Stress Responses and Adaptation in Aquatic Plant Communities

In a series of glasshouse and lab experiments, we are seeking to understand how diversity and evolution interact and enable duckweed populations to persist in stressful environments. The aim is to test whether either diversity or evolution (or both) can rescue these aquatic plant communities. We are using different locally relevant stressor and duckweed populations collected in the wild. Some completed and running projects are summarized below.

Recently, we looked at the genetic differences and how populations are structured for 23 different groups of Lemna plants found naturally in Switzerland, using whole-genome sequencing. We used two different ways to analyze the data. One method did not rely on any previous genetic information (called reference-free kmer approach), and the other method did (using two different reference genomes). From these analyses, we found two main groups, which matched up with different species. The first group had the L. minor plants we were studying, and the second group had plants from a hidden species called Lemna japonica. We thus revealed that Lemna japonica is much more widespread than previously thought. Read the preprint here!

As one of the first experiment using the speces Lemna minor as model system, I tested the importance of intraspecific (ecotype) diversity on population abundance. I found that as the environment deteriorated, mainly due to algal stress, higher ecotype diversity resulted in greater duckweed abundances. The results are published in Journal of Plant Ecology (open access).

For her Master thesis, Sofia Vámos searched for local adaptation signals in four populations of Lemna minor, collected from the four corners of Switzerland. Her M.Sc. thesis is published in Nordic Journal of Botany. We found that L. minor was highly tolerant towards the heavy metal pollutant zinc, but we could not find evidence that any of the four populations were locally adapted. Have a look at the paper here!

In a lab experiment led by my former BSc student Lorena Lanthemann, we tested whether the presence of a second species influenced the growth rate of the three duckweed species Lemna minor, Lemna gibba, and Lemna turionifera. We used four different Zn concentrations in a replicated microcosm experiment under sterile conditions, either growing the species in isolation or in a 2-species mixture. This work is published in Ecology and Evolution (open access). You can find it here.

Based on fieldwork I did back in 2019 in Montreal, we studied the effect of the natural microbes associated with duckweed on its fitness: Presence of the microbiome decreases fitness and modifies phenotype in the aquatic plant Lemna minor. We show that the aquatic plant Lemna minor has higher fitness when we removed their microbiome. This was the case for eight different genotypes and across several environmental conditions. We also found that the presence vs absence of the microbiome modified the plant phenotype. Check out the paper published in AoB Plants here!