Enhancement of local species richness in tundra by seed dispersal through guts of muskox and barnacle goose.

The potential contribution of vertebrate-mediated seed rain to the maintenance of plant community richness in a High Arctic ecosystem was investigated. We analyzed viable seed content in dung of the four numerically most important terrestrial vertebrates in Northeast Greenland - muskox (Ovibos moschatus), barnacle goose (Branta leucopsis), Arctic fox (Alopex lagopus) and Arctic hare (Lepus arcticus). High numbers of plant propagules were found in the dung of muskox and barnacle goose. Seeds of many plant species were found in the faeces of one vertebrate species only. Propagule composition in barnacle goose droppings was relatively uniform over samples, with a high abundance of the nutritious bulbils of Polygonum viviparum (Bistorta vivipara), suggesting that geese have a narrow habitat preference and feed selectively. Propagule composition in muskox dung was diverse and heterogeneous among samples, suggesting a generalist approach in terms of food selection and the haphazard ingestion of plant propagules with foliage. The species composition of plant propagules in dung samples was different from that of the receiving plant communities (in terms of the Sørensen and Czekanowski dissimilarity indices), and dung deposition, especially by muskox, often brought new species to the receiving community. The results suggest that endozoochorous propagule dispersal in the Arctic has a great potential in the generation and maintenance of local species richness, albeit being little specialized. It is further suggested that endozoochory is an important means of long-distance dispersal and, thereby, of plant migration in response to climate change.