Seed dispersal on pastoral grazers in open mediterranean chaparral, Israel

The effectiveness of external seed transport (epizoochory) on sheep, goats and man was studied experimentally in open, grazed chaparral in Israel. The animals were introduced into a permanent study area of known floristic composition, and the numbers of diaspores attached to their fur were recorded. Dyed diaspores of twenty species were attached to the fur of sheep and goats, and the numbers of diaspores remaining were monitored for several days. Significantly higher abundances on the animals (relative to abundance in the study area) were observed for diaspores having well-developed morphological characters (such as barbs and hooks) conventionally regarded as adaptations for attachment to animals. These diaspores also had significantly longer retention times on sheep and goats and could remain attached for periods of days to months. High abundances on the animals and long retention times were also observed in diaspores of Gramineae having characters most often interpreted as adaptations for burrowing into soil. Most of the species with effectively epizoochoric diaspores were annuals. It is hypothesized that seed transport on man and his grazing livestock may be a factor contributing to the maintenance of annual plant populations in grazed Mediterranean chaparral.