Cattails and Allelopathy
Second to habitat destruction, the loss of biological diversity due to invasive species is the leading cause of extinctions. Understanding the mechanisms of invasiveness is necessary to control the spread of invasive species. Two invasion hypotheses, the Novel Weapons Hypothesis and the Hybrid Superiority Hypothesis, may be useful in explaining the invasiveness of Typha angustifolia (narrow-leaved cattail) and Typha x glauca (hybrid cattail), respectively. Both T. angustifolia and T. x glauca are invasive wetland plants that often form monocultures in disturbed wetlands. Dr. Meghann Jarchow's research objectives were to determine whether allelopathy is a mechanism that has contributed to the invasiveness of T. angustifolia and T. x glauca. To determine whether allelopathy is a mechanism of invasiveness in T. angustifolia, Meghann grew T. angustifolia with a native bulrush, Bolboschoenus fluviatilis (river bulrush) with and without activated carbon in a greenhouse. To further characterize the allelopathy in T. angustifolia, Meghann quantitatively and qualitatively analyzed the soluble bulk phenolics, a major class of allelochemicals, produced by T. angustifolia grown alone and T. angustifolia grown with B. fluviatilis. To determine whether T. x glauca had hybrid vigor regarding allelochemicals production, the soluble bulk phenolics produced by the roots and leaves of T. angustifolia, Typha latifolia (wide leaved cattail), and T. x glauca were analyzed. Meghann found that T. angustifolia reduced the fitness of B. fluviatilis through allelopathy. Additionally, the allelopathic response of T. angustifolia was regulated in the roots but not in the leaves providing support that the allelopathy in T. angustifolia occurs primarily through root exudates. Meghann also found that T. angustifolia, T. latifolia, and T. x glauca produced quantitatively and qualitatively different soluble bulk phenolics in the roots and leaves with T. x glauca producing more soluble bulk phenolics in the leaves than either parental species. This suggests that T. x glauca may have hybrid vigor regarding allelochemicals production. Future research should examine the importance of allelopathy in the invasiveness of T. angustifolia and T. x glauca in the field.