Current Issue (87-1)

Dendrochronological Reconstruction of the Historical Invasion of Balsam Woolly Adelgid, Adelges piceae, Feeding on Canaan Fir, Abies balsamea subsp. phanerolepis in the Central Appalachian Mountains

During biological invasions, the initial arrival and establishment of invading populations often go unnoticed for many years yet information on early invasion dynamics is key to understanding and managing invasions. We used the presence of ring discoloration, “rotholz”, in tree cores to date historical Adelges piceae outbreaks and reconstruct its invasion history in 14 Abies balsamea subsp. phanerolepis stands in West Virginia. In 2018, we collected and cross-dated tree ring samples from 676 cores. We measured ring width increments and recorded the presence of rotholz in each annually dated ring. Rotholz was present in tree cores sampled from each of the 14 study sites, with the first rotholz occurrence in 1952 and widespread evidence of rotholz as early as the 1980s. Time series of rotholz frequencies indicate two synchronized waves of elevated rotholz frequencies that were observed at most sites from 1998 to 2003 and again from 2006 to 2013, coincident with observed outbreaks. Unlike patterns of growth suppression found among trees affected by defoliating insects, we observed a significant and positive relationship between rotholz frequency and standardized growth increment. This relationship is consistent with earlier observations of abnormal growth among trees infested by A. piceae. Our samples of rotholz frequencies suggests that rotholz may be a better indicator of past outbreaks of A. piceae than growth. The presence of A. piceae and its role in hastening decline of these rare relic tree populations would lend support to increased attention for the search for A. piceae biological control agents to limit damage by this insect.

Ecological Correlates of Reproductive Output in a Tennessee Population of Short’s Bladderpod, Physaria globosa (Brassicaceae)

Physaria globosa (Brassicaceae), commonly known as Short’s Bladderpod, is a federally protected species restricted to Tennessee, Kentucky, and southern Indiana. In 2016, we studied aspects of life history and ecology in a population of P. globosa near Hartsville, Tennessee. Our objectives were to document fecundity-related life history traits and to examine the potential influence of light levels and soil depth on plant growth and reproductive output. In addition, we examined 45 herbarium specimens of P. globosa to assess the potential relationship between taproot size and number of inflorescences per plant. We found the strongest positive relationships between the number of flowering stems per plant and the number of flowers and fruits per plant. Relationships between light levels, soil depth, and biotic factors were only weakly significant. Taproot width was positively correlated with the number of flowering stems on herbarium specimens. Our findings increase the life history and ecology knowledge base available to guide ongoing recovery efforts for the species.

The Effects of Varying Nutrient Availability on Females and Hermaphrodites of the Gynodioecious Geranium maculatum

Sexual dimorphism in plant growth and/or reproductive responses to the surrounding environment has been documented in some plant species. In gynodioecious plants, it is especially important to understand whether females and hermaphrodites differ in their response to environmental stressors, as the fitness of females relative to hermaphrodites determines the extent to which these separate sexes are maintained in natural populations. Soil nutrient availability is of particular importance given the different nutrient requirements of male and female sexual functions in plants. Here, we evaluated and compared the growth of females and hermaphrodites of Geranium maculatum in response to varying levels of nutrients. Using a greenhouse experiment, we manipulated the overall nutrient, nitrogen, and phosphorus levels in the soil and measured growth, allocation, and leaf quality responses in both females and hermaphrodites. We found that the sexes responded similarly in their growth and allocation responses to nutrient availability, despite evidence that female leaf chlorophyll content may have increased more than that of hermaphrodites across soil nitrogen levels. Our findings demonstrate that while hermaphrodites may differ from females in terms of their physiological response to varying nutrient levels, these slight physiological differences do not translate into meaningful growth differences.

Community Science Success for Herbarium Transcription in Arkansas: Building a Network of Students and Volunteers for Notes from Nature

An estimated 390 million herbarium specimens worldwide provide data for scientific study, but specimen labels must be transcribed into standardized databases to be readily useable by the scientific community. Yet, data entry cannot be completed with current staffing and funding. Notes from Nature provides an infrastructure for community science transcription of natural history specimen labels with tutorials and a platform for communication among community scientists and researchers. The Plants of Arkansas project, now led by the Arkansas Natural Heritage Commission, built an active transcription community by coordinating local universities, recruiting service organizations, and engaging worldwide users online. Training members of service organizations creates continuing users dedicated to the project, and students learn about natural history collections and community science through real-world assignments. Our goals are to: 1) enumerate participants and transcription of the first 3.5 years of the project, 2) describe in-person events for recruitment, training, and connection with local collections, and 3) propose recommendations based on the evidence that increased engagement results in increased rates of contribution. The distribution of transcriptions per user compares to other community science projects, with a few individuals who transcribe thousands of labels. However, we have had more users that contribute >50 transcriptions in the Plants of Arkansas project. With our project’s success, we offer suggestions to manage a transcription community and advance the rate of specimen digitization worldwide.

Noteworthy Collections: First documented antheridia on Palamocladium leskeoides (Brachytheciaceae) in North America

The collection reported here of Palamocladium leskeoides, made in Tennessee, represents the first documented observation of antheridia on this species in North America. Palamocladium leskeoides is a dioicous moss species with a pantropical distribution. Uncommon in the United States, it grows in disjunct populations in moist habitats on calcareous rock. We visited Rock Island State Park (Warren County, Tennessee) in 2019 and relocated a population of this species that was last collected from that location in 1979. Two small voucher specimens were collected and one was observed to have a perigonium containing antheridia attached to the stem. The invasive evergreen Euonymus fortunei was also observed covering surfaces that could otherwise be suitable habitat for P. leskeoides. We plan to assist Rock Island State Park with remediation of invasive plants to improve the available habitat and monitoring the population of this rare moss.

Clarifying Taxonomic Boundaries in Nuphar sagittifolia (Nymphaeaceae): Insights from Morphology and Population Genetic Diversity

Nuphar sagittifolia (Nymphaeaceae), Cape Fear spatterdock, is an aquatic macrophyte endemic to the Atlantic Coastal Plain and of conservation concern in North Carolina, South Carolina, and Virginia in the United States. The existence of populations of unclear taxonomic identity has precluded assessment of the number of populations, distribution, and conservation needs of N. sagittifolia. The circumscription of the species was re-assessed using morphological and genetic analyses. Approximately 30 individuals from each of 21 populations of Nuphar across the N. sagittifolia range were included in genetic and morphological analyses, along with the type populations for three taxa. Genetic diversity was assessed by genotyping individuals across 26 SNP loci identified for this study, and morphological variation was assessed through measurement of 31 leaf, flower, and fruit characters. STRUCTURE analysis identified three genetic groups with corresponding morphological differences in the N. sagittifolia range: N. sagittifolia, N. advena subsp. advena, and a third group in the Chowan-Roanoke River drainage that requires further study. A revised key based on Classification and Regression Tree (CART) and Bayesian analyses identifies N. sagittifolia based on a leaf sinus-to-leaf length ratio <0.22, leaves not emergent, and leaf length-to-width ratio usually greater than 2.4. Genetic analyses within the N. sagittifolia group as indicated by the revised key indicated relatively low clonality, low gene flow, and low allelic differentiation among populations. Observed heterozygosity was higher than expected heterozygosity in all populations, an observation consistent with a combination of limited clonal reproduction and sexual reproduction resulting in long-lived genets.

Effects of Grassy Bald Management on Plant Community Composition within The Roan Mountain Massif

Within the Roan Mountain massif in the southern Appalachian Mountains, grassy balds are important, yet threatened ecosystems dominated by native graminoids with many endemic and endangered species. Restoration efforts have been conducted for 30 years by several agencies. In 1987–1988 a vegetation analysis was conducted on these balds to characterize plant communities before intensive management began. In summer 2020, we resurveyed the vegetation using similar methodologies on Round, Jane, and part of Grassy Ridge Balds to assess the impact of management activities. Percent coverage of vegetation type was recorded in 226 one m2 plots along 11 transects. Management history was compiled for individual plots. Percent cover data were subjected to cluster analysis, principal components analysis (PCA), non-metric multidimensional scaling (NMS), and regression. Cluster analysis of sampled plots revealed 12 plant community groups. PCA revealed plots separating along a gradient of blackberry and grass cover, as well as blackberry, grass, and fern cover. Results from NMS showed less separation of plots compared to PCA with most plots clustering in the center, except those with high bare ground coverage. A significant positive relationship was seen between graminoid cover and management frequency and a negative relationship with the amount of time since management activity. All of the relationships had low explanatory power suggesting that other factors might influence the plant populations. Our research shows there is a positive association with graminoid cover and increased management frequency, but more research involving other biotic and abiotic factors and management history should be explored.

Two Coastal Plain Dichanthelium (Poaceae: Paniceae) Disjunct in Tennessee Grasslands and Their Conservation

Dichanthelium wrightianum, a species of panic grass whose North American range is exclusive to the Coastal Plain, is reported from Tennessee for the first time. A single population of this species was discovered in a wet grassland remnant in the Eastern Highland Rim physiographic region alongside many other species disjunct from the Coastal Plain. Another Coastal Plain Dichanthelium, D. roanokense, was found at a second wet grassland nearby. While D. roanokense was previously reported for Tennessee, it has not been recently documented or confirmed to be extant within the state and its current status should be reviewed. The ecology and conservation of Tennessee populations of both species are discussed.

Determinants of Population Genetic Structure in Chamaecrista fasciculata (Michx.) Greene (Fabaceae) in the Southeastern United States

Chamaecrista fasciculata is a widely distributed, phenotypically variable species in the eastern U.S. Whereas studies have demonstrated genetic structure and local adaptation in northern areas of its distribution, there has been no comparison of genetic variability among populations at the southern extent where phenotypic variation is more complex. We characterized genetic variation at 14 microsatellite loci for populations in Mississippi and Alabama and compared this to variation in a phenotypic trait, leaf pubescence. Geographic distance, climatic variables, and elevation were evaluated as factors to explain the observed patterns of genetic diversity. A significant amount of variation (19%) resided among populations, but most variation (68%) was among individuals. Assignment of individuals into genetic groups suggests two primary clusters, but these groups are not concordant with known geographical or ecological breaks, nor phenotypic variants. Genetic structure at a regional scale can be characterized as isolation by distance, while environmental factors may play a secondary role in limiting gene flow at local scales. Mean population FST is strongly associated with allelic diversity and heterozygosity, suggesting that genetic drift influences population variation. Despite the presence of genetic and phenotypic variation in southern populations of C. fasciculata, the lack of concordant patterns between these types of variation indicate that they are not driven by the same factors. This study demonstrates how local factors differentially influence the maintenance of intraspecific variation and suggest the southern distributional range is an active area of evolution for C. fasciculata.