Survival and performance of the invasive vine Vincetoxicum rossicum (Apocynaceae) from seeds of different embryo number under two light environments.

The nonnative vine Vincetoxicum rossicum threatens several ecosystems in the Lower Great Lakes Basin of North America. One feature that may contribute to its invasiveness is the production of some seeds with multiple embryos (polyembryony), which may be beneficial as a bet-hedging strategy in variable environments. However, lower seed reserves per embryo in polyembryonic seeds may entail costs in low-light environments. The effect of seed from three embryonic classes (1, 2, or 3 embryos/seed) on V. rossicum survival and growth was studied under two forest understory light environments: full canopy (shade) or canopy gaps (light) in New York state. Two seedling cohorts were planted, in May 2004 and in May 2005. The survival and growth of seedlings was monitored biweekly for two (2005 cohort) or three (2004 cohort) seasons. For both cohorts, plants grown in canopy shade had reduced survival and growth compared with those grown in gaps. Contrary to expectations, seed embryo number had no effect on the final height, survival, or dry mass of plants in either habitat. Our results suggest that any fitness advantage provided by polyembryony may be habitat (light) dependent and not a general trait that affords V. rossicum a benefit in all habitats colonized.