Volume 89 – Issue 1 (May 2024) – The Southern Appalachian Botanical Society

2024 Richard and Minnie Award Winners

Editorial Staff
2024-06-20T00:00

The Richard and Minnie Windler Award recognizes the authors of the best systematics and ecology papers published in Castanea during the previous year. For 2024, authors of two articles were selected as winners: Ashley B. Morris, Clayton Visger, Shelby Watkins, and Cathy Pollack for their article, “Extremely Low Levels of Genetic Variation and Predicted Shifts in Suitable Niche Space for a Geographically Disjunct, Federally Endangered Legume, Leafy Prairie-Clover (Dalea foliosa)”
(Castanea 88[1]:91–110), and Michaella Ivey and Lissa M. Leege for their article, “Life After Privet: Plant Community Dynamics in a Forested Wetland Following Removal of the Invasive Ligustrum sinense Lour” (Castanea 88[1]:49–60).

Letter to the Editor

Jeremy D. Rentsch
2024-06-20T00:00

In a Warming World: Sarracenia as a Possible Model for Range Shift Dynamics and Conservation Highlights Need for Additional Population Genomics Research

Investigating Shade Tolerance and Phenotypic Plasticity of Virginia Spiraea (Spiraea virginiana Britton), a Federally Threatened Shrub

Rose P. Dickson
Jonathan L. Horton and Jennifer Rhode Ward
2024-06-20T00:00

Virginia spiraea (Spiraea virginiana Britton, Rosaceae) is a putative shade-intolerant, disturbance-adapted, riparian shrub species native to the southern Appalachian Mountains. This species was listed as threatened in 1990, and a federal recovery plan was developed in 1992. Current reassessment of the recovery plan includes proposals for propagation and out-planting to supplement and restore wild populations. Genotypes with greater shade acclimation would likely have higher survival in natural populations, would require less frequent shade-reduction management, and could be integrated into populations that need restoration. In summer 2022, we examined steady-state (maximum light-saturated photosynthetic, dark respiration rates, quantum yield, light compensation point) and dynamic (photosynthetic induction and loss patterns) photosynthetic characteristics, pigment concentrations, and specific leaf mass of cloned propagules from five elements of occurrence along the South Fork of the New River in Ashe County, North Carolina, along an artificial light gradient (100%, 75%, 50%, and 20% of full sun) in a common garden. Data were compared among light treatments using ANOVA or non-parametric tests. Light treatment had significant effects on maximum photosynthesis, dark respiration, specific leaf mass, and light compensation, but not quantum yield, pigment concentrations, or induction and loss times. Some parameters had plasticity similar to that seen in other woody shrubs, while others were less plastic. A surprising finding was that plants performed better under 75% full sunlight suggesting an ability to tolerate, and maybe even a preference for, partial shade in this species. Future studies should examine photosynthetic characteristics of individuals from genetically contrasting source populations.

Range-Wide Quantitative Habitat Characterization of Critically Imperiled Ludwigia ravenii (Onagraceae)

Mary Rose Conlin
Alexander Krings, William K. Petry, Jodi Forrester, and James Crawford
2024-06-20T00:00

Ludwigia ravenii (G1G2) is a wetland-obligate perennial, endemic to the Atlantic Coastal Plain. The species appears to be relegated to roadside ditches and ruts, and is under review for federal listing. The objectives of this study were to quantitatively assess biotic and abiotic habitat characteristics of extant populations and augment knowledge of the species ecology. Two congeners were selected for comparative analysis: L. alternifolia and L. pilosa. Over two field seasons, data were collected from 108 1 m2 quadrats and variable length transects across the species range. All 17 element occurrences of L. ravenii on record during the 2020–2021 sampling period were visited and 15 (nplots=62) were sampled. Forty-six plots at 14 sites were collectively sampled for the target congeners (L. alternifolia, nplots=27; L. pilosa, nplots=19). Variables assessed included: physical ditch dimensions, aspect, elevation, canopy cover, abiotic and vegetative cover, and edaphic variables (nutrient composition and pH). Data were visualized using NMS and PCA, and analyzed using ANOVA and post-hoc tests. Only PCA showed distinct clustering of quadrats of L. ravenii along soil fertility gradients. Quadrats of L. ravenii exhibited median values compared to congeners in many measured variables, including canopy cover, species richness, and Shannon’s diversity index. Quadrats of L. ravenii differed most strongly from congeners by more acidic mean soil pH (4.68±0.05). Although no single species emerged as an ideal indicator, the combination of L. linearis and Kellochloa verrucosa was found to be highly suggestive of suitable habitat for L. ravenii.

Asian Bittersweet (Celastrus orbiculatus) Occurrence at Coarse and Fine Scales in North Carolina and Virginia

W. Henry McNab
Tracy Roof and Erik C. Berg
2024-06-06T00:00

Asian bittersweet (Celastrus orbiculatus) is a widespread, invasive, twining vine in eastern North American forests. Factors associated with its local occurrence are well known but seldom reported at geographic scales coarser than research locations. We evaluated its occurrence across a hierarchy of land units ranging from coarse (provinces), intermediate (landscapes), and fine (site) scales in North Carolina and Virginia. Chi-square tests indicated a significant difference in the proportion of plots with C. orbiculatus in mountain (5.5%) compared to piedmont (9.9%) provinces. Using groups of forest types (e.g., Acer-Betula, Quercus-Pinus) to represent landscape-scale land units, C. orbiculatus occurred in a greater proportion of plots classified as Quercus-Carya. At the fine scale of sample sites within landscapes, in plots where C. orbiculatus was present the soil moisture regime was classified as mesic significantly more often than xeric in both provinces. Foliage cover differed between mountain (9.6%) and piedmont provinces (5.1%), and among several forest type groups at the landscape scale but responded weakly to moisture regime. Our results show that the proportional occurrence of C. orbiculatus varied significantly among land units at each hierarchical level. We suggest that our land units, defined by physiography, tree communities and soil moisture regime, represent tentative ecosystems that can be included as spatial variables in models to improve predictions of the presence of C. orbiculatus, for example in response to a changing climate.

The Only Effective Pollinators of Guettarda scabra are Nocturnal Hawkmoths: A Re-Examination and Refutation of Earlier Conclusions

María Cleopatra Pimienta
Carlos Ruiz and Suzanne Koptur
2024-05-01T15:50

In south Florida, the rough-leaf velvetseed, Guettarda scabra, is limited to fragments of the endangered pine rockland habitat. Its flowers exhibit traits typically associated with attraction of nocturnal hawkmoths (Sphingidae), although they are abundantly visited by diurnal lepidopterans. These observations question whether the sphingophilous nature of this species represents actual dependence on nocturnal visitors for sexual reproduction. A previous study found diurnal pollination in G. scabra; however, the results may have been skewed by extensive plant manipulations. To address this, we conducted a more comprehensive investigation to re-examine the role of diurnal visitors in the plant’s reproduction. We evaluated the relative contribution of diurnal and nocturnal flower visitors to female reproductive success of G. scabra in its natural habitat. We selectively exposed flowers to these visitor groups and identified all the lepidopteran visitors observed. We found that plants exposed exclusively to nocturnal visitors exhibited significantly higher fruit-set than those only exposed to diurnal visitors, whose fruit-set was minimal and equivalent to that of plants never exposed to visitors. These findings indicate that nocturnal visitors are essential for successful sexual reproduction of G. scabra. Our field observations revealed that at night, flowers of G. scabra are visited by the hawkmoth Xylophanes tersa, suggesting a specialized pollination system in which hawkmoths are effective pollen vectors of this plant. Contrary to earlier conclusions, we demonstrate that flowers of G. scabra are exclusively pollinated by nocturnal moths, despite more frequent legitimate visitation by diurnal lepidopterans, which therefore act as nectar and pollen thieves.

In Search of the “Piedmont Prairies”: Multivariate Analyses of Heliophilic Plant Communities in the Heart of the Piedmont of Eastern North America

Alexandria D. Szakacs
Thomas R. Wentworth and Alexander Krings
2024-04-22T13:15

Although vegetation succession in the Piedmont of eastern North America favors closed-canopy forest in the absence of disturbance, historical evidence suggests upland vegetation of the region was, in near history, characterized by areas of heliophilic vegetation, such as prairies, savannas, and woodlands. While some work has been undertaken to characterize putative remnant communities at the local and subregional level, there has been no comprehensive, quantitative study to characterize the breadth of heliophilic vegetation commonly referred to as “Piedmont prairies” in the mid-Atlantic portion of the Piedmont, despite evidence that more than one community type is likely represented. We fill this gap by assessing Piedmont prairie communities in the present-day landscape using the best quantitative vegetation data currently available from the Carolina Vegetation Survey vegetation-environment database. We extracted records for 195 permanent vegetation plots representative of upland, terrestrial, open or semi-open vegetation in the Piedmont of the Carolinas and Virginia, a region coinciding with 17th- and 18th-century accounts of historical savannas. Through hierarchical clustering (flexible-β) and stride analysis (plotting the PARTANA ratio and silhouette width), we determined the optimal partition for our dataset to be 12 clusters. The R package optpart was used to move plots between clusters to further ensure plots are members of their best-fit cluster. Nonmetric multidimensional scaling ordination was used to visualize compositional trends in the dataset. We identified 12 major types of heliophilic vegetation that can be categorized into five larger groupings: Piedmont Oak-Hickory and Red Cedar Woodlands, Piedmont Glades, Piedmont Pine Woodlands, Piedmont Savannas and Grasslands, and Piedmont River Terrace Glades.

Assessment of Macrolichen Diversity at Ordway-Swisher Biological Station in Northern Florida Contributes to the Scientific Mission of NEON

Laurel Kaminsky
Matthew E. Smith
2024-04-15T17:00

The National Ecological Observatory Network (NEON) is gathering select ecological and taxonomic data across 81 sites in the United States and Puerto Rico. Lichens are one of the organismal groups that NEON has not yet assessed across these sites. Here we sampled lichens at Ordway-Swisher Biological Station (OSBS), a NEON site in north central Florida, to provide a baseline survey of the commonly encountered macrolichens (foliose, fruticose, and squamulose lichens). Macrolichens represent a subset of observable lichens and are more commonly surveyed than crustose lichens. Seventy-four species of macrolichens were collected, including 25 occurrences that constitute new records for Putnam County, Florida. The lichen diversity at OSBS comprised approximately 30% of the macrolichen diversity known from the entire state of Florida. Fifty-four taxa are common in the state of Florida, 12 infrequent across the state, and eight are considered rare. Macrolichens were the seventh most species-rich taxonomic groups at OSBS and more diverse than the NEON focal groups of mammals and fish. Lastly, we suggest a theoretical roadmap for how lichenologists could work together with NEON to include lichens in future datasets. We hope that biologists focused on other key organismal groups will sample in NEON sites so that NEON data can be leveraged appropriately in future cross-taxon studies of biodiversity at the continental scale.

Volume 89 - Issue 1 (May 2024)

Castanea