Large herbivores as mobile links between isolated nature reserves through adhesive seed dispersal

Question: Do large herbivores contribute to the dispersal of plant seeds between isolated habitats by epizoochory? Location: Nature reserves in Flanders, Belgium. Methods: Epizoochory was studied by brushing plant seeds from the fur of 201 domesticated large herbivores (Galloway cattle, donkeys and horses), grazing in 27 Flemish nature reserves. Several herbivores were examined after transport between different nature reserves as part of the seasonal grazing system in Flanders, allowing detection of seed dispersal both within and between reserves. The seedling emergence method was used to identify the dispersed plant species. Results: In total, 6385 epizoochorous seeds from 75 species germinated, yet the real seed quantity was underestimated by the seedling emergence method. A wide variety of seed morphology, seed weights and plant heights was represented among the dispersed species, many of which had a transient seed bank. There was a gradual turnover in epizoochorous species composition in the course of the vegetation season, and seed dispersal occurred both within and between different nature reserves. Conclusions: Domesticated large herbivores, as models for wild mammals in the present and the past, are important dispersers of many plant species. Through seasonal grazing, the herbivores function as ‘mobile link organisms’, connecting isolated nature reserves through seed dispersal, possibly influencing vegetation development and long‐term survival of plant populations. As such, large herbivores are important instruments in ecological restoration, especially in fragmented ecosystems.     

Avian seed dispersal and seedling distribution of the endangered tree species,Taxus chinensis,in patchy habitats

Background: There is limited understanding about bird dispersal behaviour and seedling distribution of endangered tree species in patchy environments, although these processes are important for plant species persistence.

Aims: We tested how patch features affected bird behaviour and seed dispersal, and thus seedling distribution of the endangered Chinese yew tree (Taxus chinensis).

Methods: In the present study, we combined field data of bird dispersal behaviour and GIS-based information to elucidate the influence of spatial features of habitat patches on bird dispersal behaviour, and the resulting effects on the seedling distribution of the endangered Chinese yew in two patchy habitats.

Results: Our results showed that the only seed source patch could attract eight bird species for dispersal at the two sites. Post-foraging movements of bird dispersers was strongly related to both topography and the relative locations of habitat patches. Yew seedlings aggregated only at the seed source and bamboo recruitment patches, which was affect by both the spatial distribution of recruitment patches and patch use by dispersers.

Conclusions: Our results emphasise that bamboo patches in both patchy environments provide the necessary conditions for germination of yew seeds, and the post-foraging behaviour of dispersers determines seed deposited in these patches. Our study highlights the importance of the dispersal behaviour of frugivorous birds in the successful regeneration and colonisation of yew populations in patchy habitats.     

Genetic variation in an ephemeral mudflat species: The role of the soil seed bank and dispersal in river and secondary anthropogenic habitats

Many ephemeral mudflat species, which rely on a soil seed bank to build up the next generation, are endangered in their natural habitat due to the widespread regulation of rivers. The aim of the present study was to elucidate the role of the soil seed bank and dispersal for the maintenance of genetic diversity in populations of near‐natural river habitats and anthropogenic habitats created by traditional fish farming practices using Cyperus fuscus as a model. Using microsatellite markers, we found no difference in genetic diversity levels between soil seed bank and above‐ground population and only moderate differentiation between the two fractions. One possible interpretation is the difference in short‐term selection during germination under specific conditions (glasshouse versus field) resulting in an ecological filtering of genotypes out of the reservoir in the soil. River populations harbored significantly more genetic diversity than populations from the anthropogenic pond types. We suggest that altered levels and patterns of dispersal together with stronger selection pressures and historical bottlenecks in anthropogenic habitats are responsible for the observed reduction in genetic diversity. Dispersal is also supposed to largely prohibit genetic structure across Europe, although there is a gradient in private allelic richness from southern Europe (high values) to northern, especially north‐western, Europe (low values), which probably relates to postglacial expansion out of southern and/or eastern refugia.