6.7.23

Long-distance dispersal of aquatic invertebrates by ducks increases with propagule size

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Migratory ducks are key dispersal agents for aquatic organisms. Some groups are, however, particularly understudied. Despite consistent evidence of the potential  role of waterbird-mediated dispersal for aquatic invertebrates, and the key role of this group in the functioning of aquatic ecosystems, most evidencece remains anecdotal - or it is restricted to the collection of viable propagule in waterbird faces collected in the wild

In the article 'Evidence that long-distance dispersal of aquatic invertebrates by ducks increases with propagule size', which got published yesterday in Freswater Biology, researchers from the Doñana Biological Station and the Netherlands Institute of Ecology (NIOO-KNAW) teamed up to explore the potential for short- and long-distance dispersal of aquatic invertebrates, using a combinsation of experimental evidence and process-based modelling .

Using seven species of aquatic invertebrates and a duck species known to feed on them in the wild (the northern shoveler) as a model system, we evaluated whether their potential for endozoochorous dispersal varies among species, and the role of propagule size and morphology (e.g., the number of protective layers) in explaining such variation.  We also tested the expectation of a lower dispersal potential for invertebrate propagules, as compared to plant seeds; and evaluated whether intra-specific variation (in particular, sexual dimorphism) influences the potential of waterbirds as dispersal vectors.

Results showed that endozoochory of invertebrate propagules by waterbirds results in frequent dispersal among wetlands (tens of km) and regular dispersal at regional scale (over a hundred km). Increasing propagule size had two contrasting effects on invertebrate dispersal potential, decreasing the frequency of dispersal (fewer seeds dispersed) but increasing the potential for long-distance dispersal.