| Summary: | Seed dispersal by herbivorous mammal endozoochory can be an efficient means of transport to new habitats, and may be especially important in poorly vegetated sites where there is little existing seed pool. In Iceland, where there are no indigenous large herbivores, the high numbers of freely grazing sheep in poorly vegetated summer grazing lands, may have a significant role as seed dispersers. To gain insight into the role of endozoochorous dispersal, 16 samples of sheep dung were collected at Skeiðarársandur, a glacial outwash plain in SE-Iceland. Dung samples were collected in August and October 2015 and grown in a greenhouse environment. Results showed that sheep on Skeiðarársandur disperse various species through endozoochory, yet were preferentially selective in the consumption of species dispersed. Sheep dispersed 25.8% of the available species recorded on Skeiðarársandur. Of the 24 dispersed species, 8 species had not yet been identified in the representative vegetation for the area. Species considered rare in abundance on Skeiðarársandur, represented 54 % of dispersed species, supporting the idea sheep are preferentially selective in plant consumption. Contrary to expectations, there was no correlation between proportion of dispersed species and seed mass and plant height. Species with high palatability, expected to disproportionally represent dispersed species, represent 42 % of dispersed species. Selective dispersal by sheep endozoochory may potentially play a key role in species diversity and richness, especially as it relates to sites of primary succession, where there is only a small and species-poor local seed pool.
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