Dispersal distances and predation rates of sexual and asexual propagules of Allium vineale L

The ecological characteristics of two propagule types of Allium vineale (sexually produced seeds and asexually produced bulbils) were studied to identify factors which could lead to the maintenance of both propagule types as reproductive mechanisms. Ecological traits studied were dispersal patterns, predation rates and longevity of propagules. Seeds and bulbils dispersed to the same average distance from the parent, but seeds occasionally traveled 10-30 cm further than bulbils. In addition, some bulbil infructescences were observed dispersing as a unit. Predation rates were significantly higher for seeds, but the density of propagules in an area had no effect on removal rates. Seeds and bulbils buried in the field were no longer viable after 1 yr. However, seeds stored in the laboratory for up to 3 yr had higher viability percentages than bulbils. Overall, the ecological differences found between seeds and bulbils are small relative to the differences found among dimorphic propagules of other species, and do not fit the predictions of models for the conditions necessary to maintain the production of heteromorphic propagules.