Wolfgang Nentwig

How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment

Recent comprehensive data provided through the DAISIE project (www.europe-aliens.org) have facilitated the development of the first pan-European assessment of the impacts of alien plants, vertebrates, and invertebrates – in terrestrial, freshwater, and marine environments – on ecosystem services. There are 1094 species with documented ecological impacts and 1347 with economic impacts. The two taxonomic groups with the most species causing impacts are terrestrial invertebrates and terrestrial plants. The North Sea is the maritime region that suffers the most impacts. Across taxa and regions, ecological and economic impacts are highly correlated. Terrestrial invertebrates create greater economic impacts than ecological impacts, while the reverse is true for terrestrial plants. Alien species from all taxonomic groups affect “supporting”, “provisioning”, “regulating”, and “cultural” services and interfere with human well-being. Terrestrial vertebrates are responsible for the greatest range of impacts, and these are widely distributed across Europe. Here, we present a review of the financial costs, as the first step toward calculating an estimate of the economic consequences of alien species in Europe.

Ecophysiology of spiders

A Cuticle, Temperature and Respiration.- I Chelicerate Cuticle Structure.- II Coloration and Chromes.- III Thermal and Water Relations.- IV Behavioural Temperature Regulation.- V Behavioural and Physiological Adaptations to Cold.- VI Respiratory System: Structure and Function.- VII Heart Rate and Physiological Ecology.- VIII Moulting Hormones.- B Glands, Silk and Webs.- I Glandular Aspects of Sexual Biology.- II Communication with Chemicals: Pheromones and Spiders.- III Spider Venoms and Their Effect.- IV Comparative Structure and Histochemistry of Silk-Producing Organs in Arachnids.- V Fine Structure and Function of Capture Threads.- VI Chemistry, Physical Properties, and Synthesis of Araneidae Orb Webs.- VII Ecological Aspects of Spider Webs.- C Feeding Ecology.- I Structure and Function of the Digestive Tract.- II Excretory Organs.- III The Prey of Spiders.- IV Feeding Ecology of Winter-Active Spiders.- V Kleptobiosis in Spiders.- VI Hunger and Starvation.- D Parasites.- I Nematode Parasites of Spiders.- II Spider-Hunting Sphecid Wasps.- III The Biology of Acroceridae (Diptera): True Endoparasitoids of Spiders.- E Environment and Life History.- I Life Cycles and Diapause.- II Dispersal: Ballooning and Other Mechanisms.- III Growth, Foraging and Reproductive Success.- IV The Biorhythms of Spiders.- References.

Disentangling the role of environmental and human pressures on biological invasions across Europe

The accelerating rates of international trade, travel, and transport in the latter half of the twentieth century have led to the progressive mixing of biota from across the world and the number of species introduced to new regions continues to increase. The importance of biogeographic, climatic, economic, and demographic factors as drivers of this trend is increasingly being realized but as yet there is no consensus regarding their relative importance. Whereas little may be done to mitigate the effects of geography and climate on invasions, a wider range of options may exist to moderate the impacts of economic and demographic drivers. Here we use the most recent data available from Europe to partition between macroecological, economic, and demographic variables the variation in alien species richness of bryophytes, fungi, vascular plants, terrestrial insects, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. Only national wealth and human population density were statistically significant predictors in the majority of models when analyzed jointly with climate, geography, and land cover. The economic and demographic variables reflect the intensity of human activities and integrate the effect of factors that directly determine the outcome of invasion such as propagule pressure, pathways of introduction, eutrophication, and the intensity of anthropogenic disturbance. The strong influence of economic and demographic variables on the levels of invasion by alien species demonstrates that future solutions to the problem of biological invasions at a national scale lie in mitigating the negative environmental consequences of human activities that generate wealth and by promoting more sustainable population growth.

Socioeconomic legacy yields an invasion debt

Globalization and economic growth are widely recognized as important drivers of biological invasions. Consequently, there is an increasing need for governments to address the role of international trade in their strategies to prevent species introductions. However, many of the most problematic alien species are not recent arrivals but were introduced several decades ago. Hence, current patterns of alien-species richness may better reflect historical rather than contemporary human activities, a phenomenon which might be called “invasion debt.” Here, we show that across 10 taxonomic groups (vascular plants, bryophytes, fungi, birds, mammals, reptiles, amphibians, fish, terrestrial insects, and aquatic invertebrates) in 28 European countries, current numbers of alien species established in the wild are indeed more closely related to indicators of socioeconomic activity from the year 1900 than to those from 2000, although the majority of species introductions occurred during the second half of the 20th century. The strength of the historical signal varies among taxonomic groups, with those possessing good capabilities for dispersal (birds, insects) more strongly associated with recent socioeconomic drivers. Nevertheless, our results suggest a considerable historical legacy for the majority of the taxa analyzed. The consequences of the current high levels of socioeconomic activity on the extent of biological invasions will thus probably not be completely realized until several decades into the future.

Will Threat of Biological Invasions Unite the European Union

New data on the extent of biological invasions pose major regulatory and political challenges to European institutions.

Degradation of the Cry1Ab protein within transgenic Bacillus thuringiensis corn tissue in the field.

Large quantities of Bacillus thuringiensis (Bt) corn plant residue are left in the field after harvest, which may have implications for the soil ecosystem. Potential impacts on soil organisms will also depend on the persistence of the Bt toxin in plant residues. Therefore, it is important to know how long the toxin persists in plant residues. In two field studies in the temperate corn‐growing region of Switzerland we investigated degradation of the Cry1Ab toxin in transgenic Bt corn leaves during autumn, winter and spring using an enzyme‐linked immunosorbent assay (ELISA). In the first field trial, representing a tillage system, no degradation of the Cry1Ab toxin was observed during the first month. During the second month, Cry1Ab toxin concentrations decreased to ≈ 20% of their initial values. During winter, there was no further degradation. When temperatures again increased in spring, the toxin continued to degrade slowly, but could still be detected in June. In the second field trial, representing a no‐tillage system, Cry1Ab toxin concentrations decreased without initial delay as for soil‐incorporated Bt plants, to 38% of the initial concentration during the first 40 days. They then continued to decrease until the end of the trial after 200 days in June, when 0.3% of the initial amount of Cry1Ab toxin was detected. Our results suggest that extended pre‐ and post‐commercial monitoring are necessary to assess the long‐term impact of Bt toxin in transgenic plant residues on soil organisms.

A unified classification of alien species based on the magnitude of their environmental impacts.

We present a method for categorising and comparing alien or invasive species in terms of how damaging they are to the environment, that can be applied across all taxa, scales, and impact metrics.

Plant extinctions and introductions lead to phylogenetic and taxonomic homogenization of the European flora

Human activities have altered the composition of biotas through two fundamental processes: native extinctions and alien introductions. Both processes affect the taxonomic (i.e., species identity) and phylogenetic (i.e., species evolutionary history) structure of species assemblages. However, it is not known what the relative magnitude of these effects is at large spatial scales. Here we analyze the large-scale effects of plant extinctions and introductions on taxonomic and phylogenetic diversity of floras across Europe, using data from 23 regions. Considering both native losses and alien additions in concert reveals that plant invasions since AD 1500 exceeded extinctions, resulting in (i) increased taxonomic diversity (i.e., species richness) but decreased phylogenetic diversity within European regions, and (ii) increased taxonomic and phylogenetic similarity among European regions. Those extinct species were phylogenetically and taxonomically unique and typical of individual regions, and extinctions usually were not continent-wide and therefore led to differentiation. By contrast, because introduced alien species tended to be closely related to native species, the floristic differentiation due to species extinction was lessened by taxonomic and phylogenetic homogenization effects. This was especially due to species that are alien to a region but native to other parts of Europe. As a result, floras of many European regions have partly lost and will continue to lose their uniqueness. The results suggest that biodiversity needs to be assessed in terms of both species taxonomic and phylogenetic identity, but the latter is rarely used as a metric of the biodiversity dynamics.

Effects of transgenic Bt corn litter on the earthworm Lumbricus terrestris

A 200‐day study was carried out to investigate the impact of transgenic Bacillus thuringiensis (Bt) corn on immature and adult Lumbricus terrestris in the field and in the laboratory. Another objective of this study was to develop test methods that could be used for standard testing of the impact of transgenic plants on different earthworm species in the field and in the laboratory. For this purpose two different experiments were involved, a laboratory experiment with adult L. terrestris and a field experiment with immature L. terrestris. No lethal effects of transgenic Bt corn on immature and adult earthworms were observed. Immature L. terrestris in the field had a very similar growth pattern when fed either (Bt+) or (Bt−) corn litter. No significant differences in relative weights of (Bt+) and (Bt−) corn‐fed adult L. terrestris were observed during the first 160 days of the laboratory trial, but after 200 days adult L. terrestris had a significant weight loss of 18% of their initial weight when fed (Bt+) corn litter compared to a weight gain of 4% of the initial weight of (Bt−) corn‐fed earthworms. Further studies are necessary to see whether or not this difference in relative weight was due to the Bt toxin or other factors discussed in the study. Degradation of Cry1Ab toxin in corn residues was significantly slower in the field than at 10 °C in the laboratory. Enzyme‐linked immunosorbent assay results indicated that earthworms in both experiments were exposed to the Bt toxin throughout the whole experimental time.

Alien Terrestrial Invertebrates of Europe

Unlike other groups of animals and plants, no checklist of alien terrestrial invertebrates was available in any of the European countries until recently. Since 2002, such checklists were successively provided by Austria (Essl and Rabitsch 2002), Germany (Geiter et al. 2002), the Czech Republic (Sefrova and Lastu vka 2005), Scandinavia (NOBANIS 2007), the United Kingdom (Hill et al. 2005), Switzerland (Wittenberg 2006) and Israel (Roll et al. 2007). However, most European regions remained uncovered and, furthermore, comparisons between the existing lists were inherently difficult because they used different definitions of alien. Thus, estimating the importance of terrestrial alien invertebrates at the European level remained impossible, mostly because of poor taxonomic knowledge existed for several groups. By gathering taxonomists and ecologists specialised on most invertebrate taxa together with collaborators working at the national level in 35 European countries, the DAISIE project intended to fill this gap. However, a lack of European expertise in some taxonomic groups did not allow coverage of all the terrestrial invertebrates with the same level of precision. Data on insects were more reliable than those of other taxa, and consequently the analyses presented below will mostly refer to this group.