Effects of seed passage by sheep on germination of the invasive Prosopis juliflora tree

Prosopis juliflora is a small mesquite tree native to Central and South America, with invasive populations in many tropical and subtropical regions worldwide, including North Africa and the Arab Gulf region where it has been introduced for livestock forage. In Egypt, the geographical pattern of its spread suggests that domestic sheep are important seed vectors. We assessed the effect of seed passage through the sheep digestive system on germination. Only 7 % of seeds passed through the digestive system intact, and these seeds had greater volume and weight. Excreted seeds had higher germination rates and germinated more quickly than untreated control seeds under laboratory conditions. Our results further strengthen evidence for the importance of domesticated animals as vectors of this invasive species and suggest that sheep must be considered in management strategies to prevent further spread into protected areas.