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Keywords:

  • Archipelago;
  • Biodiversity;
  • Dispersal distance;
  • Historical ecology;
  • Human-mediated dispersal;
  • Long-distance dispersal;
  • Rotational grazing

Abstract

Question

To what extent does the movement of animals between fragmented habitat patches provide functional connectivity via endozoochorous seed dispersal?

Location

The Stockholm archipelago, Sweden.

Methods

We followed all movements of livestock between islands during one grazing season. After each movement, manure was collected and its seed content assessed through seedling emergence. Seedling data were then compared to vegetation surveys from the grazed islands with regard to functional traits.

Results

Light- and nitrogen-demanding locally abundant species, and those with relatively small and persistent seeds were more likely to be moved between islands. For quantitative traits, only a subset of the available trait ranges were dispersed, with extreme values left behind. Species apparently specialized to other means of dispersal emerged from the manure samples. Neither dispersed traits nor seed density changed with timing of movement, but seed richness and diversity both increased throughout the season. The subsets of endozoochorously-dispersed species in the established vegetation were more similar than non-dispersed subsets between islands linked by livestock.

Conclusions

Grazing networks contribute to the connectivity of the core species in the system, and could provide useful tools for grassland management in fragmented landscapes.