Assessing the risk of potentially invasive plant species in central Europe

A risk assessment system was developed to assess the invasion potential of new environmental weeds in central Europe. A pre-evaluation step excludes species that are officially controlled, widespread, or intended for use in protected cultures only. Species eligible for risk assessment are classified into three categories (high risk, further observation required, low risk) by rating them according to various biogeographical and ecological aspects. The rating system was validated by testing 47 well-known invasive plant species of temperate Europe and 193 exotic plants which have failed to establish themselves in Switzerland. The overall accuracy was 65%. Accuracy of correctly predicting invasive species was 77%, while accuracy of correctly predicting non-invasive species was 62%. The proposed risk assessment protocol should be understood as a first attempt for a European country and needs modifications. These can only be achieved by applying the system in practice.     

Estimating the growth of a newly established moose population using reproductive value

Estimating the population growth rate and environmental stochasticity of long-lived species is difficult because annual variation in population size is influenced by temporal autocorrelations caused by fluctuations in the age-structure. Here we use the dynamics of the reproductive value to estimate the long-term growth rate s and the environmental variance of a moose population that recently colonized the island of Vega in northern Norway. We show that the population growth rate was high (ŝ=0.26). The major stochastic influences on the population dynamics were due to demographic stochasticity, whereas the environmental variance was not significantly different from 0. This supports the suggestion that population growth rates of polytocous ungulates are high, and that demographic stochasticity must be assessed when estimating the growth of small ungulate populations.     

Immunohistochemical characteristics of chicken spleen ellipsoids using newly established monoclonal antibodies

Ellipsoids, the extra-vasculature sites surrounding penicilliary capillaries of the chicken spleen, play critical roles in the immune response and also in the clearance of pathogens or other particles. The meshwork of ellipsoids is formed by fibroblastic reticular cells. To characterize ellipsoidal reticular cells, a series of monoclonal antibodies against the chicken spleen have been developed. Of these antibodies, CSA-1 antibody reacts with fibroblastic reticular cells in ellipsoids and with endothelial cells. The reticular nature of positive cells in ellipsoids is indicated by immuno-electron microscopy, and by double-staining with anti-heat-shock protein 47 kDa (hsp47) antibody. The reaction of CSA-1 with reticular cells is limited in ellipsoids; CSA-1 does not react with reticular cells in other lymphoid organs. These findings indicate that ellipsoidal reticular cells share the antigen with endothelial cells. Ontogenic studies reveal that, on embryonic day 18, the development of ellipsoids is completed, penicilliary capillaries become fenestrated, and CSA-1 expression in ellipsoids begins. These findings suggest that CSA-1 is expressed on the cell surface of ellipsoidal reticular cells once they are exposed to blood flow.     

Reticulate evolution in the natural range of the invasive wetland tree species Melaleuca quinquenervia

The Melaleuca leucadendra complex (broad-leaf paperbarks; Myrtaceae) is a dominant component of the tropical and sub-tropical biota of Australia, particularly in wetlands of high conservation significance. In Florida and other parts of the Americas, however, one member of the group (Melaleuca quinquenervia) is a serious ecological and economic weed. Understanding the relationships and evolution of the group is integral to both conservation and biocontrol efforts. Although the complex is currently considered to include up to 14 species, there has been some concern over taxonomic boundaries within the complex because most species are circumscribed only by combinations of characters, each of which also occurs in other species. Here, DNA sequence data derived from the chloroplast and two nuclear regions are used to explore the relationships of M. quinquenervia. We find little evidence for clear species boundaries within the M. leucadendra complex in general, with regional sharing of chloroplast haplotypes across morphologically defined taxa, indicating asymmetrical introgression or retention of ancestral haplotypes (lineage sorting). Phylogenies were further confounded by the recovery of multiple copies of both nuclear regions sequenced (ITS and rpb2) from many individuals. There was no clear evidence of polyploidy or pseudogenes, but multiple duplications of rpb2 could not be ruled out. Parsimony networks of the nuclear ITS region show some clustering of haplotypes by morphospecies but there is also evidence of both hybridisation and recombination. Signals of introgression were also evident in rpb2, supporting an hypothesis of recent or ongoing gene flow between M. quinquenervia and other members of the M. leucadendra complex. Both relaxed and fixed molecular-clock dating estimate the introgression to have occurred sometime within the past seven million years (95% CI: 0.7-18). The New Caledonian population of M. quinquenervia appears to have been established by dispersal from Australia during this period. M. quinquenervia is found to have alleles closely related to multiple different morphotaxa within the M. leucadendra complex, suggesting considerable past introgression into this taxon from some other members of the M. leucadendra complex, and this has implications for biocontrol efforts. The M. leucadendra complex appears to reflect early to intermediate stages of speciation, possibly driven by different ecologies.     

Inhibition between invasives: a newly introduced predator moderates the impacts of a previously established invasive predator

1. With continued globalization, species are being transported and introduced into novel habitats at an accelerating rate. Interactions between invasive species may provide important mechanisms that moderate their impacts on native species. 2. The European green crab Carcinus maenas is an aggressive predator that was introduced to the east coast of North America in the mid-1800 s and is capable of rapid consumption of bivalve prey. A newer invasive predator, the Asian shore crab Hemigrapsus sanguineus, was first discovered on the Atlantic coast in the 1980s, and now inhabits many of the same regions as C. maenas within the Gulf of Maine. Using a series of field and laboratory investigations, we examined the consequences of interactions between these predators. 3. Density patterns of these two species at different spatial scales are consistent with negative interactions. As a result of these interactions, C. maenas alters its diet to consume fewer mussels, its preferred prey, in the presence of H. sanguineus. Decreased mussel consumption in turn leads to lower growth rates for C. maenas, with potential detrimental effects on C. maenas populations. 4. Rather than an invasional meltdown, this study demonstrates that, within the Gulf of Maine, this new invasive predator can moderate the impacts of the older invasive predator.     

Assessing population increase as a possible outcome to management of invasive species

Some efforts to reduce invasive populations have paradoxically led to population increases. This phenomenon, referred to as overcompensation, occurs when reduced intraspecific pressures increase juvenile survival or maturation rates, leading to increased population size. Overcompensation in response to eradication efforts could derail management efforts, so it would be beneficial to evaluate the likelihood of overcompensation prior to removal. We conducted a series of experiments to examine the potential for overcompensation of a non-native population of the European green crab, Carcinus maenas, which was being removed in Bodega Harbor, California. First, we examined the impact of adults on juvenile survival by measuring adult cannibalism on juveniles in the presence and absence of alternative prey, and the survival of tethered juveniles at varying adult densities. Second, we examined how adult presence affected juvenile short-term foraging and growth rates. Although adult presence reduced juvenile short-term foraging, we detected only minimal cannibalism and found no evidence that adults greatly reduce juvenile growth or survivorship. These results suggest that overcompensation is not likely to occur in this population in response to removal. We assessed this prediction using pre- and post-removal surveys of juvenile recruitment in Bodega Harbor compared to nearby populations, testing for evidence of overcompensation. Relative juvenile abundance did not statistically increase in removal compared to reference populations, consistent with our conclusion from the experiments. This experimental approach which focuses on an organism’s population biology provides a tool to assess capacity for assessing the capacity for overcompensation in management strategies for invasive species.     

The infinitesimal, the deterministic, and the probabilistic: Alternate container inspection policies in invasive species management

Recently, Batabyal and Nijkamp (2005, Stochastic Environmental Research and Risk Assessment 19: 340–347) have shown that in an inspection cycle, regardless of whether the inspection policy choice is made on the basis of an optimization exercise or on the basis of a rule of thumb, the “container policy” dominates the “temporal policy” because the former results in lower long run expected net cost (LRENC) from inspections. In this paper, we continue this line of inquiry and analyze container policies in three scenarios. In the first scenario the time taken to conduct inspections is negligible. In the second scenario, this inspection time is deterministic and in the third scenario this inspection time is stochastic. Specifically, we compare and contrast the LRENC and the optimal container policy in each of these three scenarios.      

Modeling the spread of invasive species using dynamic network models

Spread dynamics of biological invasions are influenced by both the availability and spatial arrangement of suitable habitat. As such, invasive spread can be considered to occur across a network of nodes, representing patches of suitable habitat, with linkages representing the potential for movement between habitat patches. While static network models can provide valuable insight into the potential framework of nodes and linkages across which spread could occur, they offer little information on the actual spatiotemporal dynamics of range expansion processes. Here, we explore the development and application of dynamic network models (DNMs) to model the spread of invasive species. DNMs accommodate temporal dynamics in the utilization of nodes and the connections between them and can flexibly perform simulations at the spatial scales of observational data. As case studies, we develop DNMs to simulate the spread of a generalist forest pathogen and the hemlock woolly adelgid (Adelges tsugae Annand). We highlight the utility of DNMs for identifying habitat patches that contribute most to spread across the landscape and for visualizing emergent spread dynamics. While currently underutilized in ecology as compared to static network models, DNMs are potentially applicable to numerous research and management questions relevant to biological invasions and the more general phenomena of range expansion.     

Modeling future range expansion and management strategies for an invasive squirrel species

Successful management of an invasive species requires in depth knowledge of the invader, the invaded ecosystem, and their interactions. The complexity of the species-system interactions can be reduced and represented in ecological models for better comprehension. In this study, a spatially explicit population model was created using the RAMAS software package to simulate the past and future invasion dynamics of the eastern grey squirrel (Sciurus carolinensis) in the fragmented habitat in case study areas in Ireland. This invasive squirrel species causes economic damage by bark stripping forest crops and is associated with the decline of its native congener (S. vulgaris). Three combinations of demographic and dispersal parameters, which best matched the distribution of the species shortly after introduction, were used to simulate invasion dynamics. Future population expansion was modeled under scenarios of no control and two different management strategies: fatal culls and immunocontraceptive vaccination programmes. In the absence of control, the grey squirrel range is predicted to expand to the south and southwest of Ireland endangering internationally important habitats, vulnerable forest crops, and the native red squirrel. The model revealed that region-wide intensive and coordinated culls would have the greatest impact on grey squirrel populations. Control strategies consisting solely of immunocontraceptive vaccines, often preferred by public interest groups, are predicted to be less effective. Complete eradication of the grey squirrel from Ireland is not economically feasible and strategic evidence-based management is required to limit further range expansion. Ecological models can be used to choose between informed management strategies based on predicted outcomes.     

Effects of long-range taxis and population pressure on the range expansion of invasive species in heterogeneous environments

We consider a new model for biological invasions in periodic patchy environments, in which long-range taxis and population pressure are incorporated in the framework of reaction-diffusion-advection equations. We assume that long-range taxis is induced by a weighted integral of stimuli within a certain sensing range. Population pressure is incorporated in the diffusion coefficient that linearly increases with population density. We first analyze the model in the absence of population pressure and demonstrate how the sensing length of long-range taxis influences the range expansion pattern of invasive species and its rate of spread. The effects of population pressure are examined for both homogeneous and periodic patchy environments. For the homogeneous environment, an exact and explicit traveling wave solution and the spreading speed are obtained. For the periodic patchy environment, we find numerically that a population starting from any localized distribution evolves to a traveling periodic wave if the null solution of the RDA equation is locally unstable, and that the traveling wave speed significantly increases with increasing population pressure. Furthermore, the population pressure and taxis intensity synergistically enhance the spreading speed when they are increased together.     

Host range of a newly introduced parasitoid, Binodoxys communis among common aphid species in Hawaii

Binodoxys communis (Gahan) (Hymenoptera:Braconidae), a parasitoid of aphids originally from China, was introduced into Hawaii and evaluated in the laboratory for its ability to detect, accept, oviposit and develop in Aphis gossypii reared on two host plants, plus five other common aphid species. The parasitoid was able to detect all six aphid species and to successfully sting five species, with highest preference for those in the genus Aphis. Aphis species were highly suitable for parasitoid development. Other species were only marginally suitable. Parasitoids spent less time searching on plants of less acceptable aphids. Aphid defensive behaviors did not affect oviposition success, but did lengthen the parasitoid’s handling time of several aphid species. Host acceptance was positively correlated with host suitability, yet one unsuitable host was readily accepted for oviposition.     

Production of selected baculoviruses in newly established lepidopteran cell lines

Summary One key to the in vitro mass production of baculoviruses is the development of insect cell lines capable of producing high levels of extracellular virus (ECV) and/or occlusion bodies (OBs). For this study, 34 newly established cell lines from 10 lepidopteran species were screened for their ability to produce ECV and OBs from a variety of baculoviruses. The selected baculoviruses included: the alfalfa looper virus (AcMNPV); the celery looper virus (AfMNPV); the velvetbean caterpillar virus (AgMNPV), the bollworm virus (HzSNPV), the diamondback moth virus (PxMNPV), and the beet armyworm virus (SeMNPV). ECV titers were determined using TCID₅₀ assays (50% tissue culture infectivity dose), with the presence or absence of OBs being noted. For AcMNPV, 28 new cell lines were tested, with eight producing AcMNPV ECV titers of 1.1–47.3×10⁶ TCID₅₀/ml and 11 producing OBs. For AgMNPV, six new cell lines were tested, with all producing AgMNPV ECV titers of 3.5–62.3×10⁶ TCID₅₀/ml and generating OBs. For HzSNPV, four new cell lines were tested with three lines producing HzSNPV ECV titers of 1.4–5.0×10⁶TCID₅₀/ml, but none generating OBs. For PxMNPV, 10 new cell lines were tested with seven generating PxMNPV ECV titers of 4.7–232.6×10⁶TCID₅₀/ml and eight producing OBs. Lastly, using qualitative or semiquantitative methods, homologous cell lines were tested for AfMNPV and SeMNPV production, all of which produced OBs. Overall, many of the cell lines tested were found to produce OBs and generate moderate to high levels of ECVs of one or more baculoviruses. All programs and services of the USDA Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status or handicap.     

Annual growth rates in newly established populations of the butterfly Pararge aegeria

1. The likelihood of range changes in the event of climate change makes study of the foundation and establishment of populations of particular relevance and interest.
2. The butterfly Pararge aegeria has expanded its range in Britain over many decades. Since 1985, ten monitored sites in eastern England have been colonized and the pattern of population growth examined.
3. Geometric annual growth rates in the establishing populations were initially, on average, three- to fourfold but subsequently declined. The decline provides possible evidence that density-dependence limits final population densities, but other explanations are possible.     

昆虫界的“四不象”——一新建“螳目”昆虫简介

该文对 2 0 0 2年 5月建立的昆虫新目———螳目Mantophasmatodea作了简单介绍 ,并建议了该目之中名。该目是昆虫纲中最小的目 ,目前已知 2属 3种 ,分布于非洲     

Evaluation of machine learning methods for predicting eradication of aquatic invasive species

In the work, we evaluate the performance of machine learning approaches for predicting successful eradication of aquatic invasive species (AIS) and assess the extent to which eradication of an invasive species depends on the certain specified ecological features of the target ecosystem and/or features that characterize the planned intervention. We studied the outcomes of 143 planned attempts for eradicating AIS, where each attempt was described by ecological and eradication-strategy-related features of the target ecosystem. We considered several machine learning approaches to determine whether one could produce a classifier that accurately predicts weather an invasive species will be eradicated. To assess each learner’s performance, we examined its tenfold cross-validated prediction accuracy as well as the false positive rate, the F-measure, and the Area Under the ROC Curve. We also used Kaplan–Meier survival analysis to determine which features are relevant to predicting the time required for each eradication program. Across the five typical machine learning approaches, our analysis suggests that learners trained by the decision tree work well, and have the best performance. In particular, by examining the trained decision tree model, we found that if an occupied area was not large and/or containments of AIS dispersal were employed, the eradication of AIS was likely to be successful. We also trained decision tree models over only the ecological features and found that their performances were comparable with that of models trained using all features. As our trained decision tree models are accurate, decision makers can use them to estimate the result of the proposed actions before they commit to which specific strategy should be applied.     

Evaluating management options for aquatic invasive species: concepts and methods

In analyses that attempt to estimate the costs of species invasions, it has been typical to report the costs of management and/or to multiply per-unit costs by the number affected to arrive at a total. These estimates are of limited value for most policy questions. We start our discussion by recognizing that biological pollutants such as aquatic invasive species are like conventional pollutants in important ways and appeal to the well-developed literature on conventional pollution to guide our thinking into how best to conceptualize the problem. We use a standard pollution control framework to identify the margins over which costs and benefits should be estimated to guide wise decision-making. We then use examples from the literature to illustrate how transactions in related markets can be used to estimate the benefits of management. The roles of adaptation, mitigation, and species population growth have particular relevance and are highlighted. In the final section of the paper, we think through the conditions under which investing in genetic biocontrol methods would be economically justified.