This is the first documentation of extrafloral nectaries and associated myrmecophytism in Opuntia cespitosa. Three species of ants were observed visiting extrafloral nectaries on O. cespitosa, and two species were observed exhibiting competitive plant-guarding behavior.

The ability of plant species to mitigate environmental stresses is crucial for maintaining their populations and communities. One potential mitigation approach is a growth strategy shift mediated by intraspecific trait variation. We evaluated potential stress-induced shifts in two growth strategies across six common Florida scrub shrub species in two major groups, oaks (Quercus spp., Fagaceae) and heaths (Ericaceae), along an elevational stress gradient. The acquisitive-conservative gradient explains how plants invest in aboveground tissues to photosynthesize more, while the collaboration gradient explains how plants attain belowground resources using a ‘do-it-yourself’ strategy or collaboratively ‘outsourcing’ with mutualistic mycorrhizal fungi. We expected high-stress environments to shift species towards conservative growth with increased symbiont collaboration compared to low-stress environments. For each species, we measured a suite of aboveground (all species) and belowground (oaks only) plant functional traits in two or more different habitats along an elevational stress gradient. Aboveground traits (leaf circularity and stomatal density) significantly decreased with stress across all species analyzed, suggesting a shift to a more conservative strategy. Belowground oak traits showed significant support for a shift to more collaboration with stress, with decreases in specific root length and increases in ectomycorrhizal tip density with stress. Overall, we found that oak and heath shrubs showed limited support for shifting to a conservative strategy with stress and relatively strong support for the oaks to shift to a more collaborative strategy. These findings advance our broader knowledge of how oak and heath species cope with environmental stress via shifting growth strategies.

We examined the genetic basis for the spatial segregation of two different morphotypes within populations of Phacelia bipinnatifida, a biennial plant species associated with cove forest communities of the southern Cumberland Plateau and determined that these morphotypes were actually two distinct species. Given that there are no reported subspecies or varieties in the literature that would conform to these morphotypes, we believe we are the first to describe these morphological and genetic differences. We describe and name Phacelia sewaneensis as a new species that is differentiated from Phacelia bipinnatifida by having purple corollas, longer stamens, basal leaves without gray blotches, and more highly dissected basal leaves. Genetic analyses of individuals from sympatric populations found in three geographically distant locations on the southern Cumberland Plateau revealed that Phacelia sewaneensis (purple morphotype) was more similar genetically to purple morphotypes at the other locations than to sympatric individuals of Phacelia bipinnatifida (blue morphotype). We found that at a given site, the two species occur in large, non-overlapping, yet adjacent patches within a cove, and these patches remain homogeneous (with respect to species) from year to year. Phacelia sewaneensis prefers rocky soils and is found in higher density populations than Phacelia bipinnatifida. We establish a new epitype for Phacelia bipinnatifida and holotype and isotypes for the newly described Phacelia sewaneensis. We discuss why this new species of Phacelia has been missed by botanists, despite its multiple distinguishing features.

Both aquatic flora and Mississippi flora are underrepresented in herbarium collections. This paper reports nine noteworthy collections of 6 aquatic and wetland taxa in Alabama, Arkansas, and Mississippi. These taxa include 5 angiosperms and 1 charophyte. Two of these taxa are introduced to the United States, while the rest are presumed native. Lychnothamnus barbatus, Utricularia tenuicaulis, and Vallisneria × pseudorosulata are new to the flora of Mississippi and Cyperus blepharoleptos is new to the flora of Arkansas.

There is limited information on Sarracenia jonesii, a federally endangered and critically imperiled carnivorous plant. This study provides insight into how soil nutrient status affects this pitcher plant's ability to grow carnivorous leaves and catch its own prey, as well as how it affects the plant's ability to flower and reproduce. Sarracenia jonesii clumps produce more flowers as the number of carnivorous leaves increases. The soil nutrient assessment of this population demonstrated that these carnivorous plants can occupy soil that has high nutrient content potential but low plant-available nutrients, specifically nitrogen. Flowering and the presence of soil ammonium (NH4) did not exhibit a relationship. The growth of non-carnivorous leaves, phyllodia, and the presence of soil NH4 also did not show a significant relationship. A historical assessment of one of the few remaining populations of S. jonesii showed a decline in clumps but showed increased leaf and flower production. This can inform future conservation strategies to ensure plants are propagated and planted in appropriate soil conditions for ideal growth, carnivory, and reproduction.

American chestnut (Castanea dentata), once a dominant canopy species in eastern North America, succumbed to invasive pathogens in the early 20th century. The American Chestnut Foundation attempts to breed pathogen resistance using backcrossed hybrids with Chinese chestnut (Castanea mollissima ). We compared steady-state photosynthetic characteristics among backcrossed chestnut hybrids (BC1F1 with 3/4 American genotype and BC3F3 with 15/16 American genotype) and pure American chestnut. Photosynthetic capacity was compared among these three chestnut classes with steady-state light response curves. Dark respiration rates, quantum yield, and maximum photosynthetic rates differed among these chestnut types, but light compensation point, a measure of shade tolerance, did not. In July and August, we measured plant water potential (at predawn, morning and afternoon) and leaf gas exchange (morning and afternoon) under ambient conditions between the 15/16 and 3/4 AC hybrids. Trees in the pure American chestnut population suffered blight-induced dieback resulting in shrubby plants that differed in size and light environment, so these were not used in diurnal comparisons. Despite similarities in soil moisture and pre-dawn water potential, there were significant differences in daily gas exchange and water potential. Trees in the 15/16 American chestnut population generally had higher gas exchange rates in the afternoon, while also experiencing lower plant water potential and a greater diurnal change in water potential. These results suggest that these trees may be better able to perform under moderate atmospherically-induced water stress than trees in the 3/4 American chestnut population. Quantifying relationships between water relations, gas exchange, and environmental factors allow evaluation of long-term performance and may better inform site selection and management practices.

Spiraea virginiana Britton (Virginia spiraea), a threatened riparian shrub whose range extends through the Appalachian and Blue Ridge Mountains, reproduces primarily asexually. Successful seed production is rare under field conditions, but the relative contributions of intrinsic factors and pollinators are unclear. Open, selfed, inbred, and outbred pollination treatments were applied to populations of S. virginiana from three western North Carolina drainages, and stigmas from open pollinated treatments were collected to quantify pollen loads under light microscopy. While viable pollen production was high, seed set was low under both open and hand-pollinated treatments and was not correlated with pollen load. Pollen:ovule ratios suggested a generalist pollination syndrome, as did pollen loads on abundant floral visitors. Thus, rather than pollen limitation, reproductive success could be limited by factors like depressed genetic diversity among populations. Microsatellite analysis was used to assess population genetic patterns across the species' range. Spiraea virginiana demonstrated high heterozygosity and little genetic structuring, and frequency of clones was high. In addition, polyploid individuals were found at all sites, and potential mixing of ploidies within populations might also limit sexual reproduction. Management steps should be taken to allow this clonal species to continue successful rhizomatous growth and fragmentation. In addition, restoration work should consider the lack of genetic structure when choosing appropriate vegetative propagules for out-planting, understanding that the goal of augmentation is to increase genetic diversity via sexual reproduction, which is uncommon is Virginia Spiraea.