bluuebunny/crossref_metadata_2025 huggingface dataset:
Weed dynamics in the Mediterranean urban ecosystem: ecology, biodiversity and management
Authors: Benvenuti S
Published: September 2004

This paper presents a review of weed dynamics in the Mediterranean urban ecosystem, seen both in an ecological and biological perspective and also in relation to the interaction between human activity and the survival strategies of the various phytocoenoses. Although generalizations on urban weeds cannot easily be drawn on account of the wide range of microenvironments, anemochoric dissemination mechanisms (Asteraceae), resilience (grasses) and perennation are of particular importance. The reasons underlying the undesirability of weeds in the urban environment are investigated. Not only are weeds considered unsightly, but they may also give rise to ‘functional’ obstacles, damaging sidewalks or clogging storm drains. Furthermore, they may adversely affect human health by releasing allergenic pollen into the atmosphere. Management of urban weeds is based almost exclusively on mechanical control, as chemical measures may involve a toxicity risk for man. Paradoxically, certain weeds species may however have a positive effect if they are linked to fauna (butterflies, birds, etc.) considered to give a favourable impression in the cityscape. Finally, the possibility of favouring the biodiversity of the urban ecosystem by introducing some wildflowers typically associated with the degree of biodiversity of the surrounding environment is discussed.
Spatial distribution of Lolium rigidum seedlings following seed dispersal by combine harvesters
Authors: Blanco‐Moreno J M , Chamorro L , Masalles R M , Recasens J , Sans F X
Published: September 2004

This paper considers the relationships between the dispersal of seeds and the distribution pattern of an annual weed. A comparative study of seed dispersal by combine harvesters, with and without a straw chopper attached, was established using Lolium rigidum, a common weed in Mediterranean cereal crops. Seed dispersal distance was quantified and the relationships between dispersal and fine‐scale seedling distribution evaluated. Primary dispersal of L. rigidum seeds occurs in a very limited space around the parent plants, but the density of seed is low because most seeds do not fall from spikes spontaneously. In contrast, many seeds are spread by combine harvesters. In this study the maximum dispersal exceeded 18 m from established stands in cereal fields, although the modal distance was close to the origin. In addition, the action of the combine harvesters tended to accumulate L. rigidum seeds predominantly under the straw swath, with some lateral movement. This action could explain the fine‐scale banded pattern of L. rigidum in cereal fields. Although the treatment of straw by the standard and straw chopper combines differed, the resultant seed distribution showed few differences.
Epidemiology of childhood psoriasis: a study of 419 patients from northern India
Authors: Kumar Bhushan , Jain Rajesh , Sandhu Kamaldeep , Kaur Inderjeet , Handa Sanjeev
Published: September 2004

Background  We undertook this study in order to determine the pattern and prevalence of childhood psoriasis in northern India and to highlight the differences and similarities with previous studies.

Materials and methods  In this retrospective epidemiologic study, the data from 419 children (less than 14 years of age) with psoriasis registered at the Psoriasis Clinic between January 1990 and December 2002 were included.

Results  The 419 children registered at the Psoriasis Clinic constituted 0.3% of the dermatology outpatients and 12.5% of the total psoriasis patients seen over a period of 13 years in the department. There were 219 (52.2%) boys and 200 (47.7%) girls, with a male to female ratio of 1.09 : 1. The age of onset ranged from 4 days to 14 years. The mean age of onset was 8.1 ± 2.1 years in boys and 9.3 ± 2.3 years in girls. The peak age of onset in boys was in the 6–10‐year age group, whereas the majority of girls showed an onset of psoriasis between the ages of 10 and 14 years. A positive family history was present in only 19 (4.5%) patients. The extensors of the legs were the most common initial site affected [105 (25%) cases], followed by the scalp [87 (20.7%)]. Classical plaque psoriasis was the most frequent clinical presentation [254 (60.6%) patients], followed by plantar psoriasis [54 (12.8%)]. Nail involvement was observed in 130 (31%) cases. All types of nail changes described in psoriasis were seen in these patients. Pitting was the most common nail change, followed by ridging and discoloration. Five children (1.1%) (three girls and two boys) had psoriatic arthropathy. Precipitating factors that brought about the onset of the disease or were associated with exacerbation could be recalled in only 28 (6.6%) patients. Koebnerization was observed in 27.9% of patients. Pruritus was the most frequent symptom, reported by 365 (87.1%) children. Twenty‐seven (6.4%) children had other concurrent mucocutaneous diseases (vitiligo, pityriasis alba, alopecia areata, ichthyosis vulgaris, halo nevus, aphthous stomatitis, urticaria, pityriasis versicolor, nummular eczema, salmon patch, and verrucous epidermal nevus). Eighteen children had systemic disorders, including seizures, bronchial asthma, mitral regurgitation, scleroderma, Down's syndrome, high arched palate, cholelithiasis, anterior mongoloid slant, and prognathism; however, these conditions were possibly chance findings only and no correlation with the age of onset or severity of the disease was found.

Conclusions  Our findings differ from those of previous studies in showing a delayed onset, equal sex distribution, less frequent facial involvement, uncommon guttate lesions, more frequent involvement of the soles, and a less frequent history of familial occurrence.
Invasion ofAgavespecies (Agavaceae) in south‐east Spain: invader demographic parameters and impacts on native species
Authors: Badano Ernesto I. , Pugnaire Francisco I.
Published: September 2004

Several mechanisms have been proposed to explain the success of invasive species in new environments. A species may become invasive when a new site provides the potential for positive rates of population growth. This may be the case of severalAgavespecies introduced to Spain in the 1940s. In this paper we document factors that promote large increases of populations of these species, and their effects on native plant communities in two sites of SE Spain. Results showed higher rhizome and bulbil production, and higher establishment rates by agaves in sandy soils than in clay soils. In their native habitats, agaves have low establishment rates and sandy soils are rare. This suggests that sandy soils are an opportunity which releases the clonal reproduction ofAgave. The effects of agaves on the physiological performance and reproduction of native species were negative, positive or neutral, depending on the size and rooting depth of neighbours. Assemblages of native species growing withinAgavestands had lower diversity than non‐invaded sites. Our data show thatAgavestands have positive growth rates in SE Spain, and suggest that sandy soils are a niche dimension enhancing the invasion in these new habitats.
Predicting rapid invasion of the Florida Everglades by Old World Climbing Fern (Lygodium microphyllum)
Authors: Volin John C. , Lott Michael S. , Muss Jordan D. , Owen Dianne
Published: September 2004

Lygodium microphyllum (Cav.) R. Br. (Lygodiaceae) is a climbing fern that is becoming one of the worst non‐indigenous invasive plant species in the greater Everglades ecosystem of southern Florida, USA. We examined the fern across a range of scales including the seasonality of its spore production, its height growth within infested sites and its community ecology. These attributes, combined with a series of aerial transects that identified L. microphyllum infestations across southern Florida, were used to develop a spatial model to predict its future spread in the Everglades landscape. The model shows that this non‐indigenous invader could become widely established throughout the Everglades by 2014. Although several factors, such as release from natural enemies, may help explain the invasion success of L. microphyllum, it appears likely that traits related to its reproduction, such as propagule pressure, and its ability to grow in a low‐light understorey environment, may be among the most important in explaining its ability to invade both disturbed and undisturbed areas far from source populations.
Predicting patterns of non‐native plant invasions in Yosemite National Park, California, USA
Authors: Underwood Emma C. , Klinger Rob , Moore Peggy E.
Published: September 2004

One of the major issues confronting management of parks and reserves is the invasion of non‐native plant species. Yosemite National Park is one of the largest and best‐known parks in the United States, harbouring significant cultural and ecological resources. Effective management of non‐natives would be greatly assisted by information on their potential distribution that can be generated by predictive modelling techniques. Our goal was to identify key environmental factors that were correlated with the percent cover of non‐native species and then develop a predictive model using the Genetic Algorithm for Rule‐set Production technique. We performed a series of analyses using community‐level data on species composition in 236 plots located throughout the park. A total of 41 non‐native species were recorded which occurred in 23.7% of the plots. Plots with non‐natives occurred most frequently at low‐ to mid‐elevations, in flat areas with other herbaceous species. Based on the community‐level results, we selected elevation, slope, and vegetation structure as inputs into the GARP model to predict the environmental niche of non‐native species. Verification of results was performed using plot data reserved from the model, which calculated the correct prediction of non‐native species occurrence as 76%. The majority of the western, lower‐elevation portion of the park was predicted to have relatively low levels of non‐native species occurrence, with highest concentrations predicted at the west and south entrances and in the Yosemite Valley. Distribution maps of predicted occurrences will be used by management to: efficiently target monitoring of non‐native species, prioritize control efforts according to the likelihood of non‐native occurrences, and inform decisions relating to the management of non‐native species in postfire environments. Our approach provides a valuable tool for assisting decision makers to better manage non‐native species, which can be readily adapted to target non‐native species in other locations.
Beautés fatales: Acanthaceae species as invasive alien plants on tropical Indo‐Pacific Islands
Authors: Meyer Jean‐Yves , Lavergne Christophe
Published: September 2004

Most, if not all, alien plant species of the family Acanthaceae (acanths) found in tropical islands were intentionally introduced as garden ornamentals, because of their showy coloured flowers, bracts or leaves. Some have ‘escaped’ gardens and have naturalized in human‐disturbed areas as weeds, adventives, or ruderal species. A few species have successfully invaded secondary and relatively undisturbed native wet forests. This paper reviews the naturalized alien acanths in tropical islands, and focuses on the currently invasive and potentially invasive species. This study is based on recent (1994–2004) botanical surveys and field observations conducted in several tropical oceanic islands of the Pacific and Indian Oceans, and on bibliographical searches of other tropical islands and countries. A total of 52 acanth species are naturalized in the Indo‐Pacific islands; 26 of them are native to Asia, 18 to tropical America, and only 8 to Africa. The number of naturalized acanths in selected tropical oceanic and continental islands varied from 7 to 25 species and the rate of naturalized acanths (number of naturalized species/number of introduced species) from 27% to 62%. We recorded eight major invasive species: the erect herbs or shrubs Justicia carnea, Odontonema strictum, Phlogacanthus turgidus, Sanchezia speciosa and Strobilanthes hamiltonianus form dense monospecific thickets in the understorey of wet forests; the woody vine Thunbergia grandiflora smothers native trees; the creeping herb Hemigraphis alternata forms dense carpets that totally cover the ground; and the herb Ruellia brevifolia colonizes the understorey of closed‐canopy wet forest. We also discuss eight potentially or incipient invasive acanths which are subspontaneous or sparingly naturalized, but which are not yet considered invasive. Most of the currently invasive acanths are sterile, the lack of fruit production being explained by the absence of pollinators and/or to their particular floral structure and reproduction modes. They reproduce vegetatively by stem fragmentation or by root suckers, and their range expansion is thus relatively slow. Their success may be attributed to their long (50–100 years) residence times, and long‐distance dispersal by humans. Many potentially invasive acanths are newly introduced ornamentals that produce seeds, thus constituting potentially greater threats. The Acanthaceae is not yet recognized as an ‘aggressive’ plant family (e.g. compared to the Fabaceae, Melastomataceae, Poaceae, or Rosaceae). It is, however, one of the most popular ornamental families in the Tropics, and should receive more attention because of the increasing number of current and incipient invasive species found in tropical islands.
Conifers as invasive aliens: a global survey and predictive framework
Authors: Richardson David M. , Rejmánek Marcel
Published: September 2004

We summarize information on naturalized and invasive conifers (class Pinopsida) worldwide (data from 40 countries, some with remote states/territories), and contrast these findings with patterns for other gymnosperms (classes Cycadopsida, Gnetopsida and Ginkgoopsida) and for woody angiosperms. Eighty conifer taxa (79 species and one hybrid; 13% of species) are known to be naturalized, and 36 species (6%) are ‘invasive’. This categorization is based on objective and conservative criteria relating to consistency of reproduction, distance of spread from founders, and degree of reliance on propagules from the founder population for persistence in areas well outside the natural range of species. Twenty‐eight of the known invasive conifers belong to one family (Pinaceae) and 21 of these are in one genus (Pinus). The Cupressaceae (including Taxodiaceae) has six known invasive species (4%) in four genera, but the other four conifer families have none. There are also no known invasive species in classes Cycadopsida, Gnetopsida or Ginkgoopsida. No angiosperm family comprising predominantly trees and shrubs has proportionally as many invasive species as the Pinaceae.

Besides the marked taxonomic bias in favour of Pinaceae, and Pinus in particular, invasiveness in conifers is associated with a syndrome of life‐history traits: small seed mass (< 50 mg), short juvenile period (< 10 year), and short intervals between large seed crops. Cryptomeria japonica, Larix decidua, Picea sitchensis, Pinus contorta, Pinus strobus, and Pseudotsuga menziesii exemplify this syndrome. Many rare and endangered conifer species exhibit opposite characters. These results are consistent with earlier predictions made using a discriminant function derived from attributes of invasive and noninvasive Pinus species. Informative exceptions are species with small seeds (< 4 mg, e.g. Chamaecyparis spp., Pinus banksiana, Tsuga spp. — mostly limited to wet/mineral substrates) or otherwise ‘non‐invasive’ characters (e.g. large seeds, fleshy fruits, e.g. Araucaria araucana, Pinus pinea, Taxus baccata that are dependent on vertebrates for seed dispersal). Most conifers do not require coevolved mutualists for pollination and seed dispersal. Also, many species can persist in small populations but have the genetic and reproductive capacity to colonize and increase population size rapidly. The underlying mechanisms mediating conifer invasions are thus easier to discern than is the case for most angiosperms. Further information is needed to determine the extent to which propagule pressure (widespread dissemination, abundant plantings, long history of cultivation) can compensate for low ‘inherent invasiveness’.
The rich generally get richer, but there are exceptions: Correlations between species richness of native plant species and alien weeds in Mexico
Authors: Espinosa‐García Francisco J. , Villaseñor José Luis , Vibrans Heike
Published: September 2004

Studies on the resistance of communities to plant invasions at different spatial scales have yielded contradictory results that have been attributed to scale‐dependent factors. Some of these studies argue either for or against Elton's notion of biotic resistance against invasions through diversity. We studied the correlation between alien weeds and native species, dividing the latter group into weedy and non‐weedy species, integrating various factors that influence diversity into an analysis on the scale of the federal states of Mexico. The resulting multiple‐regression models for native and alien weed species are robust (adjusted R2 = 0.87 and R2 = 0.69, respectively) and show a strong partial correlation of the number of weed species (native and alien) with the number of non‐weed native species. These results agree with studies showing a positive correlation between the number of native and alien species on larger scales. Both models also include human population density as an important predictor variable, but this is more important for alien weeds (β = 0.62) than for native weeds (β = 0.32). In the regression model for native weed species richness, the non‐cultivated (fallow) area (β = 0.24) correlated positively with native weed richness. In the model for alien weed species richness, the native weed species richness was an important variable (β = −0.51), showing a negative partial correlation (rpart = −0.4). This result is consistent with Elton's biotic resistance hypothesis, suggesting that biotic resistance is scale independent but that this may be masked by other factors that influence the diversity of both weeds and non‐weeds.
Breeding systems of invasive alien plants in South Africa: does Baker's rule apply?
Authors: Rambuda Tendani D. , Johnson Steven D.
Published: September 2004

According to Baker's Rule, plant species capable of uniparental reproduction are more likely to be successful colonists than are self‐incompatible or dioecious species. Controlled pollination experiments carried out on 17 invasive alien plant species in South Africa revealed that 100% were either self‐compatible or apomictic, and that 72% of these were capable of autonomous self pollination. The distribution of breeding systems among these invasive aliens is thus strongly skewed towards uniparental reproduction. While all 13 woody species in our survey showed a capacity for uniparental reproduction, this mode of reproduction is very rare among woody plants in general. Thus Baker's rule, which has generally been considered for short‐lived herbaceous plants, may also apply to invasive shrubs and trees. The study species exhibited high levels of fruit set (median = 71.5%). Supplemental hand‐pollination experiments carried out on five of the species showed that pollen availability did not limit fruit set. Further work is needed to establish the exact role of uniparental reproduction in various stages of the invasion process. In particular, we need to know whether uniparental reproduction provides reproductive assurance at the population establishment stage (as originally envisaged by Baker) or whether it plays a further role in alleviating pollen limitation in small and established populations.
Willow (Salix × rubens) invasion of the riparian zone in south‐eastern Australia: reduced abundance and altered composition of terrestrial arthropods
Authors: Greenwood Heather , O'Dowd Dennis J. , Lake P. S.
Published: September 2004

This study investigated the impact of invasion by an alien hybrid willow (the white‐crack willow, Salix × rubens) on the abundance and diversity of terrestrial arthropods along the lower Tarago River in south‐eastern Australia in spring and summer. Canopy arthropods were sampled by branch clippings, flying insects by sticky traps, and arthropod stream inputs by floating pan traps in willow‐invaded and uninvaded river sections. Willow‐invaded river sections had a significantly lower abundance and diversity of canopy arthropods, but the abundance and diversity of flying insects did not differ between willow‐invaded and native sections. Overall input of terrestrial arthropods was lower in willow‐invaded sections but this depended on sampling date. In general, differences in arthropod abundance between willow‐invaded and native river sections were greater in spring than summer, which may reflect seasonal changes in resource availability in native river sections. Morphospecies composition also differed significantly between willow‐invaded and native sections. These changes in abundance, diversity, and composition of terrestrial arthropods following plant invasion of the riparian zone may indirectly alter in‐stream food webs and have important effects on higher‐order consumers in the riparian zone.
A comparison of invasive and non‐invasive dayflowers (Commelinaceae) across experimental nutrient and water gradients
Authors: Burns Jean H.
Published: September 2004

Little is known about the traits and mechanisms that determine whether or not a species will be invasive. Invasive species are those that establish and spread after being introduced to a novel habitat. A number of previous studies have attempted to correlate specific plant traits with invasiveness. However, many such studies may be flawed because they fail to account for shared evolutionary history or fail to measure performance directly. It is also clear that performance is context dependent. Thus, an approach that corrects for relatedness and incorporates multiple experimental conditions will provide additional information on performance traits of invasive species.

I use this approach with two or three pairs of invasive and closely related non‐invasive species of Commelinaceae grown over experimental gradients of nutrient and water availability. Invasive species have been introduced, established, and spread outside their native range; non‐invasive species have been introduced, possibly (but not necessarily) established, but are not known to have spread outside their native range. The invasive species had higher relative growth rates (RGR) than non‐invasive congeners at high nutrient availabilities, but did not differ from non‐invasive species at low nutrient availabilities. This is consistent with a strategy where these particular invasive species are able to rapidly use available resources. Relative growth rates were also higher for two out of three invasive species across a water availability gradient, but RGR did not differ in plasticity between the invasive and non‐invasive species. This suggests that nutrient addition, but not changes in water availability, might favour invasion of dayflowers.

This approach is novel in comparing multiple pairs of invasive and non‐invasive congeners across multiple experimental conditions and allows evaluation of the robustness of performance differences. It also controls for some of the effects of relatedness that might confound multispecies comparisons.
A fuzzy classification technique for predicting species’ distributions: applications using invasive alien plants and indigenous insects
Authors: Robertson Mark P. , Villet Martin H. , Palmer Anthony R.
Published: September 2004

A new predictive modelling technique called the fuzzy envelope model (FEM) is introduced. The technique can be used to predict potential distributions of organisms using presence‐only locality records and a set of environmental predictor variables. FEM uses fuzzy logic to classify a set of predictor variable maps based on the values associated with presence records and combines the results to produce a potential distribution map for a target species. This technique represents several refinements of the envelope approach used in the BIOCLIM modelling package. These refinements are related to the way in which FEMs deal with uncertainty, the way in which this uncertainty is represented in the resultant potential distribution maps, and the way that these maps can be interpreted and applied. To illustrate its potential use in biogeographical studies, FEM was applied to predicting the potential distribution of three invasive alien plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.), and three native cicada species (Capicada decora Germar, Platypleura deusta Thun. and P. capensis L.) in South Africa, Lesotho and Swaziland. These models were quantitatively compared with models produced by means of the algorithm used in the BIOCLIM modelling package, which is referred to as a crisp envelope model (the CEM design). The average performance of models of the FEM design was consistently higher than those of the CEM design. There were significant differences in model performance among species but there was no significant interaction between model design and species. The average maximum kappa value ranged from 0.70 to 0.90 for FEM design and from 0.57 to 0.89 for the CEM design, which can be described as ‘good’ to ‘excellent’ using published ranges of agreement for the kappa statistic. This technique can be used to predict species’ potential distributions that could be used for identifying regions at risk from invasion by alien species. These predictions could also be used in conservation planning in the case of native species.
Why do alien plant species that reproduce in natural habitats occur more frequently?
Authors: Kühn Ingolf , Brandenburg Marlene , Klotz Stefan
Published: September 2004

The invasion process can be divided into several phases. We consider invasion patterns related to two aspects of the invasion process: the spread of a species in Germany as counted by the number of occupied grid cells, and the degree of naturalization in Germany (i.e. whether a plant species is exclusively naturalized in human‐made habitats or also in (semi‐)natural habitats). Although in Germany the area of natural habitats is smaller than that of human‐made habitats, the area of occupancy of the respective alien plant species is the opposite. We tested whether both patterns could be explained by niche‐breadth variables, namely the number of inhabited habitat types, and vegetation formations, the range of human impact levels, the number of inhabited continents, the number of inhabited floristic zones (climatic zones), and the amplitude of oceanity. Tests were conducted across species and across phylogenetically‐independent contrasts, using generalized linear models, in particular, hierarchical partitioning. The number of occupied grid cells could be explained by niche‐breadth variables, especially by number of habitats, number of formations, and amplitude of oceanity. Contrary to our expectations, none of these variables could explain the degree of naturalization in cross‐species analyses, and amplitude of oceanity is the only stably significant variable that explains the degree of naturalization when analysing phylogenetically‐independent contrasts. We conclude that the degree of naturalization is probably independent from niche breadth, and that properties of a larger area of occupancy, i.e. sample size (or propagule pressure), could be responsible for this pattern.
Comparing alien plant invasions among regions with similar climates: where to from here?
Authors: Pauchard Aníbal , Cavieres Lohengrin A. , Bustamante Ramiro O.
Published: September 2004

Comparisons between regions with similar climates have traditionally helped to tackle big questions in evolutionary ecology and historical biogeography. We claim that plant invasion ecology can benefit greatly from further and better comparisons at regional and global scales. In this note we discuss the potentials and limitations of comparing climatically analogous regions to provide novel insights into the mechanisms of alien plant invasions. Comparisons among areas with similar climates have the advantage that some features of the abiotic environment are within a narrower range of variation, enabling the researcher to focus on the effects of propagule pressure, microenvironmental differences and, more importantly, the biotic environment in the invasion process. However, there are two major issues that limit the strengths of such comparisons: (1) non‐standardized databases of alien species, especially in less developed countries; and (2) deficient sampling designs. We argue that we should take advantage of comparative studies of alien plant invasions across regions with similar climates not only to obtain useful insights about invasions, but to search for generalities beyond invasion ecology that contribute to our knowledge of natural systems.
Reconstructing 50 years of Opuntia stricta invasion in the Kruger National Park, South Africa: environmental determinants and propagule pressure
Authors: Foxcroft Llewellyn C. , Rouget Mathieu , Richardson David M. , Mac Fadyen Sandra
Published: September 2004

Many factors influence the spread dynamics and distribution of invasive alien organisms. Despite progress in unravelling the determinants of invasiveness and invasibility, robust, spatially‐explicit predictive models for explaining real‐world invasion dynamics remain illusive. Reconstructing invasion episodes is a useful way of determining the roles of different factors in mediating spread and proliferation. In many cases, however, human‐aided dispersal and other anthropogenic factors blur the roles of natural controlling factors.

We describe the reconstruction of an isolated invasion event from a known source: the 50‐year invasion history of Opuntia stricta in the Kruger National Park. Our aim was to explore the relative roles of environment and propagule supply in shaping the invasion pattern.

Environmental variables (landscape heterogeneity and distance from water sources) were moderately useful for explaining the presence/absence of O. stricta in 1‐ha cells across the 660 km2 (53% of cells correctly classified). Adding fire frequency increased the accuracy of the model (68%). However, when we considered the role of propagule pressure (measured as the distance of sites from the known primary invasion focus and putative secondary invasion foci), model accuracy was greatly improved (77%). No environmental variables or propagule pressure correctly explained spatial variation in abundance (expressed as cladode density in 1‐ha cells). We discuss implications of the importance of propagule supply for modelling and managing invasions.
Mapping the potential ranges of major plant invaders in South Africa, Lesotho and Swaziland using climatic suitability
Authors: Rouget Mathieu , Richardson David M. , Nel Jeanne L. , Le Maitre David C. , Egoh Benis , Mgidi Theresa
Published: September 2004

Most national or regional initiatives aimed at managing biological invasions lack objective protocols for prioritizing invasive species and areas based on likely future dimensions of spread. South Africa has one of the most ambitious national programmes for managing plant invasions in the world. There is, however, no protocol for assessing the likely future spread patterns needed to inform medium‐ to long‐term planning. This paper presents an assessment of the climatic correlates of distribution of 71 important invasive alien plants, and an analysis of the implications of these findings for future invasions in different vegetation types in South Africa, Lesotho and Swaziland over the next few decades. We used a variant of climatic envelope models (CEMs) based on the Mahalanobis distance to derive climatic suitability surfaces for each species. CEMs were developed using the first three principal components derived from an analysis of seven climatic variables. Most species are currently confined to 10% or less of the region, but could potentially invade up to 40%. Depending on the species, between 2% and 79% of the region is climatically suitable for species to invade, and some areas were suitable for up to 45 plant invaders. Over one third of the modelled species have limited potential to substantially expand their distribution. About 20% of the vegetation types have low invasion potential where fewer than five species can invade, and about 10% have high invasion potential, being potentially suitable for more than 25 of the plant invaders. Our results suggest that management of the invasive plant species that are currently most widespread should focus on reducing densities, for example through biological control programmes, rather than controlling range expansions. We also identify areas of the region that may require additional management focus in the future.
Plant invasions in Taiwan: Insights from the flora of casual and naturalized alien species
Authors: Wu Shan‐Huah , Hsieh Chang‐Fu , Chaw Shu‐Miaw , Rejmánek Marcel
Published: September 2004

Data on floristic status, biological attributes, chronology and distribution of naturalized species have been shown to be a very powerful tool for discerning the patterns of plant invasions and species invasiveness. We analysed the newly compiled list of casual and naturalized plant species in Taiwan (probably the only complete data set of this kind in East Asia) and found that Taiwan is relatively lightly invaded with only 8% of the flora being casual or naturalized. Moreover, the index of casual and naturalized species per log area is also moderate, in striking contrast with many other island floras where contributions of naturalized species are much higher. Casual and naturalized species have accumulated steadily and almost linearly over the past decades. Fabaceae, Asteraceae, and Poaceae are the families with the most species. However, Amaranthaceae, Convolvulaceae, and Onagraceae have the largest ratios of casual and naturalized species to their global numbers. Ipomoea, Solanum and Crotalaria have the highest numbers of casual and naturalized species. About 60% of all genera with exotic species are new to Taiwan. Perennial herbs represent one third of the casual and naturalized flora, followed by annual herbs. About 60% of exotic species were probably introduced unintentionally onto the island; many species imported intentionally have ornamental, medicinal, or forage values. The field status of 50% of these species is unknown, but ornamentals represent noticeable proportions of naturalized species, while forage species represent a relatively larger proportion of casual species. Species introduced for medicinal purposes seem to be less invasive. Most of the casual and naturalized species of Taiwan originated from the Tropical Americas, followed by Asia and Europe.
Latitudinal trends in growth and phenology of the invasive alien plant Impatiens glandulifera (Balsaminaceae)
Authors: Kollmann Johannes , Bañuelos María José
Published: September 2004

Geographical differentiation of populations can be interpreted as a result of adaptive processes in response to environmental gradients and biotic interactions. Such adaptations are particularly interesting in invasive alien species which have been present in an area for a relatively short time. There are few observations of latitudinal trends in alien plants, and no account exists for Impatiens glandulifera, a problematic annual weed in most countries of central and north‐western Europe. Here we describe variation in growth and phenology in 26 populations of this species from nine European regions in a common garden in Denmark. Above‐ground biomass (an estimate of fecundity), height and basal diameter were lower in the northern populations which were first to produce flowers. Some differences were also observed in biomass allocation to leaves, flowers and fruits, albeit without a latitudinal pattern. The latitudinal trends in growth and survival disappeared in a field experiment, probably due to suboptimal site conditions. Most variation in plant traits was explained by differences among regions with some minor effects of populations within regions. Besides latitude, no other geographical, climatic or population trait correlated with the observed differences in growth and phenology. Differences in latitude may mainly represent variation in length of the growing season. The causes and potential consequences of such latitudinal trends for population dynamics and dispersal of alien plants are discussed.
Plant invasion ecology — dispatches from the front line
Authors: Richardson David M.
Published: September 2004

This issue of Diversity and Distributions carries papers on a wide range of topics dealing with invasions of introduced plant species. The collection of articles did not arise from a conference or workshop, but grew from a founder population of contributed manuscripts. Some additional papers were solicited to ensure coverage of other established or emerging fields of research in plant invasion ecology. The compilation represents a reasonable cross section of issues that currently occupy plant invasion ecologists. The editorial places the contributions in context and summarizes some key findings. It also suggests some profitable avenues for future research in plant invasion ecology.
An anaesthetic protocol in the young domestic pig allowing neuromuscular blockade for studies of cardiac function following cardioplegic arrest and cardiopulmonary bypass
Authors: Fanneløp T. , Dahle G. O. , Matre K. , Segadal L. , Grong K.
Published: September 2004

Background:  Neuromuscular blockade should, for ethical reasons, not be allowed in animal experiments unless the use is strongly motivated. Beforehand, the anaesthetic protocol must be documented without muscle relaxation in the species studied. Documentation is difficult to obtain from the scientific literature. When focusing on cardiac function over time, in particular, the ideal anaesthetic protocol should cause no or minor alterations in cardiac variables.

Methods:  We intended to document an anaesthetic protocol involving ventilation with N2O combined with loading doses and continuous infusions of pentobarbital, fentanyl and midazolam in seven pigs by applying potentially painful stimuli every 15 min for 7 h. Subsequently, left ventricular global and regional function was studied with conductance catheter and strain rate imaging by echocardiography in eight pigs with pancuronium included.

Results:  Pigs without pancuronium were completely immobilized and unresponsive to potentially painful stimuli and sternotomy, with no accumulation or degradation of anaesthetic agents. With pancuronium included, left ventricular preload gradually decreased together with reduction of cardiac index from 3.52 ± 0.14 at 2 h to 2.84 ± 0.11 L min−1 · m−2 (±SEM) after 7 h of observation. Preload recruitable stroke work decreased after 7 h, whereas peak systolic strain in the anterior left ventricular wall and load‐independent indices of diastolic function were not significantly altered.

Conclusion:  In specific experimental protocols, the anaesthetic protocol described could allow the use of muscular paralysis in young domestic pigs, for instance when involving hypothermic cardiopulmonary bypass, cardioplegic arrest and reperfusion.
Expiratory flow limitation in morbidly obese postoperative mechanically ventilated patients
Authors: Koutsoukou A. , Koulouris N. , Bekos B. , Sotiropoulou C. , Kosmas E. , Papadima K. , Roussos C.
Published: September 2004

Although obesity promotes tidal expiratory flow limitation (EFL), with concurrent dynamic hyperinflation (DH), intrinsic PEEP (PEEPi) and risk of low lung volume injury, the prevalence and magnitude of EFL, DH and PEEPi have not yet been studied in mechanically ventilated morbidly obese subjects.

In 15 postoperative mechanically ventilated morbidly obese subjects, we assessed the prevalence of EFL [using the negative expiratory pressure (NEP) technique], PEEPi, DH, respiratory mechanics, arterial oxygenation and PEEPi inequality index as well as the levels of PEEP required to abolish EFL.

In supine position at zero PEEP, 10 patients exhibited EFL with a significantly higher PEEPi and DH and a significantly lower PEEPi inequality index than found in the five non‐EFL (NEFL) subjects. Impaired gas exchange was found in all cases without significant differences between the EFL and NEFL subjects. Application of 7.5 ± 2.5 cm H2O of PEEP (range: 4–16) abolished EFL with a reduction of PEEPi and DH and an increase in FRC and the PEEPi inequality index but no significant effect on gas exchange.

The present study indicates that: (a) on zero PEEP, EFL is present in most postoperative mechanically ventilated morbidly obese subjects; (b) EFL (and concurrent risk of low lung volume injury) is abolished with appropriate levels of PEEP; and (c) impaired gas exchange is common in these patients, probably mainly due to atelectasis.
Different Human Interleukin‐4 Mutants Preferentially Activate Human or Murine Common Receptor γ Chain
Authors: Lischke Antje , Kammer Winfried , Friedrich Karlheinz
Published: September 2004

Interleukin‐4 (IL‐4) shows species‐specific activity due to species‐restricted interaction with the IL‐4 receptor α (IL‐4Rα) chain. The second subunit of a functional IL‐4 receptor, the common γ chain (γc), is more promiscuous, since human IL‐4 is able to activate IL‐4 receptor complexes containing either human or murine common γ receptor chain (γc). We have stably transfected factor‐dependent mouse cells of myeloid and lymphoid origin with combinations of human IL‐4Rα and γc. derivatives. In these cell lines, both human and murine γc receptors as well as IL‐4Rα chains from both species are simultaneously expressed. Both versions of γc readily form ternary complexes with either human IL‐4 and human IL‐4Rα or murine IL‐4 and murine IL‐4Rα. Due to distinct ligand‐binding properties of human and murine γc, the two receptor complexes can be activated preferentially by different mutant variants of human IL‐4. The contribution of murine common γ chain to human IL‐4‐induced signal transduction is suppressed by an inhibitory antibody directed to the extracellular domain of the mouse γc. We present evidence that the two IL‐4R complexes functionally interfere with each other and compete for response‐limiting signalling components.
Sequential 1H and 15N Nuclear Magnetic Resonance Assignments and Secondary Structure of the Lipoyl Domain of the 2‐Oxoglutarate Dehydrogenase Complex from Azotobacter Vinelandii
Authors: Berg Axel , Smits Otto , de Kok Arie , Vervoort Jacques
Published: September 2004

A 79‐amino‐acid polypeptide, corresponding to the lipoyl domain of the succinyltransferase component of the 2‐oxoglutarate dehydrogenase multienzyme complex from Azotobacter vinelandii, has been sub‐cloned and produced in Escherichia coli. Complete sequential 1H and 15N resonance assignments for the lipoyl domain have been obtained by using homo‐ and hetero‐nuclear NMR spectroscopy. Two anti‐parallel β‐sheets of four strands each were identified from characteristic NOE connectivities and 3JHNα values. The lipoyl‐lysine residue is found in a type‐I turn connecting two β‐strands. The secondary structure of the lipoyl domain very much resembles the secondary solution structure of the N‐terminal lipoyl domain of the A. vinelandii pyruvate dehydrogenase complex, despite the sequence identity of 25%. A detailed comparison of the NMR‐derived parameters of both lipoyl domains, i.e. chemical shifts, NH‐exchange rates, NOEs, and 3JHNα values suggests a high structural similarity in solution between the two lipoyl domains. Preliminary tertiary‐structure calculations confirm that these lipoyl domains have very similar overall folds. The observed specificity of the 2‐oxo acid dehydrogenase components of both complexes for these lipoyl domains is discussed in this respect.
Isolation of the Endothelin B Receptor from Bovine Lung Structure, Signal Sequence, and Binding Site
Authors: Hick Simone , Heidemann Ina , Soskic Vukic , MÜller‐Esterl Werner , Godovac‐Zimmermann Jasminka
Published: September 2004

Bovine lung endothelin‐B receptor has been isolated in good yield with a new procedure involving the use of endothelin‐1 coupled to iminobiotin with a long spacer and avidin‐agarose affinity chromatography. Contrary to previous reports, evidence has been obtained that the native form of this receptor corresponds to the full‐length transcript expected on the basis of cDNA clones. The binding of endothelin to a variety of shortened fragments of the full receptor suggests that the long N‐terminal sequence of this receptor has very little influence on the binding of endothelin and that the main determinants of the endothelin binding site might be constituted by residues in the sixth, and possibly the seventh, transmembrane helices.
Identification of Trp300 as an Important Residue for Escherichia Coli Leader Peptidase Activity
Authors: Kim Yong‐Tae , Muramatsu Tomonari , Takahashi Kenji
Published: September 2004

We previously reported that leader peptidase from Escherichia coli was extensively inactivated by reaction with N ‐bromosuccinimide with concomitant and selective modification of the Trp300 and Trp310 residues [Kim, Y.‐T., Muramatsu, T. & Takahashi, K. (1995) J. Biochem. (Tokyo) 117, 535–544]. This indicated that one or both of these tryptophan residues are important for the activity of the enzyme. In order to define further the role of individual tryptophan residues in the activity of leader peptidase, site‐directed mutagenesis studies were performed to replace each tryptophan residue with phenylalanine and/or alanine. The replacements of Trp20, Trp59, Trp261, Trp284, and Trp310 with phenylalanine hardly affected the enzyme activity toward a synthetic peptide substrate and the ability to complement the temperature sensitivity of the mutant leader peptidase in E. coli IT41. In contrast, the activity toward the synthetic substrate was significantly decreased by replacement of Trp300 with phenylalanine or alanine. The kcat, values of the W300F and W300A mutant enzymes were reduced to 42% and 22%, respectively, of that of the wild‐type enzyme, whereas the Km values of these mutant enzymes were almost identical with that of the wild‐type enzyme. Moreover, the complementing ability in E. coli IT41 was lost (almost) completely when Trp300 was replaced with phenylalanine or alanine. These results strongly indicate that Trp300 in leader peptidase is important for the catalytic mechanism and/or the construction of the active site structure of the enzyme.