THE INFLUENCE OF HABITAT SUITABILITY, LANDSCAPE STRUCTURE, AND SEED DISPERSERS ON INVASION OF AN EXOTIC PLANT SPECIES, LONICERA MAACKII (RUPR) HERDER, AMUR HONEYSUCKLE
Although invasive plants are recognized as a major ecological problem, little is known of the relative importance of plant community characteristics versus landscape context in determining invasibility of communities. For animal-dispersed plants, invasion patterns may be influenced by landscape features that influence movement of seed dispersers. In this study, I investigated the relative importance of community and landscape features in the invasion of Lonicera maackii in woodlots in southwest Ohio. I also determined the bird species responsible for seed dispersal of this plant and the timing of fruit loss. I regressed Lonicera maackii presence and density separately against community and landscape characteristics quantified from 30 woodlots. Presence of L. maackii was significantly negatively associated with distance from the nearest town. Density of L. maackii was significantly positively related to amount of edge in the landscape and significantly negatively related to total tree basal area, number of native woody species, and sapling shade tolerance index. Analysis of seeds recovered from feces of birds mist-netted near fruiting L. maackii shrubs revealed four native and one exotic bird species dispersed viable L. maackii seeds. I performed feeding trials to determine the effect of gut passage on L. maackii seeds. Germination was inhibited by passage through Cedar Waxwings, but not through American Robins. Radio-tracked American Robins moved mostly along woodlot edges and fencerows, leading me to project that most viable seeds would be defecated in such habitats. I used fruit traps to determine the timing of fruit loss (abscission + removal). Fruit loss from L. maackii shrubs was significantly related to winter temperature and precipitation. Fruit removal by frugivores was greater in cold temperatures and low precipitation. In general there was no effect of temperature and precipitation on fruit abscission. This study shows that L. maackii invades through expansion of multiple foci and is facilitated by bird dispersal. Through bird dispersal, L. maackii is able to navigate the landscape and invade new suitable habitats. The interaction of L. maackii and American Robins involves a positive feedback loop, in which seeds are defecated in highly suitable habitat where the birds also forage on L. maackii fruits.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:lonicera maackii landscape features connectivity seed dispersal fruit abscission frugivory invasive species
Date of Publication:01/01/2004