JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Applied Ecology. Summary 1. In June to September 1993 a transhumant flock of sheep on the Schwabische Alb was examined with respect to which plants and animals are transported on and in the wool of sheep within calcareous grasslands. Several factors possibly influencing the attachment and detachment of diaspores on fleeces were studied, as well as the distribution of diaspores on the various body-parts of a sheep. The effects of different modes of sheep locomotion on dispersal were examined with the help of a sheep dummy. In order to assess the retention time of diaspores and animals on sheep, some experiments with marked diaspores and animals were carried out on two tamed sheep. 2. In 16 intensive examinations of the fleece of a single sheep, over 8500 diaspores of 85 vascular plants species were found. The highest numbers of diaspores were attached at the breast and neck of the sheep.3. Height of diaspore presentation, surface structure of diaspores and sheep locomotion were found to be the decisive factors for the reception and transport of diaspores in the wool. In addition, plant frequency and the length of the disseminating period are of importance. 4. Marked diaspores with both adhesive and smooth surfaces remained on the sheepskin for up to seven months, and can consequently be dispersed over the entire roaming area of the sheep. 5. Amongst the animals transported by sheep, only grasshoppers (13 species) were observed frequently on the flock of sheep. The period of time marked grasshoppers stayed on sheep ranged from 1 to 69 min, with an average of 14 min. During this period sheep can cover distances of over 100 m when grazing and well over 500 m when roaming. 6. Our study indicates that the importance of the dispersal of diaspores, and especially animals, by animals has so far been largely underestimated. This is mostly due to the methods previously used to examine dispersal mechanisms. 7. Conservation management of rare and endangered species should consider the importance of sheep for maintaining the species richness of calcareous grasslands. It is likely that transhumant sheep farming is irreplaceable in the restoration of grasslands threatened by fallow and woody successional stages. Moreover, traditional shepherding facilitates the exchange of individuals of both plants and animals between isolated patches. That is, sheep are able to maintain dynamic processes even in our greatly fragmented landscape; this is probably essential to long-term population viability of many species.

Species richness in calcareous grassland is discussed against the background of historical dispersal processes associated with traditional land-use management such as grazing, but also the artificial establishment by hayseed. Important vectors in the traditionally man-made landscape were sheep and cattle or other livestock such as goats. Calcareous grasslands were not only connected to each other but also to other habitats such as villages, forests, arable fields and heathlands by these vectors which could cover large distances (e.g. transhumance shepherding), which is not the case in the current man-made landscape.Species richness after restoration management of abandoned and afforested calcareous grasslands was predicted by using characters of dispersability in space and time. These were the persistence of the species in the vegetation and the diaspore bank after abandonment or afforestation and the dispersal capacity through wind and sheep. The results reveal that reintroduction of sheep grazing is necessary to reestablish the original species richness. The first validation of the prediction of the succession on clear-cut sites and a comparison with data of species composition in abandoned quarries and the surroundings made it obvious that a species' own dispersal capacity in space is very low except for some well winddispersed species. Therefore, it is recommended to include and to simulate dispersal processes in future management to be able to restore the original species richness.

A loss of lymphatic identity seems to be the underlying cause for clinical NE. Also, abnormal endothelial differentiation provides a link to the cardiovascular anomalies associated with NE.