English 2019-04-09T12:03:17+02:00



This is the website of Ger Boedeltje, scientist, ecological consultant and (former) teacher.

The name of the consultancy “Daslook” refers to Allium ursinum, in English Wild Garlic or Bear’s Garlic .

Background and experience
I am an ecologist experienced in aquatic, semi aquatic and terrestrial ecosystems. My work includes, among others: 1) research of plant dispersal in rivers and canals, 2) vegetation research, 3) analyzing and evaluating ecological data, 4) development and giving of ecological courses, 5) making designs for constructed shallow zones along waterways, 6) writing and reviewing of scientific papers, and, recently, 7) doing research on endochorous seed dispersal by fishes and, currently, 8) on hydrochorous dispersal of forest plant species.

My specialties include hydrochory, seed dispersal, endozoochory, vegetative plant dispersal (figs 1, 2), seed bank research in aquatic systems, biogeochemistry of aquatic systems, analysis en evaluation of ecological data, aquatic plants, (nature) education and courses and reviewing reports and papers.

Figure 1. Elodea nuttallii, Elodea canadensis and Callitriche obtusangula largely rely on vegetative dispersal.


Figure 2. Nuphar lutea spreads both generatively (above) and vegetatively (below).


Present work
My present work includes, among others: 1) monitoring and evaluating ecological restoration projects in streams, 2) analyzing and evaluating ecological data, 3) development and teaching courses on aquatic plants, 4) making designs for constructed shallow zones along waterways and 5) working as guest researcher at the Institute of Water and Wetland Research of the Radboud University in Nijmegen.

Plant dispersal by fish
As a researcher, I recently finished, with others, a paper in which the role of both seed traits and fish traits in the propensity of seeds for fish-mediated dispersal was studied. Seeds of 19 aquatic plant species (varying in size, mass, hardness, mucilaginous coat and appendices) were fed to common carp (Cyprinus carpio) and Mozambique tilapia (Oreochromis mossambicus), which have contrasting adaptations to feeding. Carp has a pharyngeal ‘mill’, compensating for lack of both stomach and oral jaw teeth, while tilapia has many small pharyngeal teeth and an acid stomach. We could demonstrate that the probability of seed ingestion, retrieval after gut passage and germination and viability after gut passage was affected by both fish and seed traits. In 2015, this paper was published in Freshwater Biology. The movies hereafter show the feeding of seeds (hidden in dough balls) to both common carp and Mozambique tilapia.

Feeding of Common carp


As a follow up, I published together with Eelke Jongejans, Tom Spanings en Wilco Verberk a paper in Aquatic Botany (2016), in which we focused on the effect of gut passage in fish on the germination speed of aquatic and riparian plants.

Dispersal of forest plant species

In 2015 and 2016, I studied the potential contribution of water currents to long distance dispersal of forest species. In this study, I quantified the transport and deposition of generative and vegetative propagules in a forested lowland stream (Boven Slinge, Winterswijk, The Netherlands; figs. 3 and 4). The diversity and abundance of the diaspores trapped will be related to species’ occurrence in the forested species pool and to specific life-history traits of the species. The results will be published in 2019.


Figure 3 Trapping diaspores in the stream Boven Slinge, Winterswijk, the Netherlands


Figure 4. The stream Boven Slinge in spring.

The actual dispersal of seeds by three native fish species

In 2016 and 2017, my research focused on the actual dispersal of seeds and potentially also vegetative plant fragments by three native fish species which feed in different habitats. This research has taken place in the lowland stream Groenlose Slinge (fig. 5). Here, I worked together with Matthijs de Vos, Michiel Schaap, Bert Klutman and John Lenssen of the Water Board Rijn en IJssel and Wilco Verberk of the Institute of Water and Wetland Research of the Radboud University. In figure 6, some of the results are shown.
In March 2019, the results were published in Frontiers in Ecology and Evolution.


Figure 5. The stream Groenlose Slinge near Borculo


Figure 6. The first results show that seeds germinated after they passed the gut of native fish. The photo above shows the germination of Poa trivialis,the photo below shows Typha latifolia grown up in the glass house.


Dispersal of bryophyte fragments (together with Philip Sollman)
Vegetative diaspores are pivotal to the ability of bryophytes to colonize new areas, but life-history traits and other factors facilitating vegetative dispersal in water bodies are largely unknown. In a paper in Journal of Vegetation Science (2019), we asked whether hydrochorous dispersal of vegetative bryophyte fragments can be predicted by specific traits in addition to discharge and local abundance of species in the species pool.


Of 144 samples collected in a navigation canal (Fig. 7), 77% contained bryophyte fragments. A total of 54,514 bryophyte fragments were determined, representing 18 species. The free-floating Riccia fluitans was the most abundant species, followed by Brachythecium rutabulum, Cratoneuron. filicinum and Platyhypnidium riparioides. In total, 55% of the variation in diaspore presence of sessile species (i.e. excluding R. fluitans) could be explained by abundance in the local vegetation, buoyancy of fragments and shoot length. Of the sessile species of which fragments were trapped, mean floating time (T50) was 5.9 days and mean shoot length 79 mm. Species that occurred in the source populations, but were not found as fragments in the water had a significantly lower buoyancy and shoot length. The number of fragments of Riccia fluitans was highest at intermediate discharges.
We conclude that abundance in the vegetation, and two simple traits (buoyancy and shoot length) are significant predictors for vegetative hydrochorous dispersal of aquatic and riparian bryophyte species; for free-floating species, discharge may be the main determining factor. As fragments of all species found are able to regenerate after being in water for several weeks, they thus may contribute to successful colonization of new favourable substrate patches along water bodies after being dispersed

Reviewing manuscripts
During the past 7 years, I was reviewer for the following peer-reviewed journals:
•    Applied Vegetation Science
•    Aquatic Botany
•    Australian Journal of Botany
•    Biological reviews
•    Biological Conservation
•    Biological Invasions
•    Ecography
•    Ecoscience
•    Encyclopedia of Inland Waters
•    Forest Ecology and Management
•    Forest Science
•    Functional Ecology
•    Global Ecology and Biogeography
•    Journal of Applied Ecology
•    Journal of Arid Environments
•    Journal of Ecology
•    Journal of Vegetation Science
•    Landscape and Urban Planning
•    NorthWest Science
•    Plant Biology
•    PLOS-one
•    River Research and Applications
•    Seed Science Research
•    Water Research
•    Wetlands

Publications can be found under the button “Publicaties” of my website.