Danny J. Gustafson

Environmental DNA (eDNA) is the genetic material that organisms leave in the environment. In this study, we collected water samples from four isolated wetlands in the Francis Marion National Forest in the winter (January) and spring (March), extracted environmental DNA (eDNA) and used species-specific mitochondrial genes to identify the presence of rare amphibian species. Currently, our target genes are COI (Cytochrome C Oxidase Subunit I) and ND2 (Subunit of NADH dehydrogenase). Our target species is the rare Gopher Frog (Lithobates capito), a fossorial species that emerges from upland longleaf pine habitats to breed in isolated temporary ponds after heavy rains. In addition, we are testing for the presence of potentially co-occurring species of the longleaf pine isolated wetlands (Southern Leopard Frog - Lithobates sphenocephalus, Southern Toad - Anaxyrus terrestris, Southern Chorus Frog - Pseudacris nigrita, Southern Cricket Frog - Acris gryllus, and Pine Woods Treefrog - Dryophytes femoralis). The Gopher frog was present in all four ponds on both sampling dates. Lithobates sphenocephalus was present in Sunset Pond in January and all four ponds in March. These results may contribute to a better understanding of amphibian phenology in isolated ephemeral wetlands of the longleaf pine ecosystem.

Coccoloba uvifera L. (seagrape) is a primarily dioecious neotropical tree species which often grows in the beach–forest transitional ecotone of coastal strand vegetation. We used five maternally inherited non-coding chloroplast regions to characterize the phytogeography of C. uvifera collected across the Caribbean Basin and Florida. Bayesian analysis revealed divergence between the Aruba–Trinidad–Tobago–Antigua–Jamaica island group and the continental Belize–Florida–US Virgin Islands (USVI) group at 1.78 million years before present (mybp), divergence between the Belize and Florida–USVI groups at 1.08 mybp, and a split of Antigua–Jamaica from Aruba–Trinidad–Tobago at 0.217 mybp. Haplotype network analysis supports the three clades, with the island group possessing the oldest haplotype. Based on geology and proximity, these clades correspond to South American (oldest), Central American, and North American (most recent). Coccoloba uvifera demographic expansion occurred during the Pleistocene epoch and peaked near the end of the last glacial maximum (ca. 0.026–0.019 mybp) when the global sea levels were 125 m lower than today. Our findings also reveal that tropical cyclones, which often impact coastal strand vegetation, did not affect genetic diversity. However, there was a positive association between latitude and the average number of substitutions, further enriching our understanding of the species’ phytogeography.

Hurricane Hugo was a category five storm in September of 1989 that significantly impacted natural areas along the Carolina coastal plain through wind damage and storm surge flooding. Francis Beidler Forest, an Audubon wildlife sanctuary in Four Holes Swamp, suffered severe damage to its forest canopy. In response to concerns that the rare spring ephemeral Trillium pusillum var. pusillum may be negatively impacted by the loss of the mixed hardwood canopy, we established permanent plots in the spring of 1990 with single leaf, triple leaf, and flowering individuals recorded by Ecology faculty and students at The Citadel. Disruption to the forest canopy would significantly alter forest floor microhabitat conditions negatively affecting T. pusillum var. pusillum population demography. There was no expected negative effect of Hurricane Hugo, and the loss of canopy cover on the population. Evidence suggests that the decrease in canopy cover and increased light was associated with increased flowering. The coefficient of variation, as a measure of cohort variability among years, increased from flowering, to triple leaf, to single leaf across the 29 years of population monitoring. There was a significant positive association between the number of named storms in the previous two and three years and the number of single leaf plants. There was no evidence that the population is decreasing, even though the number of flowering individuals has decreased. The results of this long-term demography suggest that even severe natural disturbances, like hurricanes and tropical storms, may have a positive effect on Trillium population dynamics.

Restoration of the herbaceous understory community of the longleaf pine ecosystem is limited by the availability of appropriate seeds. To understand the relationship of seed transfer zones and genetic composition of two co-occurring species of the herbaceous understory, seeds of little bluestem (Schizachyrium scoparium) and hairy lespedeza (Lespedeza hirta) were collected from five provisional seed transfer zones across the historical range of the longleaf pine ecosystem in the North American Coastal Plain as well as a commercially available seed source originating from outside this range. To determine the genetic structure and diversity of these plants within the seed transfer zones and the commercial source, microsatellite and inter-simple sequence repeats (ISSR) markers were used for little bluestem and hairy lespedeza, respectively. For both species, plants from within the five seed transfer zones were genetically distinct from the commercial source from Kentucky. Little bluestem and hairy lespedeza plants from two provisional seed transfer zones were more genetically similar to each other than they were to other seed zones, which could justify merging these two zones. The genetic relationships among the remaining seed zones, including the commercial source from Kentucky, roughly follow geographic proximity, with genetic similarity decreasing as a function of geographic distance. Most of the genetic variation was partitioned within and less among seed zones, despite documenting significant differences among seed zones. The results of this study support the sub–The Nature Conservancy ecoregion seed transfer zones while acknowledging species-specific differences among seed transfer zones for the longleaf pine ecosystem.

American chaffseed (Schwalbea americana L. [Scrophulariaceae]) is a federally endangered, hemiparasitic species that primarily occurs in fire-maintained pinelands in the Atlantic and Gulf coastal plains of the US. Efforts to propagate S. americana for reintroduction into the wild have been met with mixed results. Discrepancies in our understanding of host requirements, soil ecology, and growing conditions need to be resolved in order to develop a successful ex situ propagation program. We conducted a series of greenhouse experiments to address the impact that growth media, soil microbes, mycorrhizal associations, and autoparasitism may have on successful propagation of seedlings. We also tested the effectiveness of storing bareroot plants at 4 °C (39 °F) relative to plants overwintering outside or being maintained in the greenhouse. We confirmed that cold-moist stratification is necessary to achieve the high germination rates needed for ex situ propagation. Soil microbes and growth media affected S. americana survivorship. We successfully grew plants in the absence of host plants by supplementing nursery media with organic hydrolized fish fertilizer. We did not observe S. americana forming mycorrhizal associations or parasitizing its own roots (no autoparasitism). Finally, we demonstrated that 1-y-old bareroot plants stored for 3 mo at 4 °C exhibited survival rates that rivaled plants that overwinter outdoors or in the greenhouse.

A new population of federally endangered Schwalbea americana (American chaffseed) was initiated at the state of South Carolina Department of Natural Resources Woods Bay Heritage Preserve, near Turbeville, South Carolina, in 2013–14. Based on improved survival over time, growth to maturity, evidence of reproduction, and size structure similar to that of a nearby natural population, we suggest that the new population has met the initial criteria for success. Persistence and growth of the population will depend on appropriate management in the form of prescribed fire or fire surrogates and, if necessary, continued demographic enhancement in the form of additional plantings.

Single nucleotide polymorphic (SNP) markers were used to characterize the genetic structure of Symphyotrichum georgianum (Alexander) G.L. Nesom, known more commonly as the Georgia aster, from 26 populations across the species' range. This species is considered vulnerable (G3) and was a candidate for listing under the Endangered Species Act. We sampled large (> 500 stems) and small (< 100 stems) populations from across the entire range for the species. Next generation sequencing was used to assess 36 SNP markers for pooled population samples, consisting of equal amounts of genomic DNA from 30 individual stems sampled across each population. Most of the genetic variation was partitioned within and less among populations, which is consistent with perennial outcrossing species. There was a significant (r = 0.506, P < 0.001) positive association between geographic distance and genetic distance among populations, indicating increasing genetic distance (genetic dissimilarity) with increasing geographic distances between populations. There was no statistically significant difference in genetic diversity between large and small populations, but trends were observed. The Georgia and North Carolina large populations were more genetically diverse than the small populations, while the small populations were more genetically diverse than the large populations in Alabama and South Carolina. Symphyotrichum georgianum is an outcrossing perennial aster with a rhizomatous growth habit. Extensive clonal growth could account for the low genetic diversity estimates from large populations; however, quantifying the extent of clonal growth within sites is beyond the scope of the current study. There was no association between genetic diversity measures and seed fill or germination rates. Additional fine scale genetic structure studies are underway to address the extent of clonal growth in these remnant populations and how that may affect viable seed production.

Genetic variation in a single species can have predictable and heritable effects on associated communities and ecosystem processes, however little is known about how genetic variation of a dominant species affects plant community assembly. We characterized the genetic structure of a dominant grass (Sorghastrum nutans) and two subordinate species (Chamaecrista fasciculata, Silphium integrifolium), during the third growing season in grassland communities established with genetically distinct (cultivated varieties or local ecotypes) seed sources of the dominant grasses. There were genetic differences between subordinate species growing in the cultivar versus local ecotype communities, indicating that intraspecific genetic variation in the dominant grasses affected the genetic composition of subordinate species during community assembly. A positive association between genetic diversity of S. nutans, C. fasciculata, and S. integrifolium and species diversity established the role of an intraspecific biotic filter during community assembly. Our results show that intraspecific variation in dominant species can significantly modulate the genetic composition of subordinate species.

Continued loss of coastal wetlands due to anthropogenic causes along the Atlantic and Gulf coasts has increased the need to restore eroded or hardened structures along the shoreline back to natural marsh systems. The source of plant material used in these restoration plantings may have unintended consequences for the reestablishment of marsh systems, especially if the plant material is not adapted to the local environment. In this two-year field study, we tested the hypothesis that locally collected Spartina alterniflora (Smooth Cordgrass) will have higher plant performance than non-local commercially available plant material from native plant nurseries. We found that locally collected S. alterniflora plants had higher survivorship, aboveground biomass, and cumulative stem length than plants from non-local sources. There was a significant association between plant performance and genetic similarity at the end of the first field season. Based on our findings, we recommend the use of locally collec...