Title: Demographic matrix model for informing swallow-wort (Vincetoxicum spp.) biological control Authors
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: February 4, 2013
Publication Date: February 4, 2013
Citation: Milbrath, L.R., Biazzo, J., Davis, A.S. 2013. Demographic matrix model for informing swallow-wort (Vincetoxicum spp.) biological control. Weed Science Society of America Meeting Abstracts. http://wssaabstracts.com/public/17/abstract-204.html. Technical Abstract: Demographic matrix modeling of plant populations can be a powerful tool to identify key life stage transitions that contribute the most to population growth of an invasive plant and hence should be targeted for disruption (weak links) by biological control and/or other control tactics. Therefore, this approach has the potential to guide the selection of effective biological control agents. We have parameterized a five life-stage matrix model in order to generate pre-release agent recommendations for the swallow-wort biological control program. Pale swallow-wort (Vincetoxicum rossicum) and black swallow-wort (V. nigrum) are herbaceous, perennial, viny milkweeds introduced from Europe (Apocynaceae-subfamily Asclepiadoideae). Both species are becoming increasingly invasive in a variety of natural and managed habitats in the northeastern United States and southeastern Canada. Black swallow-wort appears restricted to higher light environments, whereas pale swallow-wort infestations occur from the high light environments of open fields to low light forest understories. We quantified demographic transitions for marked individuals of the five life stages over 3-4 years of both swallow-wort species in field and, for pale swallow-wort, forest habitats in New York State (N = six populations). Vital rates estimated include germination, survival, growth to the next life stage, and fecundity (viable seeds produced per plant). All open field populations of both swallow-wort species as well as a high-light forest population of pale swallow-wort are increasing (population growth rates > 1). However, a heavily shaded (low-light) forest population of pale swallow-wort is only persisting (population growth rate = 1). Elasticity analyses have identified several potentially important transitions for one or both species of swallowwort: survival of vegetative juvenile, small flowering and large flowering plants; growth of seedlings, juveniles and small flowering plants to the next life stage; and reproduction of small and large flowering plants. This information in combination with published herbivory impact data will be used to assess the potential efficacy of candidate biological control agents. Successful biological control of long-lived perennials like the swallow-worts will likely require targeting a combination of either survival and growth transitions or survival and reproduction transitions.