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The impact of seed-dispersal by animals on plant distributions: an experimental and modelling approach

Periodic Reporting for period 1 - DIGEST (The impact of seed-dispersal by animals on plant distributions: an experimental and modelling approach)

Reporting period: 2017-05-01 to 2019-04-30

Many plant species produce seeds that are ingested, transported and egested by animals. The importance of this dispersal mechanism is today best known for terrestrial plant species producing fleshy-fruits around their seeds to attract animals. However, animals also massively ingest seeds that lack fleshy components in wetland ecosystems, suggesting this dispersal mechanism to also impact wetland biodiversity. Current global pressures on wetlands urge a better understanding of the dispersal mechanisms regulating biodiversity in such “islands in a sea of land”. This project increased our mechanistic understanding of animal-mediated dispersal in wetland ecosystems, and so far concludes that (I) animal-mediated dispersal may be equally important in terrestrial and aquatic habitats; (II) the importance of waterbirds for plant seed dispersal can be predicted based on seed traits such as size and hardness; (III) piscivorous birds secondarily disperse wetland plant seeds first ingested by fish; (IV) alien plant species may also be further dispersed by animals. This project improved our mechanistic understanding of endozoochory, fused terrestrial and aquatic ecology, exchanged knowledge between academia and industry, and informed on an important ecological process in a globally changing world.
Over the two-year study period I prepared an interdisciplinary meta-analysis to advance the field of animal-mediated plant dispersal (WP1 - publication in preparation), developed (WP2) and applied (WP3) artificial digestion protocols to generate species-specific information on the potential of plants to use animals for their seed dispersal, and applied biogeographical modelling to increase our understanding of plant-animal interactions on plant distributions (WP4).

WP1: The main task of this WP was to collect and analyze literature (Milestone 1.1) which I used to organize interdisciplinary discussions with terrestrial and aquatic international authorities on animal-mediated plant dispersal. One manuscript linking terrestrial and aquatic ecology is published and one in preparation (Deliverable 1.1).
The first manuscript has been published in Frontiers in Plant Sciences and forms a bridge between terrestrial and aquatic animal-mediated plant dispersal, notably in relation to dispersal of alien species. The second manuscript is based on an international workshop is in preparation and will further bridge terrestrial and aquatic disciplines on animal-mediated plant dispersal. I co-edited a special issue in Frontiers in Ecology and Evolution on zoochory (https://www.frontiersin.org/research-topics/7222/animal-mediated-dispersal-in-understudied-systems).

WP2: The major milestone of this WP (Milestone 2.1) was the completion of artificial digestion protocols. With two students, an assistant and a secondment at the dairy company FrieslandCampina we developed artificial digestion protocols for waterbirds and verified its accuracy with in vivo data. One manuscript on the method (Deliverable 2.1) and one using the method are in preparation.

WP3: Seeds were obtained (Milestone 3.1) and the digestion protocols were applied to seeds of a wide range of plant species (Milestone 3.2) the seed were germinated under controlled conditions (Milestone 3.3) and the data will be submitted to the LEDA trait database (Deliverable 3.1) upon publication of the manuscript (in preparation). A wide range of seed traits were measured and compared among the plant species, and currently data is analyzed to match the seed traits to their ability to survive artificial digestion. Several seed traits (hardness, size, shape) were identified as important for seed survival. These results have been presented at conferences (Pan Eureopean Duck Symposium, Netherlands Annual Ecological Meeting) and the seed dispersal symposium organized at the host institute in April 2019.

WP4: Plant range expansions and animal movement data for modelling has been collected for gulls in collaboration with Donana Biological Station and for fish in collaboration with Sportfisheries Netherlands (Milestone 4.1) the modelling has been developed (Milestone 4.2) and is now being applied (Milestone 3.2) to result in three publications that are in preparation (Deliverable 4.1).
Progress beyond the state of the art:

Publication on dispersal of wetland species by waterbirds, highlighting secondary dispersal in Biology Letters
Publication on the potential of alien species to interfere with zoochory in aquatic systems, highlighting the overlooked status of this process in aquatic systems (as part of bridging terrestrial and aquatic research, WP1) in Frontiers in Plant Sciences
Developed new experimental protocol simulating digestion by waterbirds for use in many future projects
Supervised PhD student Peiyu Zhang, Utrecht University (graduated 28/09/2018)
Supervised PhD student Antonella Petruzzella, Utrecht University, The Netherlands (graduation planned 12/06/2019)
Thesis committee PhD student Victor Martín Velez, Doñana Biological Station, Spain (graduation expected 2021)
Supervisor PhD student María José Navarro Ramos, Doñana Biological Station, Spain (graduation expected 2022)

Expected results until the end of the project:

Manuscripts in preparation:
- preparing a manuscript linking seed dispersal effectiveness among frugivory, granivory and herbivory (result of symposium workshop 17th April, WP1)
- preparing a manuscript showing trait-based dispersal potential for 48 native European plant species based on the newly developed experimental protocol (WP2/3)
- preparing two manuscript modelling seed dispersal by fish and birds (WP4)
- preparing an editorial manuscript for the Research Topic in Frontiers in Ecology and Evolution

Socio-economic impacts and societal implications so far:

The socio-economic and wider societal impacts stem mainly from my activities to organize multiple wetland-oriented symposia that form deliberate bridges between academia and society. These symposia attract a lot of media attention, are visited by a diverse range of people and are platforms that highlight the importance of wetland conservation. They provide networking opportunities that broaden my own network, but also facilitate long-lasting interactions among societal groups such as consultancy agencies, waterboards, engineering companies, applied scientists and fundamental scientists. Economic benefits of these interactions are that scientific knowledge is transferred to end-users. Twitter also serves the purpose of forming bridges among these groups. For this reason I communicate via Twitter about scientific knowledge from myself, from the wetland symposia and from the Research Topic in Frontiers (that highlights the overlooked status of zoochory) that we organized.

Main output in the public media directly based on my own publications:
1. Darwin was right about bird vomit - Discover Magazine (17/11/2017)
2. Visetende vogels verspreiden indirect plantenzaden - Vroege Vogels (13/10/2017)
3. Vissende aalscholvers bewijzen theorie van Darwin - NatureToday (11/10/2017)
4. Aalscholver verbindt plantpopulaties via vis - Bionieuws (07/10/2017)
5. Storskarvens spybollar bekräftar Darwins teori - MyNewsDesk Sweden (04/10/2017)
Project summary picture