Abstract:-Japanese honeysuckle (Lonicera japonica) is an invasive vine that is currently outcompeting its native congener coral honeysuckle (Lonicera sempervirens). Some studies have demonstrated that in response to herbivory and CO2 enhancement, L. japonica was more plastic than its native congener. L. japonica has also been shown to be more morphologically plastic than L. sempervirens in response to climbing supports. The goal of this study was to compare morphological plasticity of L. japonica and L. sempervirens in response to light. My hypothesis was that L. japonica would show greater plasticity than would the L. sempervirens. The study included seventy-two honeysuckle plants that were grown in three separate light treatments-30% neutral shade, 70% neutral shade, and 70% green film. The two neutral shade treatments were used to measure the effect of light intensity; and the two 70% shade cloths, neutral and green, were used to measure the effects of light wavelength. Four different morphological variables were measured on each plant: internode length (cm) on the primary shoot, internode length (cm) of the lateral shoots, branching index , and the lateral angles (angle of the first lateral in relation to primary shoot). I predict, based on past evidence, that L. japonica will show stronger phenotypic plasticity in conjunction with all four morphological variables.

Key words: Caprifoliaceae, honeysuckle, invasive species, light availability, Lonicera, phenotypic plasticity, plant foraging