Metabolically active angiosperms survive passage through the digestive tract of a large-bodied waterbird

Plant traits associated with seed dispersal by ducks and geese in urban and natural habitats

Ducks and geese are little studied dispersal vectors for plants lacking a fleshy fruit, and our understanding of the traits associated with these plants is limited. We analyzed 507 faecal samples of mallard (Anas platyrhynchos) and Canada goose (Branta canadensis) from 18 natural and urban wetlands in England, where they are the dominant resident waterfowl. We recovered 930 plant diaspores from 39 taxa representing 18 families, including 28 terrestrial and five aquatic species and four aliens. Mallards had more seeds and seed species per sample than geese, more seeds from barochory and hydrochory syndromes, and seeds that on average were larger and from plants with greater moisture requirements (i.e., more aquatic). Mallards dispersed more plant species than geese in natural habitats. Plant communities and traits dispersed were different between urban (e.g., more achenes) and natural (e.g., more capsules) habitats. Waterfowl can readily spread alien species from urban into natural environments but also allow native terrestrial and aquatic plants to disperse in response to climate heating or other global change. Throughout the temperate regions of the Northern Hemisphere, the mallard is accompanied by a goose (either the Canada goose or the greylag goose) as the most abundant waterfowl in urbanized areas. This combination provides a previously overlooked seed dispersal service for plants with diverse traits.

Survival Strategies of Duckweeds, the World's Smallest Angiosperms

Duckweeds (Lemnaceae) are small, simply constructed aquatic higher plants that grow on or just below the surface of quiet waters. They consist primarily of leaf-like assimilatory organs, or fronds, that reproduce mainly by vegetative replication. Despite their diminutive size and inornate habit, duckweeds have been able to colonize and maintain themselves in almost all of the world's climate zones. They are thereby subject to multiple adverse influences during the growing season, such as high temperatures, extremes of light intensity and pH, nutrient shortage, damage by microorganisms and herbivores, the presence of harmful substances in the water, and competition from other aquatic plants, and they must also be able to withstand winter cold and drought that can be lethal to the fronds. This review discusses the means by which duckweeds come to grips with these adverse influences to ensure their survival. Important duckweed attributes in this regard are a pronounced potential for rapid growth and frond replication, a juvenile developmental status facilitating adventitious organ formation, and clonal diversity. Duckweeds have specific features at their disposal for coping with particular environmental difficulties and can also cooperate with other organisms of their surroundings to improve their survival chances.

Metabolically active angiosperms survive passage through the digestive tract of a large-bodied waterbird

Avian vectors, such as ducks, swans and geese, are important dispersers of plant propagules. Until recently, it was thought that small vegetative propagules were reliant on adherence to vectors and are unlikely to survive passage through the avian digestive tract. Here, we conclusively demonstrate that metabolically active angiosperms can survive passage through the digestive tract of a large-bodied waterbird. In addition, we show that extended periods of air exposure for up to 7 days does not inhibit the survival of plantlets embedded in faecal matter. Following air exposure, plantlets (n = 3000) were recovered from 75 faecal samples of mute swans, Cygnus olor, with the survival of 203 plantlets. The number of recovered and surviving plantlets did not significantly differ among durations of air exposure. For recovered plantlets, the long-term viability and clonal reproduction of two duckweed species, Lemna minor and L. gibba, were confirmed following greater than eight months of growth. These data further amplify the key role of waterbirds as vectors for aquatic plant dispersal and demonstrate the internal transport (i.e. endozoochory) of metabolically active plantlets. These data suggest dispersal of vegetative plant propagules by avian vectors is likely to be a common occurrence, underpinning connectivity, range expansion and invasions of some aquatic plants.