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Harvard Forest Symposium Abstract 2009

  • Title: Conservation while under invasion: insights from a rare, hemiparasitic plant, Swamp Lousewort (Pedicularis lanceolata Michx.)
  • Primary Author: Sydne Record (Harvard Forest)
  • Abstract:

    It is commonly held that invasive species threaten rare, native species. Most studies focus on competitive interactions between invasive and rare species. This emphasis on competition may divert management attention away from other important types of interactions, such as facilitations between invasive and rare species with unique ecological interactions. For rare, generalist hemiparasitic plants that rely on host plants to complete their life cycles, the balance between facilitative and competitive interactions with co-occurring invasive plants is important in determining whether or not invasive species pose a threat.

    Swamp Lousewort (Pedicularis lanceolata) is a generalist hemiparasite that relies on additional nutrients and water from host plants, acquired by haustoria (root-connections between the hemiparasite and its host). Pedicularis lanceolata is regionally rare in New England. Competition with invasive species is a potential threat to P. lanceolata in Massachusetts; however, it is unclear whether invasive species in the vicinity of P. lanceolata act more as harmful competitors or as beneficial host plants to this rare species. To determine how to manage invasive species that co-occur with P. lanceolata, I ask three questions. 1) How does P. lanceolata respond to the removal of non-native and native species? A three-year field removal experiment addresses this question. 2) Do co-occurring invasive and native species interact with P. lanceolata positively as facultative host-plants or negatively as competitors? To answer this question, I am conducting a greenhouse experiment where P. lanceolata grows with different densities of invasive and native host plants with or without the effects of aboveground competition through a clipping manipulation. 3) What are the population trajectories and metapopulation dynamics of an invaded New England population of P. lanceolata? A three-year demographic study addresses this question.

    Preliminary results from the field removal experiment show that removing non-native plants increased the percentage of change in the total stem length of P. lanceolata by nearly 400%. Removing both native and invasive plants signigicantly decreased the percentage of change in the total stem length of P. lanceolata (one-way ANOVA, d.f. = 8, F = 12.75, P = 0.002). The greenhouse experiment is underway and will be completed this summer. This growing season, I will collect the final year of demographic data for the population modeling.

  • Research Category: Conservation and Management, Invasive Plants, Pests & Pathogens, Physiological Ecology, Population Dynamics, and Species Interactions