Peer-reviewed publications


A list including citations is available viGoogle scholar
48. Navarro-Ramos, M.J., A.J. Green, R. de Vries & C.H.A. van Leeuwen (2024)
Float, fly, then sink: wetland plant seed buoyancy is lost after internal dispersal by waterbirds
Content: Many wetland plants have buoyant seeds that disperse by water movements, but also many of these seeds are ingested and transported by flying waterbirds. Interestingly, these dispersal mechanisms can also be combined to extend potential dispersal distances: first a seed floats for a while, and then it is transported even farther by a bird. Knowing this, we wondered whether seeds can continue to float again after transport by a bird, and this way disperse even over greater distances? To find out, we experimentally assessed the buoyancy capacity of 41 wetland plant species for three months before and after simulated passage through avian digestive systems. We found that most seeds sunk after digestion by waterbirds. This implies that the location where a waterbird defecates a seed is often also where the plant will have to germinate if possible. This knowlegde helps in our spatial understanding of plant community assemblies in wetlands, and the spread of invasive and endangered wetland plant species.
47. De Leeuw, J.J., J.J.J. Volwater, O.A. van Keeken, W.A.M. van Emmerik & C.H.A. van Leeuwen (2023)  
Creating wetland islands to enhance shoreline habitat for fish recruitment in a modified shallow lake
Aquatic Conservation: Marine and Freshwater Ecosystems 
Content: Soft shoreline engineering is increasingly used to combine shoreline fortification with enhancing biodiversity and biological production of land–water transitions. We studied the large-scale ecosystem restoration project “Marker Wadden”. Instead of replacing steep rip-rap shorelines with soft shorelines, multiple new wetland islands were created from local sediments in the modified Lake Markermeer (the Netherlands) – aiming to offset the declines in bird and fish populations in this Natura 2000 area. We found that both newly engineered soft shorelines and existing rip-rap shorelines contributed to habitat diversity and fish densities. However, building new additional soft shorelines as an archipelago instead of replacing existing shoreline habitats increased the total length of the land–water transitions in the lake by 16% and increased the length of soft shorelines fivefold. This novel approach contributed effectively to habitat enhancement for fish spawning and nurseries, without compromising the complementary functionality of the original, more mature, shorelines of the lake.
46. Navarro-Ramos, M.J., C.H.A. van Leeuwen, C. Olsson, J. Elmberg, J. Månsson, V. Martín-Vélez, Á. Lovas-Kiss & A.J. Green (2023)
Seed dispersal between agricultural and aquatic habitats by geese
Agriculture, Ecosystems & Environment
Content: Waterbirds are known as important dispersers of plant seeds across aquatic and terrestrial ecosystems by ingesting, transporting and egesting seeds. However, how far can birds transport seeds? Which habitat types do they connect most? And which plant species do they disperse? To answer these questions, we studied seed dispersal by greylag geese in Sweden. We combined GPS-tracking of geese with simultaneous collections of faecal samples in the agricultural habitats that the birds visited. Geese transported 41 plant species of 19 different families, which included 9 agricultural weeds and one alien species. Most seeds were exchanged among lakes, pastures and barley fields: these were the habitats that were most connected by direct flights, and also had the highest plant species richness and seed abundance in the collected faecal samples. Agricultural fields closest to aquatic habitats were visited most.
45. Van Leeuwen, C.H.A, J.J. de Leeuw, J.J.J. Volwater, O.A. van Keeken, H. Jin, A.M. Drost, D. Waasdorp, E. Reichman, L. Ursem & E.S. Bakker (2023)
Creating new littoral zones in a shallow lake to forward-restore an aquatic food web
Science of the Total Environment
Content: Current rates of habitat loss require science-based predictions on how to restore or newly create lost habitat types. Littoral zones of lakes are key habitats for aquatic food web functioning, but are often replaced by unnatural steep shorelines. We assessed how a degraded aquatic food web responded to the new creation of a 1,000 ha archipelago in a 70,000 ha shallow lake. New littoral zones stimulated vegetation, zooplankton, macro-invertebrates and young-of-the-year fish. We conclude that creating new littoral zones in heavily modified systems can stimulate multiple trophic levels in aquatic food webs simultaneously, which provides proof-of-principle for the new “forward-looking restoration” approach.
44. Lovas-Kiss, Á., Navarro-Ramos, M. J., Vincze, O., Löki, V., Urgyán, R., Pallér-Kapusi, F., van Leeuwen, C. H. A., Green, A. J., & Lukács, B. A. (2023).
Traits for transport: Alien wetland plants gain an advantage during endozoochorous seed dispersal by waterfowl.
Freshwater Biology
Content: We address the potential of alien plant seeds to disperse via ingestion, transport and egestion in waterfowl (endozoochory). Based on their general rapid expansions, we expected alien plant species to have several advantages for endozoochory compared to native plant species. We compared the endozoochorous dispersal ability of six pairs of congeneric alien and native wetland plant species in a feeding experiment with mallards (Anas platyrhynchos). We found seeds of alien plant species to have traits that correlate with successful endozoochory. This may provide alien species with a competitive advantage over native plant species by ensuring higher endozoochory rates in new environments, potentially enabling their rapid expansions.
43. Van Leeuwen, C.H.A., de Leeuw, J.J., van Keeken, O.A. et al. (2023)
Multispecies fish tracking across newly created shallow and deep habitats in a forward-restored lake
Content: Human impact increasingly leads to loss of natural heterogeneity and its associated rich fish communities. To reverse this trend, we need guidelines on how to effectively restore or recreate habitats for multiple fish species. We assessed how omnivorous and piscivorous fish species used newly constructed littoral zones and a deep sand excavation in the degraded shallow lake Markermeer. The new littoral and deep habitats in the uniform lake attracted omnivorous and piscivorous fish species within four years. Both feeding guilds used the littoral zones for reproduction and nursery, and notably piscivorous fish became residents year-round. Notably piscivorous pikeperch was using the shallow zones all year round, and was strongly attracted to the 30m-deep sand excavations that were created during construction of the islands. This knowlegde offers new insights in how fish communities in degraded aquatic ecosystems can be stimulated by the creation of new habitat features.
42. Jin, H., D.B. Van de Waal, C.H.A. van Leeuwen, L.P.M. Lamers, S.A.J. Declerck, A.L. Amorim, and E.S. Bakker (2023)
Restoring gradual land-water transitions in a shallow lake improved phytoplankton quantity and quality with cascading effects on zooplankton production
Content: We investigated whether enhancing habitat complexity and heterogeneity by restoring land-water transition areas in human-modified lake systems is a suitable method to restore degrading aquatic food webs. We found that newly created land-water transition areas for a large-scale lake restoration project called "Marker Wadden" in the Netherlands increased light and nutrient availabilities under water, which bottom-up stimulated lower trophic levels of the aquatic food web (phytoplankton, zooplankton). This in turn is expected to stimulate higher trophic levels (fish, birds) in the aquatic food web.
41. A.J. Green, Á. Lovas-Kiss, C. Reynolds, E. Sebastián-González, G.G. Silva, C.H.A. van Leeuwen, D.M. Wilkinson (2023)
Dispersal of aquatic and terrestrial organisms by waterbirds: A review of current knowledge and future priorities
Freshwater Biology  pdf
Content: We review progress in our understanding of the importance of waterbirds as dispersal vectors of other organisms, and identify priorities for further research.
40. C.H.A. van Leeuwen, M.B. Soons, L.G.V.T.I. Vandionant, A.J. Green, E.S. Bakker (2023)
Seed dispersal by waterbirds: a mechanistic understanding by simulating avian digestion
Ecography (open access)
Content: Waterbirds disperse plant species via ingestion and egestion of seeds (endozoochory). However, our understanding about the regulating effects of seed traits, underlying mechanisms and possible (co)evolutionary processes is limited by our traditional reli-ance on data from feeding experiments with living waterbirds. Here, we overcome these limitations by developing and applying a new bioassay that realistically simu-lates digestive processes for Anseriformes waterbirds. We test three hypotheses: 1) seed survival and germination are most affected by mechanical digestion in the waterbird gizzard; 2) seed size, hardness, imbibition and shape regulate seed survival; and 3) plants growing in aquatic habitats benefit most from endozoochory by waterbirds. Experiments with 28 200 seeds of 48 plant species demonstrated species-specific seed survival that was entirely determined by digestion in the avian gizzard. Intestinal diges-tion did not affect seed survival but affected seed establishment (germinability and germination time) for 21% of the species. Large, hard seeds survived the simulations the best, in contrast to generally higher seed survival for smaller seeds during in vivo experiments. This mechanistically explains that small seeds escape digestive processes rather than being inherently more resistant (the ‘escape mechanism’), while large seeds are retained until fully digested or regurgitated (the ‘resistance and regurgitation mechanism’). Plants growing in wetter habitats had similar seed survival, but digestive processes stimulated their germinability and accelerated their germination more than for terrestrial plants. This indicates a relative advantage of endozoochory for plant species growing in wet habitats, possibly reflecting a co-evolutionary response related to dormancy breaking by gut passage. Simulating seed gut passage using a bioassay allowed establishing mechanisms and identifying relevant seed traits involved in seed dispersal by waterbirds. This information enhances our understanding of how animal species shape plant species distributions, which is extremely relevant now that current anthropogenic pressures already severely impact plant dispersal capacities.
39. C.H.A. van Leeuwen, N. Villar, I. Mendoza Sagrera, A.J. Green, E.S. Bakker, M.B. Soons, M.Galetti, P.A. Jansen, B.A. Nolet, L. Santamaría (2022)
A Seed Dispersal Effectiveness framework across the mutualism–antagonism continuum
Content: Many angiosperms rely on vertebrates for seed dispersal via gut passage, an interaction that has been traditionally classified as a mutualism. The seed dispersal effectiveness (SDE) framework provides a mechanistic approach to evaluate evolutionary and ecological characteristics of animal-mediated seed dispersal, by synthesising the quantity and the quality of the dispersal that a plant species receives from each of its animal dispersers. However, the application of the SDE framework has been largely restricted to plant–frugivore interactions, whereas animal-mediated seed dispersal results from plant–disperser interactions that cover a continuum from pure mutualisms to antagonisms. This biases ecological and evolutionary knowledge on plant–disperser interactions. Here, we propose an extended SDE framework (‘eSDE') that allows comparing plant–disperser interactions in the full mutualism–antagonism continuum ranging from pure mutualisms (frugivores) to conditional mutualisms (scatter-hoarding granivores and folivores) and antagonisms (pure granivores).
38. H. Jin, C.H.A. van Leeuwen, R.J.M. Temmink, E.S. Bakker (2022)
Impacts of shelter on the relative dominance of primary producers and trophic transfer efficiency in aquatic food webs: Implications for shallow lake restoration
Freshwater Biology
Content: We studied the impact of wind on aquatic primary producers and transfer efficiency of this energy to higher trophic levels. We hypothesised that reducing wind-induced turbulence would lead to higher trophic production in shallow lakes. We tested our hypothesis by creating mesocosms in the shallow waters of the restoration project "Marker Wadden" in lake Markermeer in the Netherlands, and studying the effects of this artifically created shelter on aquatic food webs. Creation of shelted facilitated submerged macrophytes, increased Gastropoda densities and increased trophic transfer efficiency between phytoplankton and zooplankton. Creating shelter in shallow lake ecosystems suffering from strong wind-effects can have positive effects on food availability for higher trophic levels, such as fish and water birds.

37. M.J. Navarro‐Ramos, A.J. Green, A. Lovas‐Kiss, J. Roman, K. Brides, and C.H.A. van Leeuwen (2022)
A predatory waterbird as a vector of plant seeds and aquatic invertebrates
Freshwater Biology
Content: We studied the potential of predatory waterbirds to disperse aquatic organisms via secondary dispersal, using the grey heron Ardea cinerea in Europe as an example species. Grey herons regurgitate undigestible remains of their prey in pellets. Examinations of these pellets collected throughout northwestern Europe showed that a wide variety of aquatic invertebrates and plant seed is dispersed by herons in these pellets. Plant taxa were dominated by Caryophyllaceae, Cyperaceae, Juncaceae, and Poaceae, with 24 species from the littoral zone (Ellenberg moisture values of 7–12) and 21 terrestrial species (Ellenberg moisture values of 4–6). Intact invertebrate propagules were found in 30% of the pellets, dominated by Cladocera and Bryozoa. Our findings showcase the potential of predatory waterbirds as vectors of plants and invertebrates, and how they may facilitate connectivity between freshwater and terrestrial habitats.

36. H. Jin, C.H.A. van Leeuwen, D.B. van de Waal, E.S. Bakker (2022)
Impacts of sediment resuspension on phytoplankton biomass production and trophic transfer: Implications for shallow lake restoration
Science of The Total Environment
Content: We quantified the effects of reducing wind-induced resuspension in shallow lakes as a form of shallow lake restoration. We varied resuspension levels in an indoor microcosm experiment, and monitored the effects on phytoplankton, benthic algae and zooplankton at different temperatures. Reducing resuspension decreased nutrient concentrations and phytoplankton biomass build-up, but increased light availability, benthic algae biomass and zooplankton. This suggests that creating sheltered areas in shallow lakes suffering from wind effects can be effective in increasing trophic transfer of phytoplankton to zooplankton, and can stimulate secondary production and higher trophic levels. We link these results to Marker Wadden, a large-scale restoration project in Lake Markermeer in the Netherlands.

35. R.J.M. Temmink, M. van den Akker, C.H.A. van Leeuwen, Y. Thöle, H. Olff, V.C. Reijers, S.T.J. Weideveld, B.J.M. Robroek, L.P.M. Lamers, E.S. Bakker (2022)
Herbivore exclusion and active planting stimulate reed marsh development on a newly constructed archipelago,
Ecological Engineering    pdf
Content: We conclude that the establishment of reed marshes can strongly benefit from excluding herbivores and the introduction of reed, and that otherwise different vegetation types may establish and may establish more slowly. This is especially relevant when restoring or creating new wetland ecosystems, for which vegetation development is often a crucial first step. Our work illustrates how active management of vegetation development has the potential to benefit novel ecosystems.

34. C.H.A. van Leeuwen, R.J.M. Temmink, H. Jin, Y. Kahlert, B.J.M. Robroek, M.P. Berg, L.P.M. Lamers, M. van den Akker, R. Posthoorn, A. Boosten, H. Olff, E.S. Bakker. (2021)              
Enhancing ecological integrity while preserving ecosystem services: constructing soft-sediment islands in a shallow lake               
Ecological Solutions and Evidence    pdf              
Content: Classical restoration of  degrading freshwater ecosystems can lead to societal opposition, if returning to a former ecosystem state affects previously acquired ecosystem services. Innovative nature-based solutions are therefore needed that enhance natural values in ecosystems, without affecting existing services. We present the first results of a large-scale project - called the "Marker Wadden" - which aims to increase the ecological integrity of a human-modified freshwater lake while maintaining its services to humans. Within 4 years, the Marker Wadden project shows how forward-looking sustainable development of lake ecosystems using a rewilding approach can enhance natural processes.

33. Martín Vélez, V; Van Leeuwen, C.H.A.; Sánchez, M.; Hortas, F.; Shamoun-Baranes, J.; Thaxter, C.; Lens, L.; Camphuysen, C. & A. J. Green (2021)              
Spatial patterns of weed dispersal by wintering gulls within and beyond an agricultural landscape
Journal of Ecology  
Content: Gulls can disperse weed plants over long distances across a mosaic of habitats. This implies exchange of weed plant species between human‐dominated and natural areas by waterbirds as dispersal vectors. This spatial study highlights the importance of non‐frugivorous birds for long‐distance plant dispersal, which is generally an overlooked mechanism in studies aiming to predict and manage expansion of weed plants.

32. Mulder, A.J.E., van Aalderen, R. & C.H.A. van Leeuwen (2021)
Tracking temperate fish reveals their relevance for plant seed dispersal
Functional Ecology  pdf               
Content: We calculated the first realistic dispersal kernels for plant seeds dispersed by temperate fish species, by combining acoustic tracking with laboratory experiments. This novel approach increases our understanding of plant-animal interactions in an understudied system. We draw conclusions about maximum dispersal distances, intraspecific variation, seasonality and effects of anthropogenic barriers.

31. Petruzzella, A., T.A. da S. S. R. Rodrigues, C.H.A. van Leeuwen, F. de Assis Esteves, M. Paulo Figueiredo-Barros & E.S. Bakker (2020)               
Species identity and diversity effects on invasion resistance of tropical freshwater plant communities
Scientific Reports 10, 5626 pdf
Content: We investigated how native plant community presence and diversity - and the presence of native phylogenetically closely related species to invading plant species - affect the establishment success of invading tropical freshwater submerged plant species. The presence of a native plant community suppressed the growth of the invading species (Hydrilla verticillata), but did not prevent its colonisation. Invader growth was negatively affected by native plant productivity, but independent of native species richness and phylogenetic relatedness to the invader. This illustrates that resistance provided by tropical freshwater submerged plant communities to invasive species contrasts to resistance described for other ecosystem types.

30. Zhang, P., van Leeuwen, C.H.A., Bogers, D. Poelman, M. Xu, J. & E.S. Bakker (2020)
Ectothermic omnivores increase herbivory in response to rising temperatures 
Oikos     doi: 10.1111/oik.07082 pdf
 Content: Ectothermic herbivores and carnivores generally ingest more food with rising temperature as their metabolic rates increase with rising temperature. We hypothesized that rising temperature would increase herbivory of ectothermic omnivores, and confirmed this hypothesis in a freshwater model system with the pond snail Lymnaea stagnalis. A literature survey furthermore suggested that aquatic ectothermic omnivores might commonly increase herbivory with rising temperatureWe conclude that future global warming will most likely alter food webs by increasing the top–down control of aquatic herbivores and omnivores on primary producers.

29. Petruzzella, A., van Leeuwen, C.H.A., van Donk, E. & E.S. Bakker (2020)
Direct and indirect effects of native plants and herbivores on biotic resistance to alien aquatic plant invasions
Journal of Ecology doi10.1111/1365-2745.13380 pdf
Content:  Biotic resistance to alien plant invasions is mainly determined by ecological interactions in two layers of the food web: competition with native plant species and herbivory by native herbivores. While the direct effect of native plants on alien plant performance via competition has been well documented across ecosystems, less is known about the direct and indirect effects of herbivores in providing biotic resistance. We found experimental evidence for biotic resistance through competition by native plant species. However, we show that in freshwater ecosystems herbivores can indirectly facilitate invasions by promoting invader growth through selective feeding on filamentous algae. This illustrates the importance of indirect interactions to understand biotic resistance in natural ecosystems.            

28. Van Leeuwen, C.H.A., Tella, J. L. & Green, A. J. (2020)
Editorial: Animal-Mediated Dispersal in Understudied Systems.  
Frontiers in Ecology and Evolution Ebook available here
Content: Animals disperse smaller organisms by ingesting, transporting and egesting propagules such as plant seeds, fruits, small invertebrates and algae (internal transport), or by carrying propagules attached to their exterior (external transport). Animal-mediated dispersal is generally well studied, but most previous work focused on only a handful of species networks. We initiated a Research Topic in which we gathered studies on animal-mediated dispersal that involved poorly studied and previously overlooked propagules and disperser animals. We hope this collection of 14 new papers will broaden our knowledge beyond the currently most-studied systems, and will inspire future work on contrasts and similarities across study systems.

27. Zhang P., Kuramae A., van Leeuwen C.H.A., Velthuis M., van Donk E., Xu J. and Bakker E.S. (2020)
Interactive effects of rising temperature and nutrient enrichment on aquatic plant growth, stoichiometry, and palatability
Frontiers in Plant Science 11:58. doi: 10.3389/fpls.2020.00058 pdf
Content: Temperature rise and eutrophication are global environmental changes that can affect aquatic plants and their palatability to herbivores. However, these factors often change simultaneoulsy. We studied how temperature rise and eutrophication interactively affect aquatic plants. We tested the hypotheses that (1) plant growth rates increase faster with rising temperature in nutrient-rich than nutrient-poor sediments; (2) plant carbon to nutrient ratios respond differently to rising temperatures at contrasting nutrient conditions of the sediment; (3) external nutrient loading to the water column limits the growth of plants and decreases plant C:nutrient ratios; and that (4) changes in plant stoichiometry affect plant palatability.

26. Van Leeuwen, C.H.A., Tella, J. L. & Green, A. J. (2020)
Editorial: Animal-Mediated Dispersal in Understudied Systems. 
Frontiers in Ecology and Evolution doi: 10.3389/fevo.2019.00508 pdf
Content: Editorial publication outlining seven key lessons we can learn from the 14 new publications we published in our Special Issue on "Animal-mediated dispersal in understudied systems".

25. Martín-Vélez, V., Mohring, B., van Leeuwen, C. H. A., Shamoun-Baranes, J., Thaxter, C. B., Baert, J. M., Camphuysen, C. J. & Green, A. J. (2019)
Functional connectivity network between terrestrial and aquatic habitats by a generalist waterbird, and implications for biovectoring.
Science of the Total Environment 135886. pdf
Content: The functional connectivity network of gulls wintering in Southern Spain was found to functionally link seven habitat types. Dominant habitat types were ricefields and rubbish dumps (landfills). High connectivity of terrestrial landfills with wetlands suggests that waterbirds can transport nutrients, contaminants and antibiotic resistance to and from protected wetland habitats.

24. J.P van Zuidam*, C.H.A. van Leeuwen*, E.S. Bakker, J.T.A. Verhoeven, S. IJff, E.T.H.M. Peeters, B.G. van Zuidam, M.B. Soons (2019) *shared first authors
Plant functional diversity and nutrient availability can improve restoration of floating fens via facilitation, complementarity and selection effects

Journal of Applied Ecology pdf
Content: Peat‐forming wetlands, and particularly floating fens forming the initial stages of these ecosystems, are globally declining due to excavation, dehydration and eutrophication. Restoration of these valuable ecosystems typically involves re‐establishment of early‐successional open‐water stages with oligotrophic conditions that are characteristic for these systems. However, restoration success is notoriously limited. We experimentally tested how (1) increasing functional diversity of introduced species and (2) nutrient availability would possibly stimulate resotration success, using 36 artificial outdoor ponds for 2 years. We found that restoration of floating fen communities (1) can be stimulated by introducing a high functional diversity of plant species, including fast‐growing clonal species, clonal stress‐tolerators and interstitials, which facilitate each other, (2) is dependent on the presence of clonal stress‐tolerators such as Calla palustris, Comarum palustre and Menyanthes trifoliata for expansion onto the open water, (3) can start under a wide range of water nutrient levels, including eutrophic conditions.

23. Zhang, P., B.M. Grutters, C.H.A. van Leeuwen, J. Xu, A Petruzzella, R.F. van den Berg, E.S. Bakker (2018)
Effects of rising temperature on the growth, stoichiometry and palatability of aquatic plants
Frontiers in Plant Science pdf
Content: We experimentally investigated how rising water temperatures - as an important component of global changes - may affect plant chemical traits and plant palatability in freshwater ecosystems. If warming water would increase plant palatability to herbivores, this could subsequently increase top-down control of aquatic vegetation in the future. We found that warming generally stimulated the growth of the investigated aquatic plant species, but also that any changes in plant traits and palatability were highly species-specific. This implies that species identity is an important factor to take into account when predicting how global change may affect aquatic vegetation in the future.

22. Zhang, P, R.F. van den Berg, C.H.A. van Leeuwen, B.A. Blonk, E.S. Bakker, (2018)
Aquatic omnivores shift their trophic position towards increased plant consumption as plant stoichiometry becomes more similar to their body stoichiometry

PLoS ONE  pdf
Content: Eutrophication in aquatic ecosystems increases plant nutrient concentrations. We experimentally showed that aquatic omivores shift to a more plant-based diet in more eutrophied aquatic systems, because plants become relatively more attractive food sources. Because most aquatic consumers are omnivores, increased nutrient loadings into aquatic systems may increase top-down control on aquatic plants.

21. C.H.A. van Leeuwen (2018)
Internal and external dispersal of plants by animals: an aquatic perspective on alien interference
Frontiers in Plant Sciences 9:153 pdf
Content: Many alien plants use animal vectors for dispersal of their diaspores (zoochory). If these alien plants interact with native disperser animals, this can interfere with animal-mediated dispersal of native diaspores. Interference by alien species is known for frugivorous animals dispersing fruits of terrestrial plants by ingestion, transport and egestion (endozoochory). However, little attention has been paid to possible interference of alien plants with dispersal of diaspores via external attachment (ectozoochory, epizoochory or exozoochory), interference in aquatic ecosystems, or positive effects of alien species on dispersal of native plants. In this literature study I address the following hypotheses: (1) alien plants may interfere with both internal and external animal-mediated dispersal of native diaspores; (2) interference also occurs in aquatic ecosystems; (3) interference of alien plants can have both negative and positive effects on native plants. Testing these hypotheses using the literature reveals many possibilities for future research and emphasizes the importance of understanding the effects of alien plant species on animal-mediated dispersal in the light of conservation.
20. Van Leeuwen, C.H.A. and S.E. Jamieson (2018)
Strong pair bonds and high site fidelity in a subarctic-breeding migratory shorebird
The Wilson Journal of Ornithology 130(1):140-151 pdf 
Content: We investigated mate and site fidelity of the migratory shorebird Pacific Dunlin (Calidris alpina pacifica) breeding at the subarctic Yukon-Kuskokwim Delta, Alaska, USA. We found subarctic-breeding Dunlin to strongly prefer previous breeding locations and previous mates when these were available in consecutive breeding attempts. However, if sites or mates were unavailable for breeding, their behavior prioritized early nest initiation and fast renesting over mate and site fidelity. This study illustrates the high importance of timing for migratory birds nesting in the short subarctic summer.
19. Petruzzella, A., Manschot, J., Van Leeuwen, C.H.A., Grutters, B.M. and E.S. Bakker (2018)
Mechanisms of invasion resistance of aquatic plant communities
Frontiers in Plant Sciences 9:134 pdf
Content: A greenhouse experiment with aquatic plants revealed that the presence of native vegetation decreased the establishment success of an alien aquatic plant species. The strength of this biotic resistance increased with increasing species richness of the native community. Native biomass of mixed communities overyielded, which further lowered the establishment success of the invader. Strongest biotic resistance was caused by the two native plant species that were functionally most similar to the invader.
18. Van Leeuwen, C.H.A., K. Dalen, J. Museth, C. Junge and L.A. Vøllestad (2018)
Habitat fragmentation has interactive effects on the population genetic diversity and individual behaviour of a freshwater salmonid fish
River Research and Applications 34(1):60-68 pdf
Content: We investigated how habitat fragmentation interacted with population genetic diversity and individual behaviour of European grayling (Thymallus thymallus) in a large river systems. Combining genotyping and radio-tracking of adult fish indicated that (1) upstream sub-populations in fragmented rivers show less genetic variation, which makes it less likely for them to adapt to environmental changes; (2) fish with distinct genotypes in the same habitat can differ in their behaviour; (3) spawning site selection (natal philopatry) can differ between fish of the same species living in different habitats (river or lake-tributary systems). Habitat loss and river fragmentation may differently affect individual fish of the same species, if they live in different types or sections of habitat.
17. Van Leeuwen, C.H.A., Á. Lovas-Kiss, M. Ovegård and A.J. Green (2017)
Great cormorants reveal overlooked secondary dispersal of plants and invertebrates by piscivorous waterbirds
Biology Letters 13(10): 20170406 pdf
Content: Birds and fishes frequently disperse plants by ingesting plant seeds, then moving before egesting them, so helping to maintain plant biodiversity. Since birds move more than fish, Darwin first proposed that fish-eating birds may be important for dispersing seeds that were inside the fish when they swallowed them. We studied this idea in great cormorants, widespread fish-eating birds that egest indigestible items in pellets. We found these pellets to contain a wide diversity of aquatic and terrestrial plant seeds, plus aquatic invertebrates. The species that were dispersed depended on what fish species were eaten. This study is the first to quantify the role of fish-eating birds in dispersing plants and invertebrates.
16. Van Leeuwen, C.H.A., T. Dokk, T.O. Haugen, P.M. Kiffney and J. Museth (2017)
Small larvae in large rivers: observations on downstream movement of European grayling Thymallus thymallus during early life stages
Journal of Fish Biology 90(6): 2412-2424 pdf
Content: We investigated behaviour of early life stages of the salmonid European grayling Thymallus thymallus in large river systems by trapping of larvae moving downstream and electrofishing surveys. Larvae moved downstream predominantly during night, close to the substrate, and few young-of-the-year still resided close to the spawning areas in autumn. These observations advocate that there may be a deliberate, active component to downstream movement of European grayling during early life stages. This implies that human alterations of flow regimes and the construction of reservoirs for hydropower interfere with active movement behaviour of fish during critical early life stages. 
15. Gilioli G., Schrader G., Carlsson N., van Donk E., Van Leeuwen C.H.A., Martín P.R., Pasquali S., Vila M. and S. Vos (2017)
Environmental risk assessment for invasive alien species: A case study of apple snails afffecting ecosystem services in Europe 
Environmental Impact Assessment Review 65: 1-11 pdf
Content: We present a case study that illustrates how quantitative estimates of environmental risk assessment impacts can be used by decision makers and managers that have to balance the costs of control efforts against environmental and economic impacts of invasive species. The invasive apple snails Pomacea canaliculata and Pomacea maculata are used to demonstrate the application of an innovative procedure ssessing the potential impact of these species on shallow freshwater ecosystems with aquatic macrophytes in Europe. 
14. Van Leeuwen, C.H.A., J. Museth, O.T. Sandlund, T. Qvenild and L.A. Vøllestad. (2016) 
Mismatch between fishway operation and timing of fish movements: a risk for cascading effects in partial migration systems 

Ecology and Evolution 6(8):2414-2425 pdf

Content: Fishways with restricted seasonal operation times were found to affect upstream spawning migrations of both spring and autumn spawning salmonid fish. We discuss possible effects of late opening and early closing of fish passages in a theoretical framework, in which we propose that movement restrictions of migratory individuals in partially migratory populations can also indirectly affect conditions for resident fish in the same river system.

13. Van Leeuwen, C.H.A., R. BeukeboomB.A. Nolet, E.S. Bakker and B.J.A. Pollux (2016)
Locomotion during digestion changes current estimates of seed dispersal kernels by fish
Functional Ecology 30:215-225 pdf
Content: Physical activity during animal locomotion affects how their digestive system processes food, which has implications for their role as seed dispersers. We found that physically active fish retained ingested seeds longer than inactive fish, implying that modelling dispersal kernels using parameters from inactive fish underestimates potential dispersal distances of plants by endozoochory in aquatic systems. 
12. Noback, M.L., E. Samo, C.H.A. van Leeuwen, N. Lynnerup, and K. Harvati (2016)
Paranasal sinuses: A problematic proxy for climate adaptation in Neanderthals
Journal of Human Evolution 97: 176-179 pdf
Content: We contribute to an online discussion on whether paranasal sinuse volume can be used as a proxy for climate adaptation in humans and Neanderthals. According to our data past inferences on this relation are problematic.
11. Kleyheeg, E. and C.H.A. van Leeuwen (2015)
Regurgitation by waterfowl: an overlooked mechanism for long-distance dispersal of wetland plant seeds
Aquatic Botany 127:1-5 pdf
Content: Seed regurgitation by waterbirds is an overlooked dispersal mechanism in wetlands. We found that regurgitation by waterbids can follow overfeeding or the ingestion of large indigestible seeds. As plant seeds are more likely to survive regurgitation than entire gut passage, regurgitation may make a suitable dispersal pathway for seeds that are unable to resist digestion during endozoochory.  
10. Garcia-Álvarez, A., C.H.A. van Leeuwen, C.J. Luque, A. Hussner, A. Vélez-Martin, A. Pérez-Vázquez, A.J. Green, E.M. Castellanos (2015)

Internal transport of alien and native plants by geese and ducks - an experimental study
Freshwater Biology 60(7): 1316-1329 pdf
Content: Experiments on the transport of plant seeds by waterbirds revealed that: i) smaller ducks differ from larger geese in their role as dispersal vectors ii) invasive water primrose Ludwigia grandiflora has a greater dispersal potential than invasive cordgrass Spartina densiflora, which is consistent with its faster range expansion across Europe, and iii) maximum retention times of wetland seeds have been underestimated in previous experimental studies that lasted only 1–2 days, as intact seeds were retrieved from faeces for up to 4 days after ingestion. More attention should be paid to the role of waterbirds as vectors of alien plants and to the role of migratory geese as vectors of plants in general.  

9. Kleyheeg, E., C.H.A. van Leeuwen, M.A. Morison, B.A. Nolet and M.B. Soons (2014)
Bird-mediated seed dispersal: reduced digestive efficiency in active birds modulates dispersal capacity of plant seeds
Oikos 124(7): 899-907 pdf
Content: Seed retrieval patterns of nine wetland plants were found to differ between resting and physically active mallards (Anas platyrhynchos). Physical activity increased the retrieval of intact seeds and modestly accelerated gut passage of seeds, however, in a plant species-specific way. Interactions between the digestion resilience of a particular seed species and the physical activity of an actively moving vector organism should be taken into account when constructing zoochoric dispersal kernels.
8. Van Leeuwen, C.H.A., J.M. Sarneel, J. van Paassen, W. Rip and E.S. Bakker (2014) 

Hydrology, shore morphology and species traits affect seed dispersal, germination and community assembly in riparian plant communities.

Journal of Ecology 102: 998-1007 pdf

Content: Seed dispersal and germination of plants on the shores of wetlands is influenced by water level fluctuations, shore morphology and seed characteristics. Active water level management and shore restoration can contribute to the creation of rich riparian plant communities.


7. Van Leeuwen, C.H.A., N. Huig, G. van der Velde, T.A. van Alen, C.A.M. Wagemaker, C.D.H. Sherman, M. Klaassen and J. Figuerola (2013)

How did this snail get here? Multiple dispersal vectors inferred for an aquatic invasive species.

Freshwater Biology 58(1): 88-99 pdf

Content: Microsatellite analyses reveal how invasive aquatic snails (Physa acuta) can colonize isolated freshwater ponds in Doñana National Park (Spain) by using a multitude of passive dispersal vectors: water currents, waterbirds and large mammals.


6. Van Leeuwen, C.H.A., G. van der Velde, J.M. van Groenendael and M. Klaassen (2012)

Gut travellers: internal dispersal of aquatic organisms by waterfowl.

Journal of Biogeography 39(11): 2031-2040 pdf    supp1   supp2   supp3

Content: This is the first quantitative meta-analysis on internal transport of aquatic invertebrates and wetland plant seeds by waterbirds. Analysis of over 80 publications (which can be found in supplementary 1) indicates the state of the art on bird-mediated dispersal, and is used to present the first calculations on the quantitative and qualitative importance of endozoochory as a long distance dispersal mechanism.

5. Van Leeuwen, C.H.A. and G. van der Velde (2012)

Prerequisites for flying snails: external transport potential of aquatic snails by waterbirds.

Freshwater Science 31(3): 963-972 pdf

Content: This study experimentally addresses dispersal of snails on the outside of birds, known as ectozoochory. A large selection of aquatic snail species is highly tolerant to desiccation, will attach readily to the exterior of waterbirds, and can stay attached for over 8 hours in drying mud. Aquatic snails appear to have all the necessary prerequisites for successful zoochory by birds or other large animals.

4. Van Leeuwen, C.H.A., M.L. Tollenaar, and M. Klaassen (2012)

Vector activity and propagule size affect dispersal potential by vertebrates.

Oecologia 170(1): 101-109 pdf

Content: In this paper we describe how physical activity of mallards (Anas platyrhynchos), in the form of swimming, alters their digestive physiology. This has implications for the construction of seed dispersal kernels by zoochory, which have to date always been based on seed release patterns obtained from experiments with resting animals. We show for the first time that modelling dispersal kernels to predict seed dispersal distances by zoochory should incorporate potential digestive changes induced by the physical movement of animal vectors.

3. Van Leeuwen, C.H.A., G. Van der Velde, B. Van Lith, and M. Klaassen (2012) 

Experimental quantification of long distance dispersal potential of aquatic snails in the gut of migratory birds.

PLoS ONE 7:e32292 pdf

Content: This publication shows how aquatic snails can survive digestion of waterbirds. In a feeding experiment, snails were retrieved over five hours after ingestion, indicating for the first time that long distance endozoochory of aquatic snails is possible.

2. Dietz M.W., B. Spaans, A. Dekinga, M. Klaassen, H. Korthals, C.H.A. van Leeuwen, and T. Piersma (2010) 

Do red knots (Calidris canutus islandica) routinely skip Iceland during southward migration?

Condor 112(1): 48-55 pdf

Content: Stable isotope analyses of red knots (Calidris canutus islandica) reveal that these birds do not always use all available stopover sites on migration, but that direct migration from Greenland to Western-Europe occurs without a stopover in Iceland, even for juveniles.

1. Klaassen, R.H.G., B.A. Nolet, and C.H.A. van Leeuwen (2007)

Prior knowledge about spatial pattern affects patch assessment rather than movement between patches in tactile-feeding mallard.

Journal of Animal Ecology 76(1): 20-29 pdf

Content: This experiment with mallards (Anas platyrhynchos) reveals that birds searching for cryptic food items can make use spatial patterns to optimize their food intake over time.

Non-peer reviewed articles and reports

  • De Leeuw, J.J., Volwater, J.J.J. van Keeken, O.A., Elings, J. & C.H.A. van Leeuwen (2022) Paai- en opgroeigebieden voor vis in en rond Marker Wadden, Wageningen Marine Research, report 2022
  • De Leeuw, J.J., Volwater, J.J.J. van Keeken, O.A. & C.H.A. van Leeuwen (2022) Broedkamer Marker Wadden Visionair: het vakblad van sportvisserij Nederland 16 (63), 38-41
  • C.H.A. van Leeuwen (2022), Vissen als verspreiders van plantenzaden, RAVON magazine
  • C.H.A. van Leeuwen, R. Temmink, H. Jin, Y. Kahlert, B. Robroek, M. Berg, …. ES Bakker (2022) Ecosysteemherstel door vijf jaar oude Marker Wadden, De Levende Natuur 123 (1)
  • R. Temmink & C.H.A. van Leeuwen, Wat er leeft, 2022, De Levende Natuur 123 (1)