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Physiology as a Mechanism Driving Early Fitness Responses in Cornus Florida
Brendan Finnie, Depts. of Biology and Chemistry, and Jane L. Remfert, Graduate Student in Integrative Life Sciences, with Dr. Rodney Dyer, VCU Center for Environmental Studies
Urban encroachment into natural ecosystems can increase the chances cultivar gene escape from the urban environment into natural populations. Cultivar Cornus Florida, flowering dogwood, has been artificially selected for traits like larger floral displays, tolerance of high sunlight, and resistance to disease and occurs in close proximity to native populations. A common garden experiment was established to compare relative performance of cultivar and native seedlings in native shade conditions by measuring proxies for fitness. Additionally, physiological measurements were taken as a potential mechanism driving early differential fitness responses of seedlings. Light saturated photosynthesis was measured using a Li-Cor 6400 Portable Photosynthesis System, additionally, proxies for fitness like leaf area, height, stem diameter, and above and below ground biomass were collected. Image J was used to calculate leaf area from digital photos and linear mixed effects models were used to determine differences in plant traits between cultivar and native seedlings. Plant traits including above and below ground biomass were significantly larger in cultivar C. florida seedlings (AGB P = 0.019, BGB P = 0.005). There was a significant difference in leaf area (cm) from the leaf base to tip between cultivar and native seedlings (P < 0.001) but no significant differences were found in mean light saturated photosynthesis between native and cultivar C. florida seedlings (P = 0.792). The lack of differences in photosynthetic rate between native and cultivar C. florida seedlings does not support a physiological mechanism driving differential early fitness response. Differences in early fitness response indicate that cultivar C. florida can outperform native seedlings in a shaded understory environment. Thus, it is possible that cultivar genes that escape from urban areas could establish in native populations.
Rodney Dyer, Ph.D.
Virginia Commonwealth University. Undergraduate Research Opportunities Program
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