Phenotypic Plasticity of Dispersal Characteristics of the Invasive Thistle Carduus nutans in Response to Mowing and Fertilizer
Open Access
Author:
Saperstein, Jonathan Charles
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Katriona Shea, Thesis Supervisor Dr. Bernhard Lüscher, Thesis Honors Advisor
Keywords:
Carduus nutans dispersal phenotypic plasticity
Abstract:
Carduus nutans L. (Asteraceae) is a species of invasive thistle that is native to Europe and can be found in central Pennsylvania, as well as in many other places throughout the United States, Australia, and New Zealand. Because of its invasive nature, it competes with local flora for resources and often has a very detrimental effect on farmland and pastures. This can be crippling to agriculture and have major economic implications, which is why effective management strategies for this weed are crucial.
In this study we examined C. nutans’ seed dispersal capabilities and how the use of varying treatment regimes in the field affects certain characteristics that are important for the dispersal and spread of the plant. We manipulated two factors in a fully-crossed experimental design: the addition (or lack) of fertilizer and the presence (or absence) of mowing. Plant height, terminal velocity, and seed production were analyzed. There was no significant effect of treatment on seed terminal velocity of the plants. However, across all treatments a relationship was seen between plant height and terminal velocity (taller plants had slower seeds). Moreover, mowed plants had significantly shorter final heights than those that were not mowed. Using a fluid dynamic model of seed dispersal by wind, the WALD model, we found that these mowed plants had a dispersal kernel that was significantly reduced compared to that of the unmowed plants. Reduced seed dispersal distance reduces spread, and our results suggest that mowing can be used as a way to manage the spread of this invasive and problematic thistle.
