Growth form and distribution of introduced plants in their native and non-native ranges in Eastern Asia and North America

There is a growing interest in understanding the influence of plant traits on their ability to spread in non-native regions. Many studies addressing this issue have been based on relatively small areas or restricted taxonomic groups. Here, we analyse a large data base involving 1567 plant species introduced between Eastern Asia and North America or from elsewhere to both regions. We related the extent of species distributions in each region to growth form and the distinction between upland and wetland habitats. We identified significant relationships between geographical distribution and plant traits in both native and exotic ranges as well as regional differences in the relationships. Range size was larger for herbaceous graminoids and forbs, especially annuals compared to perennials, than for woody species, and range size also was larger for plants of wetland compared to upland habitats. Distributions were more extensive in North America than in Eastern Asia, although native plants from both regions had broader distributions than non-natives, with exotics from elsewhere intermediate. Growth form and environment explained more of the variance in distribution of plants in North America than in Eastern Asia. The influence of growth form and habitat on distribution suggests that these traits might be related to tolerance of ecological conditions. In addition, the smaller extents of species in non-native compared to native areas suggest roles for dispersal limitation and adaptation to region-specific ecological conditions in determining distribution.     

Electromagnetic homeostasis and the role of low-amplitude electromagnetic fields on life organization

The appearance of endogenous electromagnetic fields in biological systems is a widely debated issue in modern science. The electrophysiological fields have very tiny intensities and it can be inferred that they are rapidly decreasing with the distance from the generating structure, vanishing at very short distances. This makes very hard their detection using standard experimental methods. However, the existence of fast-moving charged particles in the macromolecules inside both intracellular and extracellular fluids may envisage the generation of localized electric currents as well as the presence of closed loops, which implies the existence of magnetic fields. Moreover, the whole set of oscillatory frequencies of various substances, enzymes, cell membranes, nucleic acids, bioelectrical phenomena generated by the electrical rhythm of coherent groups of cells, cell-to-cell communication among population of host bacteria, forms the increasingly complex hierarchies of electromagnetic signals of different frequencies which cover the living being and represent a fundamental information network controlling the cell metabolism. From this approach emerges the concept of electromagnetic homeostasis: that is, the capability of the human body to maintain the balance of highly complex electromagnetic interactions within, in spite of the external electromagnetic noisy environment. This concept may have an important impact on the actual definitions of heal and disease.     

Essential oil variation and antioxidant capacity of Mentha pulegium populations and their relation to ecological factors

Mentha pulegium L. is an aromatic herb belonging to the Lamiaceae family, a wild plant which is distributed in different areas of Iran. In this research, we evaluated the variability of essential oil content and compositions of 12 M. pulegium populations. Essential oils were analyzed using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) methods. The essential oils content varied from 0.22 to 1.63% w/w within different populations. Twenty-nine compounds were identified which represent 83.4–98.7% of the total essential oil. The most significant essential oil compounds among the studied population were identified using the principal components analysis (PCA-biplot). According to the PCA-biplot, the major compounds were pulegone (2.5–51.7%), menthone (0.2–25.3%), limonene (0.0–35.4%), 1,8-cineol (0.0–33.4%), piperitenone oxide (0.2–55.2%), and trans-piperitone epoxide (0.0–28.5%). Besides, hierarchical cluster analysis indicated that the studied populations were classified into two main clusters based on the essential oil components. The canonical correspondence analysis (CCA) indicated that some environmental factors could influence the phytochemical constituents as well as the antioxidant activity. The temperature and altitude were effective environmental factors with regards to 1–8 cineol, limonene and menthone content, while average rainfall was the most effective factor with respect to trans-piperitone epoxide, piperitenone oxide, and pulegone content. Our results consequently showed that environmental factors had a significant effect on the essential oil content and its antioxidant activity in M. pulegium populations.     

Effect of temperature on woodwasp (Sirex noctilio F.) development and parasitism by the entomopathogenic nematode,Deladenus siricidicola

The woodwasp, Sirex noctilio, is a significant global pest of exotic pine plantations in the Southern Hemisphere and now threatens native pine forests in North America. Management in Australia relies on biocontrol using the nematode, Deladenus (= Beddingia) siricidicola (Bedding), which infects and sterilises females who then further disperse the nematode. This pest is spreading into warmer regions in Australia and South America and coupled with the threat of global climate change, there is uncertainty as to how increasing temperatures will affect the biocontrol program. S. noctilio within nematode-inoculated wood were reared at four temperatures (24, 25.3, 26.6 and 28 °C) to investigate the effects of elevated temperatures on wasp development (emergence time, sex ratio and size), development of eggs (number, size, and maturation) and infection by the nematode. At 24 °C, which reflects current field temperature, S. noctilio were bigger in size and all the eggs were normal and all were infected with nematodes. Modest rises in temperature reflecting climate change scenarios resulted in smaller sized S. noctilio, disrupted egg development and maturation, and lowered the nematode sterilisation rate in females. Reduced S. noctilio female body size and egg infection will likely compromise biocontrol by D. siricidicola in its current distribution, but disrupted egg development may act directly on the pest, limiting dispersal of S. noctilio into subtropical pine plantations and adaptation to climate change.     

Synergistic interactions between leaf beetle herbivory and fire enhance tamarisk (Tamarix spp.) mortality

The combined effects of herbivory and fire on plant mortality were investigated using prescribed burns of tamarisk (Tamarix ramosissima Lebed) exposed to herbivory by the saltcedar leaf beetle (Chrysomelidae: Diorhabda carinulata Desbrocher). Tamarix stands in the Humboldt Sink (NV, USA) were divided into three treatments: summer burn (August 2006), fall burn (October 2006) and control (unburned), and litter depth was manipulated to vary fire intensity within burn seasons. A gradient of existing herbivory impact was described with three plant condition metrics prior to fire: reduced proportions of green canopy, percent root crown starch sampled at the height of the growing season (August 2006), and percent root crown starch measured during dormancy (December 2006). August root crown starch concentration and proportion green canopy were strongly correlated, although the proportion green canopy predicted mortality better than August root crown starch. December root crown starch concentration was more depleted in unburned trees and in trees burned during the summer than in fall burn trees. Mortality in summer burned trees was higher than fall burned trees due to higher fire intensity, but December root crown starch available for resprouting in the spring was also lower in summer burned trees. The greatest mortality was observed in trees with the lowest December root crown starch concentration which were exposed to high fire intensity. Disproportionate changes in the slope and curvature of prediction traces as fire intensity and December starch reach reciprocal maximum and minimum levels indicate that beetle herbivory and fire intensity are synergistic.     

Distribution of plant functional types along gradients of disturbance intensity and resource supply in an agricultural landscape

Abstract. In this study, plant functional types are understood as groups of plants with similar biological traits displaying significant optima or maxima on a gradient plane of resource supply and disturbance intensity. The biological traits refer to expansion, vegetative regeneration, generative reproduction, dispersal and seed bank longevity. 129 vegetation samples were taken in an agricultural landscape in southwestern Germany, covering a wide range of terrestrial vegetation types – but with the exception of forests and wetlands. For each site, also soil data were recorded. Mean daily soil moisture was estimated with a simple model. Soil moisture, balanced nitrogen supply and available phosphorus were combined into a factor ‘resource supply’. In addition, disturbance intensity was estimated for each site. This factor was based on (1) frequency of disturbance, (2) disturbance depth below or above the soil surface, and (3) proportion of the area affected by a discrete disturbance event. 30 plant groups with similar biological characteristics resulted from a cluster analysis, based on a compilation of 19 biological traits for a regional species pool. Logistic regression on a gradient plane of disturbance intensity and resource supply yielded response curves for 28 groups. The dependent variable was defined as the probability of encountering all members of a group in a sample. 17 groups display a significant response curve on the gradient plane. Plants with a potential for long- range dispersal are concentrated on sites with low or high disturbance intensities (e.g. fallow land, fields, lawns). On sites with medium disturbance intensity (e.g. meadows) and low to medium resource supply, small-range dispersal predominates. There are no distinct trends concerning seed bank longevity. The potential for vertical and lateral expansion increases with decreasing disturbance intensity. Only at medium disturbance intensities does vertical expansion correlate positively with resource supply. Rapid detachment of daughter individuals occurs more often on productive sites than on less productive sites. Diversity of groups with similar biological traits is highest on sites with medium disturbance intensities.     

Reply to the first systematic response by the Global Footprint Network to criticism: A real debate finally?

We respond to a reaction of the Global Footprint Network/GFN on our 8-point criticism of the ecological footprint. We also refer to, and comment on, an associated debate in this journal between Giampietro and Saltelli, 2014a, Giampietro and Saltelli, 2014b, on the one hand, and Goldfinger et al. (2014), on the other. We conclude that criticism on the footprint is accumulating and coherent across the various studies and disciplines and among the different authors. This was the first time that Wackernagel/GFN systematically responded to our criticisms. Hence, our response contains several original elements and the resulting exchange can be seen to add value to the existing literature. It ultimately allows readers to better make up their mind about the different viewpoints on the ecological footprint.     

Deconstructing occupancy frequency distributions in stream insects: effects of body size and niche characteristics in different geographical regions

1. Occupancy frequency distributions (OFDs) are one means to study species distribution patterns, allowing the delineation of rare and common species. Very few studies have deconstructed entire assemblages by ecological or biological characteristics and subsequently examined OFDs in subgroups of species. 2. The effect of deconstruction of entire assemblages by niche breadth, niche position or body size classes on OFDs in stream insects in three drainage basins was examined. It was hypothesized that OFDs should not vary between different drainage basins, but they should be affected by deconstruction into different niche breadth, niche position or body size classes. 3. The OFDs were typically strongly right‐skewed in all drainage basins. The set of small‐sized species was strongly dominated by rare species, whereas the importance of rare species decreased with increasing body size. Further, while the OFDs of sets of species with marginal niche position or small niche breadth were strongly dominated by rare species, those of species with non‐marginal niche position or large niche breadth showed highly variable degrees of occupancy. The OFDs of non‐marginal species were even uniform in the entire data and one drainage basin, providing partial support to the a priori hypothesis. 4. Niche‐based explanations are likely to account for occupancies of marginal and small‐niched species, whereas the distributions of non‐marginal and broad‐niched species may be not only affected by niche‐based mechanisms but also by spatial dynamics. Deconstruction of OFDs by ecological and biological traits thus showed that the patterns may vary between different subgroups of species.     

Novel strategies for assessing and managing the risks posed by invasive alien species to global crop production and biodiversity

International actions to combat the threat posed by invasive alien species (IAS) to crops and biodiversity have intensified in recent years. The formulation of 15 guiding principles on IAS by the Convention on Biological Diversity (CBD) stimulated the International Plant Protection Convention (IPPC) to review its role in protecting biodiversity. IPPC standards now demonstrate clearly that the risks posed by any organism that is directly or indirectly injurious to cultivated or uncultivated plants can be assessed and managed under the IPPC. Since the IPPC, unlike the CBD, constitutes an international legal instrument recognised by the World Trade Organization, greater protection from the introduction of IAS is now available. However, phytosanitary measures can only be enacted if they can be justified by risk analysis and we outline some novel strategies to improve the assessment and management of the risks posed by IAS, highlighting some of the key challenges which remain.     

Bird sensitivity to disturbance as an indicator of forest patch conditions: An issue in environmental assessments

An Environmental Assessment (EA) is one of the steps within the Environmental Impact Assessment process. Birds are often used in EA to help decision makers evaluate potential human impacts from proposed development activities. A “sensitivity to human disturbance” index, created by Parker III et al. (1996) for all Neotropical species, is commonly considered an ecological indicator. However, this parameter was created subjectively and, for most species, there have been no rigorous field test to validate its effectiveness as such. Therefore, in this study, we aim to: (1) evaluate if, at the local scale, birds from forest patches in a human-modified landscape (HML) may differ in sensitivity from Parker's sensitivity classification; (2) evaluate the effectiveness of the species richness value at each sensitivity level as an ecological indicator; (3) gather information on how often and in which manner Parker's classification has been used in EA. To do so, bird sampling was performed in eight forest patches in a HML over one year. Then, we created a local sensitivity to disturbance using information about threat, endemism, spatial distribution and relative abundance of all species in the study area. We found that 37% of the forest birds showed different local sensitivity levels when compared with Parker's classification. Our results show that only the richness of high-sensitivity species from our local classification fitted the ecological indicator assumptions helping the environmental conditions evaluation of the studied patches. We conclude that species richness of each Parker's bird sensitivity levels do not necessarily perform as an ecological indicator at the local scale, and particularly in HML. Nevertheless, Parker's Neotropical bird sensitivity classification was used in 50% of EA we reviewed. In these, 76% assumed that it was an accurate ecological indicator of the local forest conditions for birds. The lack of clear criteria used in Parker's classification allows diverse interpretations by ornithologists, and there is no agreement about the ecological meaning of each sensitivity level and what environmental conditions each level may indicate of. Therefore, the use of Parker's classification in EA may jeopardize accurate interpretations of proposed anthropogenic impacts. Furthermore, because a bird species’ sensitivity often varies between locations, we argue that Parker's generalized classification of bird sensitivity should not be used as an indicator of forest environmental conditions in EA throughout HMLs in Neotropics. Rather, local bird ecological indices should be explored, otherwise, erroneous predictions of the anthropogenic impacts will continue to be common.