The Chestnut Ridge population of Sisyrinchium dichotomum in South Carolina has experienced a drastic decline in population count since 1998. Invasive epigeic earthworms have made an appearance in recent years; they are known to alter plant community composition by changing soil structure, depleting the humus layer, and selectively removing seeds from the seed bank through ingestion and digestion. In the lab, we conducted a pilot study of the ingestion/digestion of S. dichotomum seeds by the epigeic earthworms found at the site. In the field, we determined soil depth associated with each plant and made observations on plant condition, presence of a humus layer, and presence of worm castings. Epigeic earthworms ingested and digested significantly more S. dichotomum seeds than the anecic nightcrawler, Lumbricus terrestris. However, the epigeic worms liquefied within two days of ingestion, pointing to potential toxic effects of S. dichotomum seeds. We found a significant correlation between plant condition and soil depth. Plants in good condition were found in deeper soils than plants in poor condition. The humus layer was thin to absent around all plants and worm castings were ubiquitous. The depletion of the humus layer is especially important on south-facing slopes, the preferred habitat of S. dichotomum throughout its range. Experiments are planned that test the hypothesis that epigeic earthworms, via their rapid consumption of humus, negatively affect seed germination and seedling establishment, as well as plant condition.
P14 • Maitlyn E. Mullen, Jessica L. Fleming, Lawrence J. Davenport, Kristin A. Bakkegard, Elizabeth G. Dobbins
Revegetation of an Urban Riparian Zone: Species Richness and Population Dynamics
The analysis of revegetation efforts requires consideration of both planted and volunteer species. This study was conducted to measure the current species richness of native and invasive species from the 2011 revegetation of 160 meters on the south bank of Shades Creek in Jefferson County, Alabama. We predicted that there would be a greater number of invasive species than native species established by either seed, seedling or tree planting in 2011. In the restored site, we found a higher species richness and average percent cover for invasive species than native species and a lower percent survival for those native species planted in 2011. Only 6 out of the original 47 native species planted in 2011 survived. In the 2 control sites, we had 2 zones: riparian and upper bank. In the control zones, invasive species had higher species richness and average percent cover, except in the riparian zone of the second control. Richness and average percent cover in the controls was less than in the revegetated site. Recolonization of native species is still occurring in the revegetated site, but the majority of native species present are not those that were planted in 2011. In the future, restoration efforts should not focus on extensive planting of native species, but should concentrate on supporting natural self-restoration through better removal techniques to prevent the reinvasion and spreading of invasive species.
The Potential Pollinators of Schweinitz Sunflower (Helianthus schweinitzii ), Asteraceae
(Helianthus schweinitzii) as an endangered species. Native populations are found in the Piedmont of the Carolinas. In Fall 2013, populations located in the Winthrop Recreation & Research Complex and Blackjacks Heritage Preserve were observed to identify pollinators of this sunflower. Potential pollinators include insects from the orders Hymenoptera, Diptera, and Coleoptera. The Eastern carpenter bee (Xylocopa virginica) appears to be one of the most important pollinators. However, many other insects appear on the inflorescences often enough to be considered intentional or unintentional pollinators. Further research will focus on the observation of the frequency and time that each pollinator visits the inflorescences.
1 Biology Dept, Winthrop University Rock Hill, SC; 2 Biology Dept, Winthrop University Rock Hill, SC
P16 • Samuel Watkins, Theron Kantelis, N. Royce Dingley, Patrick Felch, Martin L. Cipollini
The First Tests of Blight-Resistance in Backcross Hybrid American Chestnuts (Castanea dentata) in Georgia: An Assessment of Leaf, Stem, and Bud Traits
The American Chestnut Foundation (TACF) uses backcross breeding to create hybrid American chestnuts (Castanea dentata) with resistance to blight (Cryphonectria parasitica) originating from Chinese chestnut (Castanea mollissima) parents. This process successively backcrosses hybrids to American chestnut thereby increasing the proportion of American genes in each generation. At each step, hybrids are selected for blight resistance and for morphological traits fitting an American chestnut phenotype. In 2008, three lines of 3rd backcross (BC3) hybrids were planted at Berry College, Georgia, along with American, Chinese, and F1 controls. The BC3 lines were the first bred using American chestnuts from Georgia (as part of TACF’s state chapter program). Trees were inoculated with blight in June 2013, and level of resistance was assayed in October 2013. At that time, branch samples were collected from all trees and used to evaluate 26 leaf, stem, and bud traits known to differ between American and Chinese chestnuts. With few exceptions, significant differences were found between the traits of Chinese and BC3 lines. A species identity index was derived by averaging standardized scores for all morphological traits, with low scores representing the American phenotype. Comparisons of this index sorted out genetic lines as predicted based upon the degree of American parentage. Several trees within each BC3 line had both good blight resistance and a highly American chestnut phenotype - a result consistent with the goals of TACF’s breeding program. Blight resistance will be reassessed in May 2014, and additional phenotypic traits will be considered prior to making final selections.
