Ageratina Altissima Research Articles

Complete genome sequence of an umbravirus from white snakeroot (Ageratina altissima).

Complete genome sequencing of a virus from a white snakeroot plant (Ageratina altissima (L.) King & H. Rob.) collected in the Great Smoky Mountains National Park, USA, revealed a quadricistronic organization resembling that of umbraviruses. ORFs 1 and 2 are putatively translated via a -1 ribosomal frameshift mechanism as a single polypeptide with a role in viral replication, whereas the 3'-proximal and extensively overlapping ORFs 3 and 4 code for proteins involved in long distance trafficing andcell-to-cell movementwithin the host. Sequence comparisons and phylogenetic analysis strongly suggested that this virus is a previously undescribed member of the genus Umbravirus (family Tombusviridae), for which the name "white snakeroot virus A" (WSVA) is proposed. In addition, we identified and initiated characterization of its possible helper virus, a putative new member of the genus Luteovirus.

Rayless goldenrod (Isocoma pluriflora) poisoning in chicks (Gallus gallusdomesticus)

Rayless goldenrod (Isocoma spp.) and white snakeroot (Ageratina altissima) poison livestock, wildlife and humans. The suggested toxin for both plants is tremetone, a mixture of benzofuran ketones. However, plant tremetone concentrations often do not correlate with poisoning, and they have not been identified in contaminated milk that poisons nursing neonates. This suggests there may be unidentified metabolites or toxins. Previous studies using various cell culture and large animal models have been inconsistent with varying animal response that often require large doses. The objective of this work is to document the toxicity of rayless goldenrod in California white leghorn chicks, a susceptible small animal model, that would require relatively small amounts of plant material or purified toxins. Four groups of 15 chicks were gavaged with finely ground I. pluriflora at rates of 0, 1%, 2% or 3% of their bodyweight per day for 7 days. After 7 exposure days the chicks were euthanized, necropsied and tissues were collected, fixed and examined microscopically. Myocyte damage was evaluated using clinical signs, weight gain, serum biochemical changes, and histologic lesions and scores. The 3% group had focally extensive myocyte degeneration and necrosis most severely affecting leg muscles (semitendinosus, iliotibialis, peroneus longus and gastrocnemius). This was supported by serum biochemical changes and reduced weight gains. These findings indicate young chicks are a sensitive model of toxicity that may be useful to better identify the rayless goldenrod and white snakeroot toxins, including those unidentified toxins of transmammary poisoning.

Competitive Interactions between Two Non-Native Species (Alliaria petiolata [M. Bieb.] Cavara & Grande and Hesperis matronalis L.) and a Native Species (Ageratina altissima [L.] R.M. King & H. Rob.).

Alliaria petiolata and Hesperis matronalis are wide-ranging non-native species in North America. Ageratina altissima is native to North America but has become a concern as an invasive species in Asia. A replacement series experiment was established to quantify the competitive interactions between these three species and to rank their relative competitiveness with each other. We assessed leaf count, chlorophyll content, and aboveground biomass with comparisons between replacement series mixtures and competition species. Overall leaf count and aboveground biomass were greatest in A. altissima and chlorophyll content was lowest in A. petiolata. Chlorophyll content and aboveground biomass were lower for A. altissima in competition with A. petiolata compared to H. matronalis. Leaf count for A. petiolata was lower in competition with A. altissima compared to H. matronalis. Aboveground biomass for H. matronalis was lower in competition regardless of the species compared to monoculture. There were also negative trends in biomass for A. petiolata in competition with increasing neighbors. However, for A. altissima, the negative trend in biomass was with A. petiolata, H. matronalis did not negatively affect A. altissima biomass. Our rank order of competitiveness was A. altissima > A. petiolata >> H. matronalis.

충남 광덕산의 식물상

Mt. Gwangdeok is 699.3m high and located between 36°65′00″~ 36° 71′00″ N in latitude and 27°01′00″~127° 05′00″ E in longitude. And it covered on boundary of Gwangdeok-myeon within Cheonan-si and Songak-myeon within Asan-si in Chungcheongnam-do. The investigated vascular plants consist of total 520 taxa: 6 forma, 50 varieties, 3 subspecies, 461 species, 315 genera, 99 families, 41 orders, 5 classes and 3 subphyla. And there are not found of extinct endangered Species in this study. But there are 3 taxa of Korean endemic plants: those are <italic>Weigela florida</italic> (Bunge) A.DC., <italic>Clematis trichotoma</italic> Nakai, <italic>Chrysosplenium sphaerospermum</italic> Maxim. and there found 4 taxa of disturbing invader plants: those are <italic>Ambrosia artemisiifolia</italic> L., <italic>Ambrosia trifida</italic> L., <italic>Eupatorium rugosum</italic> Houtt., <italic>Aster pilosus</italic> Willd. Therefore it needs to eliminate these Invaders and to campaign for hikers this alien taxa elimination movement before fruiting.

Assessment of the Spatial Invasion Risk of Intentionally Introduced Alien Plant Species (IIAPS) under Environmental Change in South Korea.

Simple SummaryThe spatial distribution and invasion risk of 10 intentionally introduced alien plant species (IIAPS) in South Korea were predicted from a species distribution model via a maximum entropy modeling approach. According to the model predictions, future environmental changes are likely to enlarge the range of the spatial distribution of all studied IIAPS in South Korea except Medicago sativa. We classified the IIAPS into three categories based on their spatial distribution and potential to spread; this revealed that four species (Coreopsis lanceolate, Eragrostis curvula, Ageratina altissima, and Lolium perenne) have the highest potential for invasion. Moreover, we classified invasion risk into three categories, low, moderate, and high, and estimated the area in each category. We found that, under current conditions, much of the country is at low risk (47.96%) of invasion, but by 2050 >54% of the country’s total area will be at high risk of invasion by IIAPS. Serious invasion of IIAPS into cropland, pastures, and forests results in the loss of native biodiversity and damage to the national economy. Therefore, immediate action is required to control and manage IIAPS in South Korea.Predicting the regions at risk of invasion from IIAPS is an integral horizon-scanning activity that plays a crucial role in preventing, controlling, and eradicating invasive species. Here, we quantify the spatial distribution area and invasion risk of IIAPS using a species distribution model under different levels of environmental change in South Korea. From the model predictions, the current average spatial extent of the 10 IIAPS is 33,948 km2, and the individual spatial extents are estimated to change by −7% to 150% by 2050 and by −9% to 156% by 2070. The spatial invasion risk assessment shows that, currently, moderate-to-high invasion risk is limited to coastal areas and densely populated metropolitan cities (e.g., Seoul, Busan, and Gwangju), but that the area with this level of risk is expected to spread toward the central and northern regions of the country in the future, covering 86.21% of the total area of the country by 2070. These results demonstrate that the risk of invasion by IIAPS is estimated to enlarge across the whole country under future environmental changes. The modeling system provided in this study may contribute to the initial control and strategic management of IIAPS to maintain the dynamic ecosystems of South Korea.

Introduction and Spread of the Invasive Alien Species Ageratina altissima in a Disturbed Forest Ecosystem

Invasive alien species (IAS) not only displace nearby indigenous plants and lead to habitat simplification but also cause severe economic damage by invading arable lands. IAS invasion processes involve external forces such as species characteristics, IAS assemblage traits, environmental conditions, and inter-species interactions. In this study, we analyzed the invasion processes associated with the introduction and spread of Ageratina altissima, a representative invasive plant species in South Korea. We investigated 197 vegetation quadrats (2 × 20 m) in regions bordering 47 forests in southern Seoul and Gyeonggi-do, South Korea. A total of 23 environmental variables were considered, which encompassed vegetation, topography, land use, and landscape ecology indices. The model was divided into an edge and an interior model and analyzed using logistic regression and a decision tree (DT) model. The occurrence of Ageratina altissima was confirmed in 61 sites out of a total of 197. According to our analysis, Ageratina altissima easily invaded forest edges with low density. The likelihood of its occurrence increased with lower elevation and gentler slope. In contrast, the spread of Ageratina altissima in the forest interior, especially based on seed spread and permeability, was favored by a lower elevation and gentler slopes. The analysis of Ageratina altissima settlement processes in forest edges coupled with the DT model demonstrated that land characteristics, such as the proximity to urbanized areas and the number of shrub and tree species, play a pivotal role in IAS settlement. In the forest interior, Ageratina altissima did not occur in 68 of the 71 sites where the soil drainage was under 2.5%, and it was confirmed that the tree canopy area had a significant impact on forest spread. Based on these results, it can be assumed that Ageratina altissima has spread in South Korean forests in much the same way as other naturalized species. Therefore, vegetation management strategies for naturalized species should be developed in parallel with land use management policy in regions surrounding forest edges to successfully manage and control Ageratina altissima invasion.

Effects of Low Light on Development of Ageratina altissima and Rudbeckia laciniata (Asteraceae), Species of the Tallgrass Prairie

How plants respond to low quantities of light could help in understanding plant development and ecology in habitats with changing light levels. Most previous studies have investigated shading by other plants, where spectral quality of light is changed. In this study, by contrast, several aspects of growth and reproduction were measured in Ageratina altissima and Rudbeckia laciniata (both grassland forbs in Asteraceae) grown for six weeks in a greenhouse where light was reduced to 10%, 50%, and 100% of ambient levels without changing spectral quality. Ageratina altissima was more responsive to light than was R. laciniata. In response to low light quantity, A. altissima displayed traits that were related to shade avoidance, common in grassland species, such as decreased chlorophyll content and biomass, fewer branches, leaves, and ramets, and decreased reproductive output. However, A. altissima also displayed traits that were consistent with shade tolerance, common in forest species, such as reduced elongation of stems, higher chlorophyll a/b ratio, reduced root and shoot biomass, and fewer and thinner leaves. Rudbeckia laciniata was less responsive to light treatments, only showing effects in leaf thickness and the SPAD chlorophyll index. There was no effect of light on leaf area, petiole length, or several chlorophyll fluorescence parameters in either species. Responses to low light quantity might involve a combination of shade avoidance and shade tolerance strategies in responsive species, potentially helpful as lighting conditions vary.

Garlic mustard as a potential driver of change in soil microbial community metabolism under controlled conditions

Alliaria petiolata (garlic mustard) is a biennial plant that is invasive in woodland areas in the Midwestern and Northeastern United States. Garlic mustard has been shown in previous studies to inhibit fungal and microbial growth. It therefore seems plausible that garlic mustard may alter the metabolic function of the soil microbial community and may impact these communities early during its biennial life-cycle. To address whether either of these possibilities occur, garlic mustard and a common native woodland plant, Ageratina altissima (white snakeroot), were grown from seed in soil collected from Iowa woodland plots free of garlic mustard in a controlled environment. After three months of growth, the soil was analyzed with Biolog EcoPlates to determine if garlic mustard seedlings impacted the metabolic profile of the soil microbial community differently than white snakeroot. An ANOSIM determined that garlic mustard and white snakeroot treatments had different effects on metabolic profiles of the soil microbial communities (p = 0.001, R = 0.301), and that garlic mustard depressed the metabolic potential of the soil microbial community. Additionally, the extent to which garlic mustard inhibits native plant growth while also stimulating the growth of subsequent generations of garlic mustard was studied. The growth of white snakeroot and garlic mustard were compared when grown in soil collected from woodland garlic mustard infestations to plants grown in woodland soil lacking garlic mustard. Wilcoxon Signed-Rank tests indicate that white snakeroot growth was positively impacted by soil history, while garlic mustard was not (p = 0.05; p = 0.60, respectively). We conclude that garlic mustard has the potential to alter the function and possibly the composition of the soil microbial communities, while surprisingly increasing the growth of white snakeroot seedlings. Furthermore, it seems that garlic mustard can elicit effects during its first three months of growth, suggesting that this plant should be targeted for removal early during its biennial life-cycle. Future studies should examine these findings in the field.

Effects of light levels on germination of five Asteraceae species native to the tallgrass prairie

The ability of plants to detect variations of light conditions is an essential mechanism for seed survival and germination. In this experiment, germinability and mean germination time were measured in five species of Asteraceae that are native to the tallgrass prairie in Kansas. Seeds were exposed to four light levels in a greenhouse experiment: 100% of natural light, approximately 50% of light, 10% of light, and dark conditions. Ageratina altissima (White snakeroot), Rudbeckia laciniata (Cutleaf coneflower), and Solidago ulmifolia (Elmleaf goldenrod) were non-photoblastic, as light levels had little effect on germinabilities. Aster drummondii (Drummond's aster) and Eutrochium purpureum (Sweet Joe-Pye weed) were positively photoblastic, as increasing light increased germinabilities. However, there were significant differences among species that might correlate with ecological roles. Ageratina altissima and R. laciniata had fast germinating seeds ( 10 d) in all light levels. A. drummondii and E. purpureum had germination times that ranged from fast to intermediate to slow, depending on light levels. Mean germination times decreased with increased light. Measurements of germinability and mean germination time are essential for understanding establishment, succession, and regeneration processes that occur in prairie communities.

Identifying habitats and corridors of an invasive plant, Ageratina altissima, in an urban forest

The spread of invasive plants in urban forests is of great concern to land managers and ecologists. Here, we analyse the distribution pattern and potential occurrence of a problematic invasive plant, Ageratina altissima, on Mt. Umyeon, in the Seoul metropolitan area of South Korea, using multiple species distribution modelling with geographic information system layers and a time series of Landsat 8 satellite imagery data. Also, we identify this species’ potential dispersal corridors using a network-based landscape lattice approach. All five species distribution models performed well with a range of test area under the receiver operating characteristic curve values of 0.843–0.899 with an average of 0.876. Distance from trails had the greatest effect on its occurrence probability, and generally exerted a negative influence within ca. 20 m of trails, indicating that urban forest trails facilitate the spread of invasive plants. Of the remote sensing-based predictors used, 7 August 2016 tasselled cap brightness index was an important variable having a negative effect on the presence of A. altissima. Elevation generally had a positive effect on its presence, although it was less important than tasselled cap brightness index. We explicitly detected the distribution pattern of high invasion risk corridors, mostly located on or around trails, which follow the central ridgeline of the study area. The results and approaches employed here can be useful for understanding, monitoring, and predicting invasive plant distribution and spread for the management of urban natural resources and biodiversity conservation.

Untargeted metabolic profiling of dogs with a suspected toxic mitochondrial myopathy using liquid chromatography-mass spectrometry

‘Go Slow myopathy’ (GSM) is a suspected toxic myopathy in dogs that primarily occurs in the North Island of New Zealand, and affected dogs usually have a history of consuming meat, offal or bones from wild pigs (including previously frozen and/or cooked meat). Previous epidemiological and pathological studies on GSM have demonstrated that changes in mitochondrial structure and function are most likely caused by an environmental toxin that dogs are exposed to through the ingestion of wild pig. The disease has clinical, histological and biochemical similarities to poisoning in people and animals from the plant Ageratina altissima (white snakeroot). Aqueous and lipid extracts were prepared from liver samples of 24 clinically normal dogs and 15 dogs with GSM for untargeted liquid chromatography-mass spectrometry. Group-wise comparisons of mass spectral data revealed 38 features that were significantly different (FDR<0.05) between normal dogs and those with GSM in aqueous extracts, and 316 significantly different features in lipid extracts. No definitive cause of the myopathy was identified, but alkaloids derived from several plant species were among the possible identities of features that were more abundant in liver samples from affected dogs compared to normal dogs. Mass spectral data also revealed that dogs with GSM have reduced hepatic phospholipid and sphingolipid concentrations relative to normal dogs. In addition, affected dogs had changes in the abundance of kynurenic acid, various dicarboxylic acids and N-acetylated branch chain amino acids, suggestive of mitochondrial dysfunction.

Effect of grinding and long-term storage on the toxicity of white snakeroot (Ageratina altissima) in goats

White snakeroot (Ageratina altissima) contains the putative toxin tremetone and can produce a disease called “trembles” or “milk sickness”. However the toxicity of tremetone has not been demonstrated in vivo. It has been reported that the plant is less toxic after drying and grinding. The objectives of these studies were to determine: 1) the toxic effect of grinding white snakeroot 4 months prior to dosing and, 2) the toxic effect of storing white snakeroot at ambient temperature for 5 years. Dried white snakeroot, ground 1 day, 1 month, and 4 months prior to dosing, was orally gavaged to goats at 2% of their body weight for up to 28 days or until they were minimally poisoned (minimal muscular weakness and increased serum creatine kinase (CK) activities). All four goats dosed with white snakeroot that had been ground 4 months previously and stored at room temperature were poisoned, became exercise intolerant, and had increased serum CK activities (>5600 U/ L). White snakeroot stored for 5 years was toxic as 3 of 5 dosed goats developed clinical disease within only 6 days of dosing even though approximately 80% of the tremetone in the plant had disappeared during the 5-year storage period. The results from this study demonstrate that previous grinding and extended storage did not significantly alter white snakeroot toxicity. The results also indicate that tremetone concentration is not the singular indicator of toxicity and that other white snakeroot toxins or toxic tremetone degradation products remain in dried, stored white snakeroot.

Influence of light intensity on germination, vegetative development, and reproduction of three species of Asteraceae native to Kansas

Plants are strongly influenced by a continuously changing light environment and their ability to detect light provides them vital information for their survival. However, most of the studies on photobiology are about commercial species and little is known about species native to Kansas and its region. Therefore, our objective was to analyze responses of three Asteraceae species native to Kansas under different light intensities during germination, vegetative development, and flowering. Seeds of Ageratina altissima, Eupatorium purpureum, and Solidago ulmifolia were measured for germination daily in conditions of dark, approximately 10%, 50%, and 100% of natural light. Seeds were later planted in soil and exposed to the same light conditions, and height, number of leaves, and chlorophyll (SPAD) were measured. Preliminary results show that A. altissima was the fastest species for germination and its germinability was consistent across light treatments. Germination in S. ulmifolia was also consistent across light treatments. For E. purpureum, germinability was higher in the light treatments than in the dark. A. altissima plants growing in 50% and 100% of light were taller and had more leaves than plants growing under 10% of light. Conventional plant responses to low light include growing taller under shaded conditions, although these plants responded differently. Most habitats in the prairie are exposed to bright sunlight and these results indicate these Asteraceae species are adapted to live and grow under bright light.

Ecological application of biotic resistance to control the invasion of an invasive plant, Ageratina altissima.

Biotic resistance is the ability of species in a community to limit the invasion of other species. However, biotic resistance is not widely used to control invasive plants. Experimental, functional, and modeling approaches were combined to investigate the processes of invasion by Ageratina altissima (white snakeroot), a model invasive species in South Korea. We hypothesized that (1) functional group identity would be a good predictor of biotic resistance to A. altissima, whereas a species identity effect would be redundant within a functional group, and (2) mixtures of species would be more resistant to invasion than monocultures. We classified 37 species of native plants into three functional groups based on seven functional traits. The classification of functional groups was based primarily on differences in life longevity and woodiness. A competition experiment was conducted based on an additive competition design with A. altissima and monocultures or mixtures of resident plants. As an indicator of biotic resistance, we calculated a relative competition index (RCI avg) based on the average performance of A. altissima in a competition treatment compared with that of the control where only seeds of A. altissima were sown. To further explain the effect of diversity, we tested several diversity–interaction models. In monoculture treatments, RCI avg of resident plants was significantly different among functional groups but not within each functional group. Fast‐growing annuals (FG1) had the highest RCI avg, suggesting priority effects (niche pre‐emption). RCI avg of resident plants was significantly greater in a mixture than in a monoculture. According to the diversity–interaction models, species interaction patterns in mixtures were best described by interactions between functional groups, which implied niche partitioning. Functional group identity and diversity of resident plant communities were good indicators of biotic resistance to invasion by introduced A. altissima, with the underlying mechanisms likely niche pre‐emption and niche partitioning. This method has most potential in assisted restoration contexts, where there is a desire to reintroduce natives or boost their population size due to some previous level of degradation.

한북정맥에 분포하는 관속식물상 - 광덕산, 청계산, 죽엽산을 중심으로 -

This study was carried out to offer the basic data for establishing the management plan and constructing the ecological data by surveying and analysing the flora distributed in main survey sites(Mt. Gwangdeok, Mt. Cheonggye and Mt. Jukyeop), Hanbuk-Jeongmaek. The flora were summarized, numbering 659 taxa including 99 families, 341 genera, 575 species, 4 subspecies, 69 varieties and 11 forms. The rare plants were 16 taxa including Tylophora floribunda, Hanabusaya asiatica, Lilium cernuum, Belamcanda chinensis and so forth. The Korean endemic plants were 24 taxa including Salix koriyanagi, Aconitum pseudolaeve, Clematis trichotoma, Hosta minor and so forth. The specific plants by floristic region were 95 taxa including 32 taxa of grade I, 31 taxa of grade II, 25 taxa of grade III, 5 taxa of grade IV and 2 taxa of grade V. The naturalized plants were 38 taxa including Fallopia dumetorum, Silene armeria, Cosmos bipinnatus, Poa pratensis and so forth. The invasive alien plants were 4 taxa including Ambrosia artemisiifolia, Ambrosia trifida, Aster pilosus and Eupatorium rugosum.

Green engineering of titanium dioxide nanoparticles using Ageratina altissima (L.) King &amp; H.E. Robines. medicinal plant aqueous leaf extracts for enhanced photocatalytic activity

Green engineering of titanium dioxide nanoparticles using Ageratina altissima (L.) King &amp; H.E. Robines. medicinal plant aqueous leaf extracts for enhanced photocatalytic activity

Toxicity of Compounds Isolated from White Snakeroot (Ageratina altissima) to Adult and Larval Yellow Fever Mosquitoes (Aedes aegypti)

Botanicals have been the source for several classes of pesticides for mosquitoes. However, increasing resistance to these products and reduced numbers of choices necessitate the search for new active ingredients. Ageratina altissima (L.) King & H. Rob. or white snakeroot, is found throughout the eastern United States and contains known toxic compounds. We examine chromenes (benzopyrans) and benzofurans isolated fiom this plant for larvicidal and adulticidal activity against the dengue vector Aedes aegypti L. Initial activity identified several compounds that were effective against either larvae or adults. Interestingly, only two compounds were effective against both larva and adults. Dose curves were constructed from further testing of these active compounds to allow. comparative ranking of efficacy. We identified dehydrotremetone as the most effective larvicide (0.03 ± 0.001 ng/μL) and 6-acetyl-7-methoxy-2,2- dimethylchromene as the most effective adulticide (1.17 ± 0.31 μg/org) although other compounds were also active. This study provides additional useful data for evaluation of chromenes and benzofurans as possible mosquiticidal agents.

Plant Host and Geographic Location Drive Endophyte Community Composition in the Face of Perturbation.

All plants form symbioses with endophytic fungi, which affect host plant health and function. Most endophytic fungi are horizontally transmitted, and consequently, local environment and geographic location greatly influence endophyte community composition. Growing evidence also suggests that identity of the plant host (e.g., species, genotype) can be important in shaping endophyte communities. However, little is known about how disturbances to plants affect their fungal symbiont communities. The goal of this study was to test if disturbances, from both natural and anthropogenic sources, can alter endophyte communities independent of geographic location or plant host identity. Using the plant species white snakeroot (Ageratina altissima; Asteraceae), we conducted two experiments that tested the effect of perturbation on endophyte communities. First, we examined endophyte response to leaf mining insect activity, a natural perturbation, in three replicate populations. Second, for one population, we applied fungicide to plant leaves to test endophyte community response to an anthropogenic perturbation. Using culture-based methods and Sanger sequencing of fungal isolates, we then examined abundance, diversity, and community structure of endophytic fungi in leaves subjected to perturbations by leaf mining and fungicide application. Our results show that plant host individual and geographic location are the major determinants of endophyte community composition even in the face of perturbations. Unexpectedly, we found that leaf mining did not impact endophyte communities in white snakeroot, but fungicide treatment resulted in small but significant changes in endophyte community structure. Together, our results suggest that endophyte communities are highly resistant to biotic and anthropogenic disturbances.

Seed longevity and dormancy state in a disturbance-dependent forest herb, Ageratina altissima

AbstractDoes seed dormancy allow disturbance-oriented forest herbs such as Ageratina altissima to persist in heterogeneous natural communities? To document seed longevity and dormancy state, Ageratina seeds were buried in nylon mesh bags in second-growth forest stands in south-eastern Ohio, USA. Bags were recovered at 2-month intervals, and seeds were tested for viability and germinability in the lab. Live seed numbers declined rapidly, with seed banks exhausted in an estimated 33–37 months. Seeds showed a strong dormancy polymorphism, with 71–84% of live seeds germinable between March and July, the season of natural seedling emergence. At other dates, most seeds appeared to be in a state of induced dormancy, allowing little (0–21%) germination. The slope aspect of the burial site, an important factor controlling above-ground vegetation, had no effect on seed longevity or dormancy condition. Dormancy in Ageratina appears to be adapted to allow opportunistic germination in late spring–early summer, but to prevent germination in less benign periods. Seed longevity is shorter than the natural frequency of gaps in mesophytic forest. We conclude that a long-term dispersal/dormancy trade-off is probably an oversimplification of the spatial ecology of this species. The primary function of dormancy appears to be short-term tracking of seasonal variation.

Toxicity of white snakeroot (Ageratina altissima) and chemical extracts of white snakeroot in goats.

White snakeroot (Ageratina altissima) is a sporadically toxic plant that causes trembles in livestock and milk sickness in humans that drink tainted milk. The putative toxin in white snakeroot is tremetone and possibly other benzofuran ketones, even though it has not been demonstrated in vivo. Toxic white snakeroot was dosed to goats, and they developed clinical signs of poisoning, exercise intolerance, significant increases in serum enzyme activities, and histological changes. Tremetone and the other benzofuran ketones were extracted with hexane; the extracts and residues were analyzed for tremetone and dosed to goats at tremetone and benzofuran ketone concentrations similar to the original plant material. However, none of the dosed goats developed the disease. The results demonstrate for the first time that white snakeroot is a potent myotoxin in goats and that other compound(s), which may be lost or modified during the extraction process, could be involved in causing trembles and milk sickness.