A field study of seed dispersal and seedling performance in the invasive exotic vine Vincetoxicum rossicum

The exotic vine Vincetoxicum rossicum (Kleopow) Barbar. (Asclepiadaceae) is a major natural-areas pest throughout the Great Lakes Basin. Colonization of new areas by this herbaceous perennial occurs by comose wind-dispersed seeds. Previous experiments suggested a trade-off between seed dispersability and seed quality: smaller seeds dispersed farther but were less likely to emerge and seedlings were smaller when grown in competition with turf grasses in the greenhouse. We examined dispersability by trapping seeds at distances of 0–60 m from a seed source, and we assessed seedling performance by sowing seeds of known weight in an old field. Smaller seeds travelled significantly farther than larger seeds; however, the relationship between weight and distance dispersed was weak (r2 = 0.043). Large seeds were significantly more likely to emerge, and the seedlings survive and grow taller; however, the relationships between seed size and these performance variables were also weak (r2 £ 0.02). The dispersability–quality tradeoff is unlikely to play an important role in V. rossicum spread at the local scale, as even large seeds are competent dispersers and even seedlings from small seeds are capable of becoming established. Seedlings from polyembryonic seeds were more likely to successfully establish than seeds from which a single seedling emerged. The high seedling emergence (50% for seeds planted above ground; 72% for those buried to a depth of 1 cm) and survivorship (71%–100%, depending on embryony) are likely to contribute to the success of this species.