Abstract
BackgroundEndozoochory is, in grazing systems, a substantial vector for seed dispersal. It can play an important role in vegetation dynamics, especially in colonization processes through seed input on the vegetation and on the soil seed bank. We investigated the endozoochorous seed input of donkeys and goats on a semi-natural island ecosystem in the Mediterranean. Through germination experiments, we assessed the viable seed content of the dung of these grazing animals to estimate their suitability and efficiency for seed dispersal of the vegetation types of the island.ResultsWe show different dispersal patterns of donkeys and goats. Goats disperse a high number of diaspores from shrubs while donkeys disperse more diaspores of grasses. In addition, goats disperse plants of greater growth height and donkeys plants of shorter height. These dispersal patterns are in accordance with the vegetation types of which donkeys and goats disperse indicator species. Both, donkeys and goats, feed on and disperse species of the vegetation types, open grassland and temporarily wet grassland. In addition, goats feed on and disperse diagnostic species of the semi-open maquis and preforest formations.ConclusionsOverall, our results show that donkeys and goats are complementing each other in their endozoochorous seed dispersal potential. This emphasizes the importance of both grazing animals for the vegetation dynamics of the semi-natural island ecosystem. Therefore, the adaption of the goat management to a traditional land management based on directed transhumance might maintain and enrich vegetation types.
Highlights
Endozoochory is, in grazing systems, a substantial vector for seed dispersal
The digital mapping of the main vegetation types of the island (Additional file 1) revealed that most of the area of the island is dominated by semi-open maquis with Euphorbia dendroides, garrigue with Cistus monspeliensis shrubs and open grassland with annual graminoids, annual forbs and legumes
Donkeys and goats, disperse the highest number of seedlings of the functional type sedges and rushes with a high occurrence of Juncaceae which produce a high number of small sized seeds following the assumption that plants producing small seeds entail a high number of seeds [55, 56]
Summary
Endozoochory is, in grazing systems, a substantial vector for seed dispersal. It can play an important role in vegetation dynamics, especially in colonization processes through seed input on the vegetation and on the soil seed bank. In the Mediterranean region endozoochory by herbivores plays an important role [8, 9] as has been shown that, in grazing systems, on average, 740 seeds per square metre are dispersed endozoochorously [9]. The long history of livestock farming has promoted the adaptability of plants to grazing [10] Through their dung animals, like sheep and hare, disperse a high number of plant species the effect of the passage through
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