Domesticated tree species represent an economically and ecologically important group of taxa. Trees differ from other well-studied crop systems (rice, wheat, corn, sunflower) in several basic biological attributes, all of which influence the way in which genetic variation is structured in these organisms. The goals of this study were to delimit a lineage of a Mesoamerican domesticated tree, Spondias purpurea, and to investigate the relationship between this lineage and another sympatric congener (S. mombin) using nuclear and chloroplast sequence data. The fourth intron of Pepc was sequenced for sixty-eight Central American Spondias trees including twelve S. mombin accessions, 55 S. purpurea trees, and one S. radlkoferi individual. Data were analyzed using traditional phylogenetic techniques and using a network approach. Nuclear data were compared with previously published sequence data from the chloroplast spacer trnS-trnG, revealing that the Spondias purpurea lineage includes both cultivated and wild populations, but in localized areas hybridization and incomplete lineage sorting blur the boundaries between the crop species and a sympatric congener. This study provides insight into the nature of a domesticated tree lineage, which, in the case of Spondias purpurea, is generally distinct despite some evidence for ongoing gene flow.

Previous research has shown that identical scale and bark injuries occur on stems of 16 species of columnar cacti in North and South America. For all 16 species, areas with scale and bark injuries on stems were greater on equatorial-facing surfaces than on polar-facing surfaces. Moreover, percentages of stem areas with injuries were well correlated with relative amounts of annual sunlight exposure. Cacti with high levels of scale and bark injuries had high levels of mortality. Previous data have shown that at the Equator, about 1.4 times more incident light occurs on west-facing and east-facing surfaces (equatorial surfaces) than on north-facing and south-facing (polar-facing) surfaces. Herein we determined the percentages of stem areas with scale and bark injuries on equatorial-facing (east and west) and polar-facing (north and south) surfaces of four species of columnar cacti in Ecuador (near the Equator). Specifically, percentages of trough areas with scale and bark injuries were determined for stems of Armatocereus cartwrightianus, Pilosocereus lanuginosus, and Praecereus euchlorus on mainland Ecuador and for Jasminocereus thousarii on the Galapagos Islands, Ecuador. For our analysis, data from all four cactus species were pooled. Chi-square tests showed that average injuries on equatorial surfaces were greater than average injuries on polar surfaces. For the pooled data, injuries on equatorial-facing surfaces were 1.4 times greater than on polar-facing surfaces. Therefore, the 1.4 times greater injuries on equatorial-facing surfaces compared with polar-facing surfaces was coincident with the 1.4 times greater incident light on equatorial surfaces than on polar surfaces for cacti at the Equator. Taken together with previous data, the data of this study show that at least 20 species of long-lived columnar cactus species in the Americas have almost identical scale and bark injuries even though they exist from 32° N to 32° S. Ratios of equatorial vs. polar injuries are well correlated with ratios of PAR (photosynthetically active radiation) for equatorial and polar surfaces. Moreover, the ratio of injuries on equatorial vs. polar surfaces were highly correlated with the latitudes of this study.

Stems in Sesuvium portulacastrum L. (Aizoaceae) increase in thickness by forming successive rings of cambia that formed concentric rings of xylem alternating with phloem. The cambium is semi-storied and exclusively composed of vertically elongated fusiform initials while cambial rays were absent in the early part of the secondary growth. In the older stems some of the fusiform cambial cells undergo further division and develop into vertically upright rays. The first ring of cambium formed thick walled lignified elements centripetally and phloem centrifugally for a definite period. A second ring of cambium is developed from axial parenchyma cells located outside the phloem produced by the previous cambium. Prior to the complete differentiation of new cambial ring, these parenchyma cells divide bi-directionally to form additional parenchyma cells (referred here as secondary cortex) to the outer and inner side. Cells formed outside to the new ring formed secondary cortex, which served as a site for the future cambium. Inner cells differentiated later on into conjunctive tissue between two successive rings. In the newly formed cambium, alternate small segments of the cambium gave rise to conducting elements of xylem towards the center and phloem towards the periphery while the other segments formed thin walled parenchyma on both the sides. Secondary xylem was composed of vessel elements, fiber tracheids and libriform fibers with nuclei whereas secondary phloem consisted of sieve tube elements, companion cells and parenchyma with no rays in the young stem.

Knowledge on seed bank longevity is especially important in understanding population dynamics of invasive species and critical in determining the intensity and length of control efforts. In this study we determined the soil seed bank longevity of Paederia foetida across three main natural habitats that P. foetida occur in Florida (the interior of a mixed mesic forest, a forest edge, and an open grassland). A native of eastern Asia, P. foetida is invasive in natural and human created habitats in the southern United States and Hawaii. We placed multiple bags with known number of fruits (diaspores) in four stations on the soil surface in each habitat and retrieved the bags once a year for three years. Our data demonstrated that P. foetida forms a short term persistent seed bank and seeds may remain viable for more than one year in the soil seed bank. The decline of soil seed bank was significantly slower in the forest interior than in forest margin and grassland. In the forest interior, 38% of the seeds remained viable for one year, but only 2% remained viable in the forest edge and open grassland habitats. The percentages of viable seeds dropped to 4.7%, 0.4%, and 0% after two years in the soil seed banks in the forest interior, the forest edge, and the open habitat, respectively. After three years, only 0.3%, 0.1%, and 0% of seeds were found viable in these three habitats, respectively. Even though very small proportions of seeds survived three years, given that the annual fruit production of P. foetida is typically large and that it only takes a minimum of two viable seeds to start a new reproducing population for this self-incompatible species, we recommend post adult plant elimination monitoring for two years in open habitat, but up to four years in forest areas.

Montane rain forests in Central and South America are threatened by human activities and climate change. Consequently, epiphytic plant genera such as Restrepia are also endangered, making their ex-situ conservation vital. For success, this conservation strategy requires affordable, efficient, and reliable protocols for axenic seed germination as well as protocorm and seedling development prior to establishment ex vitro. In our study, effects of four asymbiotic media (Murashige and Skooge, Phytotech P668, Vacin and Went, and Western) on seed germination and early protocorm development of Restrepia brachypus were compared. In addition, their effects with and without banana pulp were examined on in vitro seedling development. Western medium produced the highest mean germination rate (53%), the second highest mean protocorm diameter (325 µm) and, with banana, the largest mean seedling length (3.6 mm). These data provide a simple protocol using commercially available media that is suitable for ex-situ conservation of Restrepia. These media may also be of use for the micropropagation and conservation of other related orchid genera.

We document a decrease in abundance of Cornus florida due to dogwood anthracnose over a ten year period in upland forest of southern Illinois. Ninety seven permanently marked 0.04 ha plots were sampled in 1994 and 2004 in LaRue Pine Hills/Otter Pond Research Natural Area (RNA) in Southern Illinois. Topographic site characteristics measured were slope aspect, position, angle, elevation, terrain shape, landform, and topographical shading indices. Abundance measurements were tree basal area, tree density, sapling density, and seedling density. The abundance of C. florida and co-occurring woody species were quantified in five overstory dominance types including Pinus echinata/Quercus velutina, Quercus velutina, Quercus alba/Quercus species, Quercus rubra, and Mixed Mesophytes. Between 1994 and 2004, the total tree basal area increased by 7.5% while tree density decreased by almost 20%. The overall composition of the tree and seedling layers did not change significantly, but the sapling layer showed a significant change in composition. The greatest change was the decrease in density of Cornus florida by 54% in the tree and seedling layers and 78% in the sapling layer. The greatest decrease in C. florida density was on mesic sites with low slope position and high topographic shading. The decrease in C. florida was likely due to Discula destructiva, the fungal pathogen that causes dogwood anthracnose. Increases in Asimina triloba and Sassafras albidum saplings, and seedlings of Acer rubrum, Liriodendron tulipifera, Ostrya virginiana, and Sassafras albidum along with decreased seedling density of Quercus alba suggests that the loss of C. florida may lead to future shifts in the composition of these forests.

Removal of canopy dominant trees in temperate closed-canopy forests due to natural or anthropogenic disturbance may allow for the release of co-dominant and sub-canopy trees into the canopy. Historical growth releases of these trees can be reconstructed from the analysis of their annual rings and compared with historical disturbance events to better understand forest dynamics. We applied boundary-line growth patterns, a method for the reconstruction of historical release from disturbance, to annual-ring series of co-dominant longleaf pine in two closed-canopy successional forest sites (Everwoods and Seacock Swamp) the Mid-Atlantic Coastal Plain of southeastern Virginia. The somewhat degraded stands were co-dominated by mixed hardwoods and loblolly pine (Pinus taeda L.) after a long fire-free history. Our study documented recruitment patterns through age-class distribution and reconstructed disturbance events (growth releases) using a modified version of the boundary-line growth method. Ages for all cored individuals at Everwoods (n  =  37) ranged from 32–184 years (x¯  =  53 years), and at Seacock Swamp (n  =  32), from 56–175 years (x¯  =  94 years). Longleaf pine has failed to recruit over the past two decades at Everwoods, and over the past half-century at Seacock Swamp, probably due to increased competition and habitat decline in the absence of fire. Boundary-line growth patterns revealed moderate and major release events for longleaf pines at both sites that we linked to anthropogenic disturbances, such as silvicultural operations (1900s to the 1930s) at both sites and logging by the landowner (early 1950s) at Seacock Swamp. We interpreted extremely low growth rates and dramatic growth-change pulses after disturbance as evidence of heavy suppression atypical for this species, which has been conceptualized as shade-intolerant. Our findings fit with other studies that have suggested that longleaf pine may be less shade-tolerant than formerly thought, at least in some areas or sites. Applications of the boundary-line growth patterns method to old-growth and second-growth longleaf pine forests throughout the southeastern U.S. could help to document possible spatial variability in disturbance histories, responses to releases, and suppression patterns.

The 1998 ice storm, which impacted many parts of eastern Canada and the northeastern United States, resulted in significant damage to forests. The intensity of the damage was quite variable both between stands and between individual trees. Using visual assessment of tree crown health and dendrochronological techniques we examined the response to the ice storm of sugar maple (Acer saccharum Marsh.) dominated forests in Gatineau Park, Quebec. Crown health assessment indicated that most of the heavily damaged trees showed some recovery in the years following the ice storm. However, dendrochronological analysis of the dominant sugar maples suggested that the most damaged individuals had still not returned to pre-ice storm stem growth levels six years following the ice storm. Combined, the crown health and dendrochronological analyses suggest that following the storm, in heavily damaged trees, resources were allocated to crown foliage production on remaining branches at the expense of stem growth.

Abiotic factors, particularly area, and biotic factors play important roles in determining species richness of continental islands such as cedar glades. We examined the relationship between environmental parameters and species richness on glades and the influence of native species richness on exotic invasion. Field surveys of vascular plants on 40 cedar glades in Rutherford County, Tennessee were conducted during the 2001–2003 growing seasons. Glades were geo-referenced to obtain area, perimeter, distance from autotour road, and degree of isolation. Amount of disturbance also was recorded. Two-hundred thirty two taxa were found with Andropogon virginicus, Croton monanthogynus, Juniperus virginiana, Panicum flexile, and Ulmus alata present on all glades. The exotics Ligustrum sinense, Leucanthemum vulgare, and Taraxacum officinale occurred on the majority of glades. Lobelia appendiculata var. gattingeri, Leavenworthia stylosa, and Pediomelum subacaule were the most frequent endemics. Richness of native, exotic and endemic species increased with increasing area and perimeter and decreased with increasing isolation (P ≤ 0.03); richness was unrelated to distance to road (P ≥ 0.20). Perimeter explained a greater amount of variation than area for native and exotic species, whereas area accounted for greater variation for endemic species. Slope of the relationship between area and total richness (0.17) was within the range reported for continental islands. Disturbed glades contained a higher number of exotic and native species than nondisturbed ones, but they were larger (P ≤ 0.03). Invasion of exotic species was unrelated to native species richness when glade size was statistically controlled (P  =  0.88). Absence of a relationship is probably due to a lack of substantial competitive interactions. Most endemics occurred over a broad range of glade sizes emphasizing the point that glades of all sizes are worthy of protection.

The Huancabamba Biogeographical Province covers sections of southern Ecuador and northern Peru, and is well known for both its biodiversity and high levels of endemism. Páramo, a form of tropical alpine vegetation, covers less area in this region than in other tropical montane regions, and is dominated by shrubs instead of tussock grasses. A botanical inventory was conducted at a páramo site in Podocarpus National Park, southern Ecuador. Located between 3385 and 3250 m elevation, this site covers 2.4 ha of grass- and shrub-dominated vegetation communities. Fifty-five families, 90 genera and 136 species occurred, 27 of which are endemic to Ecuador. Both the combination of species and the growth forms differ markedly from those of most other páramo ecosystems. After describing the floristic characteristics of the site, I discuss the species composition, growth forms, and patterns of endemism in relation to various geographical and ecological factors.

Three hundred and forty eight vascular plant taxa were documented for Aztec Ruins National Monument, San Juan County, New Mexico. These include 13 new records for San Juan County, New Mexico. New records for Aztec Ruins National Monument include Sclerocactus cloveriae K. Heil subspecies cloveriae. This work was part of a biological inventory throughout the National Park Service as part of the Natural Resource Challenge, a legislative and administrative mandate.

A step-by-step procedure is described and demonstrated using the liana flora of Pennsylvania, USA, for the creation of simple biodiversity informatics applications in the form of Web-mashups. The target audience is non-tech-savvy biologists. For each liana species, the Web-based Liana Atlas of Pennsylvania creates Species Pages by aggregating information or direct links to information on taxonomy, distribution, morphology, genetics, as well as photographs and general encyclopedic or bibliographic information, “live” from third-party websites including the Global Biodiversity Information Facility, the USDA PLANTS database, Wikipedia®, and GenBank®. The result is an original, information-rich, fully illustrated application providing more up-to-date information on Pennsylvanian lianas in one place than had previously been available elsewhere. More importantly, the procedure described and files available at the demonstration website are portable and customizable to many other biogeographic regions or taxa, and its application requires only basic knowledge of Web navigation and text editors. We hope that this procedure will encourage others, including biologists with limited IT knowledge or at smaller institutions with limited resources, to contribute their own informatics applications valuable to local or regional interest-groups such as educators, students, and amateurs.

Solidago erecta has long been considered a member of the flora of New York, but recent studies have revealed that the six known voucher collections of S. erecta from New York had been misidentified and have been reassigned to S. speciosa or S. puberula. The earliest published reports of S. erecta from New York were partially based on the misapplication of scientific names and a misunderstanding of the taxonomy of the S. speciosa/S. erecta complex. Solidago erecta should be excluded from the flora of New York because it has not been documented from the state with voucher specimens.