bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACTStudies 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

ABSTRACTAccording 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

ABSTRACTThis 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

ABSTRACTLittle 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

ABSTRACTA 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

ABSTRACTThe 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

ABSTRACTComparisons 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

ABSTRACTMany 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

ABSTRACTMost 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

ABSTRACTData 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

ABSTRACTGeographical 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

ABSTRACTThis 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.