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

Authors: Milbrath, Lindsey; Davis, Adam; Biazzo, Jeromy

Submitted to: Northeastern Naturalist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2016
Publication Date: 3/31/2017
Citation: Milbrath, L.R., Davis, A.S., Biazzo, J. 2017. Demography of invasive black and pale swallow-wort populations in New York. Northeastern Naturalist. 24:37-53.

Interpretive Summary: Pale and black swallow-wort are exotic, invasive weeds of natural areas and managed lands in northeastern North America. Gaps remain in our knowledge of how populations of these plants change over time and how potential biological control agents may alter swallow-wort population growth. As a first step, we studied the survival, growth, and reproduction of different life stages of pale and black swallow-wort over time in field habitats and, for pale swallow-wort only, forest habitats. Both species had moderate to high seed germination and generally high survival of the seedling through adult stages at most locations and in different habitats. Black swallow-wort matured to a flowering stage more quickly than pale swallow-wort. Variability in results among locations suggests that different swallow-wort populations will need to be assessed separately. This information will be incorporated into plant models for evaluating the potential effectiveness of biological control.

Technical Abstract: 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 potential biological controls for Swallow-worts, we collected data from five life stages on 20 different demographic rates involving fecundity, germination, survival, and growth. Two field and two forest populations of Pale Swallow-wort, and two field populations of Black Swallow-wort, were monitored 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 post-establishment although transitions to different life stages varied by species, location, and habitat. Black Swallow-wort notably became reproductive more quickly than Pale Swallow-wort. These data add to the knowledge of Swallow-wort demography and may offer insights into their continued expansion and control.