Demography of invasive black and pale swallow-wort populations in New York

Vincetoxicum nigrum (Black Swallow-wort) and Vincetoxicum rossicum (Pale Swallow-wort) are perennial, twining vines introduced from Europe. Both species have become invasive in northeastern North America in a variety of habitats. To develop parameters for a population model for evaluating the control of swallow-worts, including biological control, we collected data from 5 life stages on 20 different demographic rates involving fecundity, germination, survival, and growth. We monitored 2 field and 2 forest populations of Pale Swallow-wort, and 2 field populations of Black Swallow-wort in New York State using a combination of marked individuals and sowing plots. Both species showed moderate to high rates of seed germination and high survival of seedlings, with the primary exception of a heavily shaded forest population. Survival generally continued to remain high postestablishment, although transitions to different life stages varied by species, location, and habitat. Black Swallow-wort became reproductive more quickly than Pale Swallow-wort. These data add to the knowledge of swallow-wort demography and may offer insights into the continued expansion and control of these invasive plants.