To evaluate the floristic sustainability of three small, isolated tallgrass prairie remnants, spatial and temporal patterns of species and functional group (FG) composition, richness, diversity, and dominance were examined to determine whether there was divergence between edge (outer 10 m) and interior zones. These remnants, all protected and managed nature preserves, are rectangular in shape and range in area from 1.29 ha to 1.77 ha; each is bordered by cropland and unmanaged or mowed ruderal grassland. A stratified sampling design was established using permanently marked transects oriented perpendicular to the long axis of each site. Vegetation data were collected in 50 cm × 50 cm quadrats along each transect; prairies were resampled 5–6 yr following baseline data collection. The null expectations were no differences between edge and interior zones, no differences between edge type (crop and noncrop), and no change over time. Results from linear mixed-effects models identified significant differences between edge and interior zones for native species density, native diversity, dominance, percent native cover, and measures of floristic quality; however, there were no time differences and no significant zone × time interactions. Distance from edge to peak levels of species density and diversity was about 15 m yielding core habitats 43% to 50% of remnant size. Beta diversity based on species presence was greater in edge zones compared to interior zones, and declined slightly in repeated samples. Functional group diversity was lower in edge zones compared to interior zones and declined significantly in the repeated samples. Functional groups with significant affiliation to the edge zone were nonnative grasses, woody vines, ferns/allies, and nonnative legumes; FGs affiliated with the interior zone were C₄ grasses, hemiparasites, nitrogen-fixing shrubs, and perennial forbs. One site was sampled three times following 5–6 yr intervals and there were no additional within-site differences in the third sample. These prairies support a rich diversity of native species; however, patterns suggest they are effectively smaller than they appear with a trend of declining functional diversity.

We investigated an old-growth oak-shortleaf pine (Pinus echinata) stand of high ecological integrity in east-central Oklahoma located west of the continuous native distribution of shortleaf pine. With the exception of an abundance of shortleaf pine, the basal area (17.2 m²/ha), density (559.6 trees/ha), and species composition of this unmanaged stand is similar to other old hardwood forests in the Cross Timbers ecoregion. Tree-ring dating indicates that the oldest post oak (Quercus stellata) and shortleaf pine sampled in Shortleaf Canyon were 262 and 230 yr old, respectively. Dendrochronology indicated that drought-related disturbances contributed to several episodic pulses of natural regeneration of shortleaf pine at this site. Coupled with local historical documentation and regional paleoecological evidence, the absence of older pines at this isolated site suggests that P. echinata may have naturally colonized Shortleaf Canyon recently, perhaps during the last 250 yr.

Human-caused decreased fire frequency allows a shift toward woody vegetation in North American grasslands. Since the 1960s, Midwest hill prairies have declined in area due to invasion by Juniperus virginiana L. (eastern redcedar) and encroachment of deciduous woody vegetation. This process has been thought to result from reduced fire frequency but supportive data have not been available. We used tree-ring analysis of J. virginiana to develop chronologies of tree growth and fire scars since the mid-1800s at Fults Hill Prairie Nature Preserve, Monroe County, IL, and used them to understand effects of historical climate and changing fire regimes on loss of prairie habitat. Tree-ring analysis indicated spread of J. virginiana from escarpment habitat into prairie after 1960. Linear regression of time series data from aerial photos projected 80–100% loss of prairie cover before the year 2040. The J. virginiana fire scar chronology revealed a < 2-yr median fire return interval between 1850 and 1959. The percentage of scarred trees (a proxy for fire severity) was greater before 1900, and fire years corresponded to drought years during this period. After 1900, railroad development probably increased local ignitions and spread of fire, decoupling fire from drought. After 1960, J. virginiana invasion and loss of prairie area corresponded to a 5-yr median fire interval as well as increased human population density and loss of railroad ignitions. These changes suggest that hill prairies are highly fire-dependent, and that decoupling from climatic control of their fire regime and reduced fire frequency caused by changing human land use are contributing to their decline. They are also apparently prone to woody invasion due to proximate sources of trees. Juniperus virginiana establishment in prairie followed a 2-yr median fire return interval, and their survival increases with time since fire. As with more mesic eastern grasslands, a < 3-yr fire return interval may be needed to maintain hill prairie vegetation. Restoration of woody vegetation–invaded hill prairies may require supplementary management.

Occurrence of plant pathogens and levels of disease are modified by variations in the abiotic and biotic environment. However, there is little information on the effects of environmental changes at a local scale on incidence and severity of foliar disease in seasonal tropical natural systems. We studied the occurrence of leaf fungal diseases in four tree species from a Mexican seasonal tropical dry forest over 2 yr and explored its relation with abiotic factors. Necrotic leaf spots affected all plant species. The probability of disease incidence tended to be higher in the year 2008 than in 2007, and varied among surveyed sites. Mean proportion of leaf area damaged per plant varied among sites. In all the cases where the relationship was significant, the probability of disease incidence and leaf area damaged per plant were negatively affected by canopy openness and mean maximum temperature. Only in Achatocarpus gracilis was the probability of disease incidence positively affected by relative humidity in both years, and the leaf area damaged per plant was only positively affected by this variable in 2007. Our study contributes to the understanding of the role of abiotic factors in the occurrence and severity of diseases in seasonal tropical dry forests.

Understanding plant reproductive traits is important to discerning underlying mechanisms of patch formation by clonal plants after soil disturbance. Reproductive traits that are likely important to patch formation include regeneration ability of rhizomes, seed production and long-term germination ability, and seed presence in the seedbank. In this study, reproductive traits of the clonal plant Lachnanthes caroliniana (Lam.) Dandy that were dominating patches disturbed by feral swine were assessed. The study assessed the ability of rhizomes to resprout in relation to rhizome size (10 cm to 20 cm or 20 cm to 30 cm) and burial depth (buried or surficial). Field surveys were conducted in monocultures to measure the density of inflorescences and seed production. A seed germination and longevity growth chamber experiment was conducted to test the effect of moist or submersed conditions. Finally, a seed bank assay measured the field germination ability of L. caroliniana. Rhizomes had, on average, 81% survival rate and 100% buried rhizomes; rhizome size did not affect survival. Seed production was high with 126,579 seeds per m², but in the growth chamber germination was low (0.5%) and short-lived, with nearly all germinates occurring by 51 days and one germinant at 129 days. Only one seedling of L. caroliniana germinated from the seed bank of soil collected prior to the current year's seed rain, also supporting a short-lived seed bank, as suggested by the timeline of the seed germination study results. These results suggest that reproductive traits of rhizome resprouting and high production of seeds (approx. 600 germinants per m²) may give this species a competitive advantage to form dense patches following feral swine rooting disturbance. Since feral swine continuously return to patches of L. caroliniana, it is likely that this plant and other disturbance-adapted clonal species could increase at the landscape scale as feral swine populations continue to rapidly expand.

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.

Species delimitation in foliose macrolichens has long been dominated by chemotaxonomy, resulting in many examples of seemingly morphologically identical species that differ only in the secondary metabolites they produce. This study examines two such species that are widespread in southeastern North America: Parmotrema madagascariaceum (Hue) Hale and Parmotrema xanthinum (Müll. Arg.) Hale. Drawing on data from biogeography, chemistry, morphology, and molecular phylogenetic analyses of nuclear ribosomal internal transcribed spacer sequence data, the two species are treated as conspecific. A taxonomic treatment is presented along with a discussion of previous studies that have examined the delimitation of species that differ only in the presence or absence of compounds that are accessories in addition to a primary set of substances present in both species.

Trichome diversity in vegetative and reproductive structures of species from the subtribe Leiboldiinae (Vernonieae, Asteraceae) are described and illustrated. Based on scanning electron microscopy, we identified two main trichome types, glandular and eglandular. The eglandular trichomes were further subdivided into unicellular (papillae, conical, and filiform) and multicellular (flagelliform, uniseriate with three variants in the apical cell, and twin hairs). Additionally, the latter showed variation in the number of basal cells, which is most likely related to the type of structure supporting those cells. A species identification key, based on trichome diversity, is provided. We discuss the taxonomic importance of trichomes for delimiting of closely related species and as generic diagnostic characters. In the first case, the presence of glands on the cypsela was a diagnostic character of Leiboldia, and in the second case, the presence of twin hairs on the cypsela and phyllaries of Leiboldia guerreroana differentiates it from Leiboldia serrata.

Shoot apical meristems produce stem tissues, produce leaves, and produce flowers. Cell proliferation characteristics of meristems are dependent upon cell maturation processes and the functions of newly formed cells. Cells of stem terminals depend upon water availability from other plant portions. Inadequate moisture availability to stem terminals reduces shoot growth rates and leaf production rates. Xylem conductivity measurements of terminal shoot meristems and small leaves were approximated using the Hagen-Poiseuille equation to determine relationships between xylem contributions to leaves versus xylem conductivity within stems. Analyses of petiole and stem xylem conductivities for the 23 herbaceous plant species were confined to stem terminals that only had primary xylem cells in stems and only five leaves or leaf pairs. Among stem segments (10 mm to 64 mm in length) among species, the largest leaf areas ranged from 2.34 cm² to 54 cm², stem diameters ranged from 0.82 mm to 3.83 mm, and maximum leaf petiole and stem xylem conductivities were 0.12 g cm MPa⁻¹ s⁻¹ and 0.35 g cm MPa⁻¹ s⁻¹, respectively. For pooled samples, petiole xylem conductivity was well scaled with leaf area of largest leaves (r² = 0.76). For pooled samples, stem conductivity was well scaled with cumulative petiole conductivities (r² = 0.94). When the largest diameter stem sections from each species were considered, stem xylem conductivity was well scaled with mean radius of conduits (r² = 0.82). Overall, stem xylem conductivities were strongly linked to petiole conductivities as leaves developed. Petiole xylem conductivity was well scaled with stem conductivities for all 23 species with markedly different leaf areas.

This paper documents the colonization of the roots of Celastrus orbiculatus by endomycorrhizal fungi in field-collected specimens in New England. The presence of endomycorrhizal fungi in the roots of C. orbiculatus in its introduced range may assist this species in its successful colonization of new habitats.

Bonamia chontalensis Carranza sp. nov. is described and illustrated as a new species from the south of Oaxaca, Mexico. It is a rare plant, known only from a few collections in coastal areas. The species differs from other bonamias by evident unequal, suborbicular external and ovate to long-ovate internal sepals. Possible relations with other species and an identification key for the Mexican species are discussed and provided.

Vismia atlantica, a new species endemic to the central region of the Brazilian Atlantic Forest, is described and illustrated. Collections of this species were initially identified as Vismia latifolia (probably because of a misinterpretation by Reichardt in Flora brasiliensis) and, more recently, as Vismia macrophylla. Vismia atlantica is part of a group of species having large leaves with numerous secondary veins and persistent stamens on the berries, features also present in the Amazonian species Vismia sandwithii.