Long-term Developments in Ecological Rehabilitation of the Main Distributaries in the Rhine Delta: Fish and Macroinvertebrates

Significant anthropogenic pressure in the Dutch part of the River Rhine is present from the 12th century. River engineering and water pollution were the main stress factors for flora and fauna. From the middle of the 20th century measures were taken to reduce water pollution. Recently, from 1987 onwards, these activities were put into a wider context of ecological river rehabilitation. Effects of improvements on fish and macroinvertebrates in the main distributaries in the Rhine delta are reviewed. The conclusions are that (a) most of the alterations in the Rhine delta are irreversible due to hard socio-economic boundary conditions (e.g. safety, navigation); (b) chances for the development of riverine biotopes have therefore to be found in the forelands and not in the main channels of the Rhine delta; (c) further reduction of pollutants, especially thermal pollution, is needed to help original species to colonise the Rhine delta again; (d) non-indigenous species clearly leave a mark on recolonisation possibilities of original species.     

The worldwide transfer of ants: geographical distribution and ecological invasions

Aim This is the first comprehensive account of the biogeography of ants transferred and at least temporarily established outside their native habitat. Location Using museum and literature records, I established the distributions of transferred ant species. Methods I used taxonomic and functional groups to assess how geographical spread as a transferred species is affected by taxonomy and life history. Results 147 ant species in forty-nine genera have been recorded outside of their native habitat. The proportion of transferred ants is similar to the number of genera and species in each subfamily. The species-rich subfamily Myrmicinae contains nearly 50% of all transferred species, while many of the species-poor subfamilies have absolutely no transferred species. A disproportionate high number of transferred ants originate from the Neotropical and Oriental biogeographic regions. The Pacific Islands are the recipients of the most transferred ant species. Most transferred ants belong to the CRYPTIC, OPPORTUNIST, and GENERALIZED MYRMICINE functional groups, while there are no recorded transfers of army ants or leaf-cutting ants. Both invasive and human commensal ‘tramp’ ant species are nonrandom subsets of transferred ants. Main conclusions ‘Tramp’ species and invasive species tend to have widespread geographical distributions, and share life history characteristics including queen number, nest structure, and foraging behaviour. Combining observations of functional groups and biogeography may lead to a better understanding of the factors contributing to the spread of transferred species.     

Absence of evidence is not evidence of absence: Feral pigs as vectors of soil‐borne pathogens

Invasive soil‐borne pathogens are a major threat to forest ecosystems worldwide. The newly discovered soil pathogen, Phytophthora ‘taxon Agathis’ (PTA), is a serious threat to endemic kauri (Agathis australis: Araucariaceae) in New Zealand. This study examined the potential for feral pigs to act as vectors of PTA. We investigated whether snouts and trotters of feral pigs carry soil contaminated with PTA, and using these results determined the probability that feral pigs act as a vector. We screened the soil on trotters and snouts from 457 pigs for PTA using various baiting techniques and molecular testing. This study detected 19 species of plant pathogens in the soil on pig trotters and snouts, including a different Phytophthora species (Phytophthora cinnamomi). However, no PTA was isolated from the samples. A positive control experiment showed a test sensitivity of 0–3% for the baiting methods and the data obtained were used in a Bayesian probability modelling approach. This showed a posterior probability of 35–90% (dependent on test sensitivity scores and design prevalence) that pigs do vector PTA and estimated that a sample size of over 1000 trotters would be required to prove a negative result. We conclude that feral pigs cannot be ruled out as a vector of soil‐based plant pathogens and that there is still a high probability that feral pigs do vector PTA, despite our negative results. We also highlight the need to develop a more sensitive test for PTA in small soil samples associated with pigs due to unreliable detection rates using the current method.     

Perches and elevated platforms in commercial broiler farms: use and effect on walking ability,incidence of tibial dyschondroplasia and bone mineral content

Modern fast-growing broilers spend excessive periods resting and their activity further decreases with age. Inactivity has been suggested to increase impaired gait and the incidence of leg disorders. Tibial dyschondroplasia (TD) is a common leg pathology in broilers. A more complex environment might facilitate more activity and improve leg health. Perches or elevated platforms bring variety to broilers’ environment and could motivate more locomotion. This study examined the impact of perches and elevated platforms on walking ability, the occurrence of TD and level of bone ash and mineral contents. The investigation was performed on four commercial broiler farms throughout six consecutive batches with platforms and four to five with perches. On each farm at least two separate houses were included, enabling the comparison of furnished flocks to control flocks during each batch. Plastic slats with ramp access elevated by 30 cm or wooden perches of 10 and 30 cm height were offered in the furnished house. Farmers recorded the platform and perch usage twice a week with a five-point scale. Gait was scored before slaughter on a six-point scale according to the Welfare Quality® assessment protocol for poultry. The severity of TD was determined using a four-point scale on farm from all birds gait scored as 3 and at slaughter from 200 birds/flock. Farmers estimated 50% to 100% of the platforms to be occupied in all flocks throughout the entire growing period. Only single birds were perching, thus perch structures were constantly evaluated to be empty. Due to the low use, the perch-equipped houses were excluded when analysing bone content, walking ability and TD. On average, 30% of the tested birds exhibited gait score ⩾3. Younger scoring age resulted in a lower mean gait score and a lower percentage of scores 3 and 4 to 5. Overall, 2.3% of the birds examined at slaughter and 3.5% of the birds with gait score 3 were affected by TD. Leg health was better in birds with access to platforms: mean gait score, the percentage of birds scoring 3, and TD percentage and severity were lower in birds in platform-equipped houses. Elevated structures such as platforms, offering additional possibilities for locomotion to broilers seem to improve their leg health.     

Antimycotic activity of Melaleuca alternifolia essential oil and its major components

AIMS: The aim of this study was to analyse the antimycotic properties of Melaleuca alternifolia essential oil (tea tree oil, TTO) and its principal components and to compare them with the activity of 5-fluorocytosine and amphotericin B. METHODS AND RESULTS: The screening for the antimycotic activity was performed by serial twofold dilutions in Roswell Park Memorial Institute medium with the inclusion of Tween-80 (0.5%). TTO and terpinen-4-olo were the most active compounds. CONCLUSIONS: The majority of the organisms were sensitive to the essential oil, with TTO and terpinen-4-olo being the most active oils showing antifungal activity at minimum inhibitory concentration values lower than other drugs. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides a sample large enough to determine the antifungal properties of TTO and terpinen-4-olo and suggests further studies for a possible therapeutic use.     

Phoresy in animals: review and synthesis of a common but understudied mode of dispersal

Phoresy is a type of interaction in which one species, the phoront, uses another species, the dispersal host, for transportation to new habitats or resources. Despite being a widespread behaviour, little is known about the ecology and evolution of phoresy. Our goal is to provide a comprehensive review of phoretic dispersal in animals and to bring renewed attention to this subject. We surveyed literature published between 1900 and 2020 to understand the extent of known higher-level taxonomic diversity (phyla, classes, and orders) and functional aspects of animals that use phoretic dispersal. Species dispersing phoretically have been observed in at least 13 animal phyla, 25 classes, and 60 orders. The majority of known phoronts are arthropods (Phylum Euarthropoda) in terrestrial habitats, but phoronts also occur in freshwater and marine environments. Marine phoronts may be severely under-represented in the literature due to the relative difficulty of studying these systems. Phoronts are generally small with low mobility and use habitats or resources that are ephemeral and/or widely dispersed. Many phoronts are also parasites. In general, animals that engage in phoresy use a wide variety of morphological and behavioural traits for locating, attaching to, and detaching from dispersal hosts, but the exact mechanisms behind these activities are largely unknown. In addition to diversity, we discuss the evolution of phoresy including the long-standing idea that it can be a precursor to parasitism and other forms of symbioses. Finally, we suggest several areas of future research to improve our understanding of phoresy and its ecological and evolutionary significance.     

Predicting and explaining plant invasions through analysis of source area floras: some critical considerations

Comparing species that become invasive with others from the same regional species pool that do not invade raises several issues about the accuracy of analyses attempting to define the determinants of invasiveness. The delimitation of the source area and deciding which species group(s) to include are especially relevant in analyses focusing on species originating in Europe. Historical patterns of immigration of alien species into Europe must be considered since European floras comprise a complex mix of native species, historical introductions (archaeophytes) and relative newcomers (neophytes). We make three main points: (1) Archaeophytes (species introduced to Europe before the discovery of America) differ from natives in a number of traits and in historical association with people; it is misleading to lump archaeophytes with native taxa. (2) Taxa from climatically and geographically different regions, representing distinct floristic geoelements, need to be treated separately, and not as a homogenous pool of potential invaders. Restricting the source species pool to native taxa with comparable phytogeographical characteristics reduces the variation associated with chance of dispersal by humans from the source area. (3) For prediction, a clear distinction should be made between accuracy (the proportion of those found to be alien that were also predicted to be there) and reliability (or predictive value, the proportion of those predicted to become aliens that do so). Information accumulated over centuries by botanists in Central Europe provides an excellent opportunity to deal with these issues and avoid spurious results. To illustrate these issues, we revisit a recently published study of Central‐European plant species as invaders in two Argentinean provinces ( Prinzing et al., 2002 ) to explore and demonstrate the implications of the above points. We hope that future studies will build on these points to achieve more reliable predictions.     

Cross-species transfer of viruses: implications for the use of viral vectors in biomedical research, gene therapy and as live-virus vaccines

All living organisms are continuously exposed to a plethora of viruses. In general, viruses tend to be restricted to the natural host species which they infect. From time to time viruses cross the host-range barrier expanding their host range. However, in very rare cases cross-species transfer is followed by the establishment and persistence of a virus in the new host species, which may result in disease. Recent examples of viruses that have crossed the species barrier from animal reservoirs to humans are hantavirus, haemorrhagic fever viruses, arboviruses, Nipah and Hendra viruses, avian influenza virus (AI), monkeypox virus, and the SARS-associated coronavirus (SARS-CoV). The opportunities for cross-species transfer of mammalian viruses have increased in recent years due to increased contact between humans and animal reservoirs. However, it is difficult to predict when such events will take place since the viral adaptation that is needed to accomplish this is multifactorial and stochastic. Against this background the intensified use of viruses and their genetically modified variants as viral gene transfer vectors for biomedical research, experimental gene therapy and for live-vector vaccines is a cause for concern. This review addresses a number of potential risk factors and their implications for activities with viral vectors from the perspective of cross-species transfer of viruses in nature, with emphasis on the occurrence of host-range mutants resulting from either cell culture or tropism engineering. The issues are raised with the intention to assist in risk assessments for activities with vector viruses.     

Antimicrobial activity and the major components of the essential oil of Plectranthus cylindraceus

AIMS: The traditional uses of the aerial parts of fresh Plectranthus cylindraceus by the Dhofaris in Oman were investigated on the basis of antimicrobial properties and composition of its herb oil. METHODS AND RESULTS: The minimal inhibitory concentration (MIC) values of the herb oil of P. cylindraceus against human pathogenic bacteria and yeast were assessed using the broth microdilution method, and the percentage growth inhibition of fungi was determined according to the poisoned food technique. The oil exhibited good activity against Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis and Candida albicans with MIC values in the range of 7.8-62.5 microg ml(-1) and also inhibited the growth of Microsporum canis, Microsporum gypseum, Trichophyton rubrum, Alternaria alternata, Bipolaris sp., Curvularia lunata, Fusarium oxysporum and Stemphylium solani for about a week at 250 microg ml(-1). The two most abundant components of the oil were identified as carvacrol (46.8%) and alpha-terpinolene (18.2%) based on gas chromatography-mass spectra (GC-MS) and 13C nuclear magnetic resonance (NMR) analyses. CONCLUSIONS: The oil has a pleasant odour and showed broad spectrum antimicrobial activity. Such bioactivity could be attributed in part to carvacrol. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has demonstrated the broad spectrum antimicrobial activity of the herb oil of P. cylindraceus as well as the organic composition of this plant extract. This study provides scientific insight into the ancient practice of utilizing P. cylindraceus as a fragrant disinfectant.     

Metabarcoding improves detection of eukaryotes from early biofouling communities: implications for pest monitoring and pathway management

In this experimental study the patterns in early marine biofouling communities and possible implications for surveillance and environmental management were explored using metabarcoding, viz. 18S ribosomal RNA gene barcoding in combination with high-throughput sequencing. The community structure of eukaryotic assemblages and the patterns of initial succession were assessed from settlement plates deployed in a busy port for one, five and 15 days. The metabarcoding results were verified with traditional morphological identification of taxa from selected experimental plates. Metabarcoding analysis identified > 400 taxa at a comparatively low taxonomic level and morphological analysis resulted in the detection of 25 taxa at varying levels of resolution. Despite the differences in resolution, data from both methods were consistent at high taxonomic levels and similar patterns in community shifts were observed. A high percentage of sequences belonging to genera known to contain non-indigenous species (NIS) were detected after exposure for only one day.     

Founding events in species invasions: genetic variation, adaptive evolution, and the role of multiple introductions

Invasive species are predicted to suffer from reductions in genetic diversity during founding events, reducing adaptive potential. Integrating evidence from two literature reviews and two case studies, we address the following questions: How much genetic diversity is lost in invasions? Do multiple introductions ameliorate this loss? Is there evidence for loss of diversity in quantitative traits? Do invaders that have experienced strong bottlenecks show adaptive evolution? How do multiple introductions influence adaptation on a landscape scale? We reviewed studies of 80 species of animals, plants, and fungi that quantified nuclear molecular diversity within introduced and source populations. Overall, there were significant losses of both allelic richness and heterozygosity in introduced populations, and large gains in diversity were rare. Evidence for multiple introductions was associated with increased diversity, and allelic variation appeared to increase over long timescales (~100 years), suggesting a role for gene flow in augmenting diversity over the long‐term. We then reviewed the literature on quantitative trait diversity and found that broad‐sense variation rarely declines in introductions, but direct comparisons of additive variance were lacking. Our studies of Hypericum canariense invasions illustrate how populations with diminished diversity may still evolve rapidly. Given the prevalence of genetic bottlenecks in successful invading populations and the potential for adaptive evolution in quantitative traits, we suggest that the disadvantages associated with founding events may have been overstated. However, our work on the successful invader Verbascum thapsus illustrates how multiple introductions may take time to commingle, instead persisting as a ‘mosaic of maladaptation’ where traits are not distributed in a pattern consistent with adaptation. We conclude that management limiting gene flow among introduced populations may reduce adaptive potential but is unlikely to prevent expansion or the evolution of novel invasive behaviour.     

Molecular systematics and population genetics of biological invasions: towards a better understanding of invasive species management

The study of population genetics of invasive species offers opportunities to investigate rapid evolutionary processes at work, and while the ecology of biological invasions has enjoyed extensive attention in the past, the recentness of molecular techniques makes their application in invasion ecology a fairly new approach. Despite this, molecular biology has already proved powerful in inferring aspects not only relevant to the evolutionary biologist but also to those concerned with invasive species management. Here, we review the different molecular markers routinely used in such studies and their application(s) in addressing different questions in invasion ecology. We then review the current literature on molecular genetic studies aimed at improving management and the understanding of invasive species by resolving of taxonomic issues, elucidating geographical sources of invaders, detecting hybridisation and introgression, tracking dispersal and spread and assessing the importance of genetic diversity in invasion success. Finally, we make some suggestions for future research efforts in molecular ecology of biological invasions.     

Staged invasions across disparate grasslands: effects of seed provenance,consumers and disturbance on productivity and species richness

Exotic plant invasions are thought to alter productivity and species richness, yet these patterns are typically correlative. Few studies have experimentally invaded sites and asked how addition of novel species influences ecosystem function and community structure and examined the role of competitors and/or consumers in mediating these patterns. We invaded disturbed and undisturbed subplots in and out of rodent exclosures with seeds of native or exotic species in grasslands in Montana, California and Germany. Seed addition enhanced aboveground biomass and species richness compared with no‐seeds‐added controls, with exotics having disproportionate effects on productivity compared with natives. Disturbance enhanced the effects of seed addition on productivity and species richness, whereas rodents reduced productivity, but only in Germany and California. Our results demonstrate that experimental introduction of novel species can alter ecosystem function and community structure, but that local filters such as competition and herbivory influence the magnitude of these impacts.     

茂名油页岩废渣场土壤动物的种类组成及其多样性

研究不同生态改造状况下,茂名市油页岩废渣场的土壤动物种类组成及其多样性.研究样地分别设在1985年形成并同时植树造林和1992年形成后刚开始种树的两个废渣场（南排和北排）上.研究的土壤动物包括手拣法和干漏斗法收集的以大、中型为主的类群.动物分类至科或属,只有很小的部分分类至目（如唇足纲）或分类至种（如等足目等）.本研究共获得11164号标本（分属27目,110科-属）,并根据此样本进行分析：在土壤动物种类组成方面,分别在群落和类群两个层面上,分析样地间的差异;在土壤动物的多样性方面,除用Shannon指数（H′）进行样地间种类多样性比较外,还用以类群为基础的DGg指数,及以种类为基础的DGs指数,分别进行样地间的比较.主要结果：（1）在只有幼树的北排废渣场,获得土壤动物9目33科属;在南排废渣场中,经过约20a自然恢复的草地及种植约20a的大叶相思林地,分别获得23目67科属和23目61科属.（2）以种类为基础的DGs指数,3个样地分别为4.0、17.7和16.7.显示出北排的土壤动物种类组成简单,多样性很低;南排的两个样地,土壤动物的种类组成都较复杂,多样性较高而且很相近.但是,（3）以类群为基础的DGg指数,则南排的两个样地可分高低：大叶相思林为7.75,稍高于草地的7.20;此外,作为环境质量的甲螨指数（甲螨个体数/蜱螨类总个体数）,也是前者（0.93）高于后者（0.73）.因此,从实际上看,人工纯林对土壤改造效果应比草地要好一些,但还不是最理想的.     

Alien invasions in aquatic ecosystems: Toward an understanding of brook trout invasions and potential impacts on inland cutthroat trout in western North America

Experience from case studies of biologicalinvasions in aquatic ecosystems has motivated aset of proposed empirical rules forunderstanding patterns of invasion and impactson native species. Further evidence is neededto better understand these patterns, andperhaps contribute to a useful predictivetheory of invasions. We reviewed the case ofbrook trout (Salvelinus fontinalis)invasions in the western United States andtheir impacts on native cutthroat trout (Oncorhynchus clarki). Unlike many biologicalinvasions, a considerable body of empiricalresearch on brook trout and cutthroat trout isavailable. We reviewed life histories of eachspecies, brook trout invasions, their impactson cutthroat trout, and patterns and causes ofsegregation between brook trout and cutthroattrout. We considered four stages of theinvasion process: transport, establishment,spread, and impacts to native species. Most ofthe research we found focused on impacts. Interspecific interactions, especiallycompetition, were commonly investigated andcited as impacts of brook trout. In many casesit is not clear if brook trout invasions have ameasurable impact. Studies of speciesdistributions in the field and a variety ofexperiments suggest invasion success of brooktrout is associated with environmental factors,including temperature, landscape structure,habitat size, stream flow, and humaninfluences. Research on earlier stages ofbrook trout invasions (transport,establishment, and spread) is relativelylimited, but has provided promising insights. Management alternatives for controllingbrook trout invasions are limited, and actions tocontrol brook trout focus on direct removal,which is variably successful and can haveadverse effects on native species. Themanagement applicability of research has beenconfounded by the complexity of the problem andby a focus on understanding processes atsmaller scales, but not on predicting patternsat larger scales. In the short-term, animproved predictive understanding of brooktrout invasions could prove to be most useful,even if processes are incompletely understood. A stronger connection between research andmanagement is needed to identify more effectivealternatives for controlling brook troutinvasions and for identifying managementpriorities.     

Evaluation and application of methods for biological assessment of streams: summary of papers

The false mussel Mytilopsis adamsi, originally described from the Pacific coast of Panama, is reported for the first time as an introduced species in the Urías estuary and an adjacent shrimp farm, on the Pacific coasts of Mexico. In the 19th century, this species was transported from the Pacific coast of Panama, reaching the Indo-Pacific Ocean, but it had not been previously reported in other coasts of the American Pacific. Its recent and irregular presence in this small estuary near shore the Mazatlán harbor and an adjacent shrimp farm suggests that the species was introduced into the area but it cannot still be considered as a harmful invader. The presence of the species in the shrimp farm may indicate that it was introduced along with shrimp stocks from Central America, although its passive transportation to the estuary via ballast water or attached to hulls is not discounted.     

Insecticidal and acetylcholinesterase inhibitory activities of Achillea biebersteinii essential oil and its nanoemulsion and major monoterpenes against Tribolium castaneum

Essential oil (EO) was hydrodistilled from Achillea biebersteinii and analyzed using gas chromatography–flame ionization detection (GC–FID) and (GC–MS). Three monoterpenes, α-terpinene, p-cymene, and camphor were isolated as the main terpenes in the EO. Oil-in-water nanoemulsion (particle size 52.7 ± 4.4 nm) was prepared and characterized from EO through a hydrothermal approach. The EO products caused insecticidal effects and altered F₁ progeny of the red flour beetle, Tribolium castaneum (Herbst) in a dose and exposure time-dependent manner. The nanoemulsion was superior in bioactivity, followed EO. At 12.5 µl/cm², nanoemulsion and EO caused 100% mortality of the second larvae after 4 days of exposure with reduction of F₁ progeny of 100.0 and 89.2%, respectively. At 50.0 µl/cm², percentage mortality and reduction in progeny of EO products ranged between (61.4–100%) and (53.0–100%), respectively. Upon fumigation, nanoemulsion at 10 µl/L air caused 100% mortality of the second larvae after 4 days of exposure. At 20 µl/L air and 4 days after treatment, percentage mortality with the remainder botanicals ranging between 64.7 and 100. LC₅₀′s of products after 48 h exposure ranging between 6.7 and 58.1 µg/cm² in insecticidal bioassay, and between 3.6 and 26.3 µl/L upon fumigation. Botanicals caused a remarkable inhibition of acetylcholinesterase activity (AChE), where nanoemulsion (IC₅₀ = 14.22 mM), EO (IC₅₀ = 35.12 mM) and camphor (IC₅₀ = 23.93 mM) were superior as AChE inhibitors. There is a potential for using of A. biebersteinii EO, its nanoemulsion and monoterpenes as natural grain protectants after the required toxicological investigations.