Effects of salinity and ingestion by ducks on germination patterns of Juncus subulatus seeds

Changes in the nature of the seed coat caused by gut passage are considered to be the proximate causes of changes in germination patterns. Modifications of seed coat permeability may be decisive in saline environments (e.g. Mediterranean wetlands), in which the response of the seed to osmotic stress, or its resistance to toxicity caused by some ions may be affected. We analysed how passage through a duck gut can change the response pattern of seeds of a Mediterranean helophyte Juncus subulatus to an experimental salinity gradient. Gut passage produced (1) a significant loss of seed viability (about 30%) across the whole salinity gradient and (2) no change in the intrinsic variability of the dormancy period or germination rate in J. subulatus seeds. However, J. subulatus seeds clearly have the potential to disperse via birds. We compare our results with those obtained previously for sympatric species of saline environments.