needed! There is no specific time constraint and you could start at any occasion.


Contact Sara Tomiolo

A) Disentangling physical and chemical effects of plastic contamination in soil on plants (master thesis)

Background: Plastic contamination in soil is considered to be an emerging global stressor that may affect plant performance and plant-soil interactions. However, given the relatively low number of studies on the topic and the highly context-dependent effects of plastic on soil and plants, it is difficult to make clear predictions.

One hindrance in our understanding the effects of plastic contamination on soil and plants, is that we cannot yet disentangle the physical and chemical effects of plastic particles on soil and plants. Plastic fragments can affect soil aggregation, but they can also leach chemicals in soil that affect plant and soil biota performance.

Aims and Methods: The project aims at disentangling the chemical and physical effects of plastic particles on plant and soil, by means of a greenhouse experiment. These results will provide a proof of concept for further guiding future field and greenhouse studies.

What you should know: We are searching a highly motivated student with a good knowledge of experimental design and of statistical analyses in R, or a strong scientific interest in plant ecology, plant soil interactions and environmental sciences. 

Please contact Sara Tomiolo if you are interested or if you have further questions.

B) Effects of microplastic on root development (Bachelor thesis)

Background: Microplastic contamination in soil can affect soil aggregate stability and water balance, thus potentially affecting root development and growth. On the other hand, by diminishing soil resistance and increasing the proportion of soil channels, it can also facilitate root growth. However, little is known about the direct interactions between plastic fragments and roots. Plastic fragments leach chemical in soil and attract a specific set of microbes that can be different from those in the surrounding soil. This may have an impact not only on root growth, but also on root branching and development.

Methods and aims: to test how plastic contamination in soil affects early root growth and development, we will use transparent containers that allow monitoring root growth and development overtime.

What you should know: We are searching for a highly motivated student enthusiastic about plant ecology and plant soil interactions. The candidate should have attended plant ecology 1 or an equivalent course and should have a solid understanding of basic statistics. Some knowledge of the statistical software R is a plus.

Please contact Sara Tomiolo if you are interested or if you have further questions.