Phytophagous Invertebrates Research Articles

Macroevolutionary analyses point to a key role of hosts in diversification of the highly speciose eriophyoid mite superfamily

The superfamily Eriophyoidea includes >5000 named species of very small phytophagous mites. As for many groups of phytophagous invertebrates, factors responsible for diversification of eriophyoid mites are unclear. Here, we used an inferred phylogeny of 566 putative species of eriophyoid mites based on fragments of two mitochondrial genes and two nuclear genes to examine factors associated with their massive evolutionary diversification through time. Our dated phylogeny indicates a Carboniferous origin for gymnosperm-associated Eriophyoidea with subsequent diversification involving multiple host shifts to angiosperms—first to dicots, and then to monocots or shifts back to gymnosperms—beginning in the Cretaceous period when angiosperms diverged. Speciation rates increased more rapidly in the Eriophyidae + Diptilomiopidae (mostly infesting angiosperms) than in the Phytoptidae (mostly infesting gymnosperms). Phylogenetic signal, speciation rates, dispersal and vicariance results combined with inferred topologies show that hosts played a key role in the evolution of eriophyoid mites. Speciation constrained by hosts was probably the main driver behind eriophyoid mite diversification worldwide. We demonstrate monophyly of the Eriophyoidea, whereas all three families, most subfamilies, tribes, and most genera are not monophyletic. Our time-calibrated tree provides a framework for further evolutionary studies of eriophyoid mites and their interactions with host plants as well as taxonomic revisions above the species level.

Phytophagous invertebrates that damage orchids in gardens of western Tabasco, Mexico

Objective: To record six species of invertebrates that damage orchids in gardens in the western area of the state of Tabasco, Mexico. Methodology: As part of the project "Fauna associated with plants cultivated in the south-southeast region of Mexico", non-systematic collections of invertebrates that were observed damaging orchids were made in three gardens in the western part of the state of Tabasco. The invertebrates were identified through descriptions and taxonomic keys. Results: Four species of insects of the order Coleoptera and two species of mollusks of the class Gastropoda are recorded. The insects are: (1) Diabrotica adelpha Harold (Chrysomelidae), (2) Stethobaris sp. (Curculionidae), (3) Cyclocephala guttata Bates (Scarabaeidae), these three damaging flowers of Brassavola nodosa (L.) Lindley; and (4) Stethobaroides nudiventris Champion (Curculionidae) damaging flowers of Catasetum integerrimum Hook. The mollusks are (1) Subulina octona (Bruguière) (Subulinidae) scraping leaves of Gongora leucochila Lem., Phalaenopsis sp. and C. integerrimum, and (2) Sarasinula plebeia (P.Fischer) (Veronicellidae) damaging leaves of C. integerrimum. Study limitations: It was not possible to specifically identify one of the insect species (Stethobaris sp.) and one of the damaged orchid species (Phalaenopsis sp). Conclusions: This study contributes to the knowledge of invertebrates that damage orchids in Mexico, and is a basis for future studies to determine the impact and importance of these organisms in the conservation and cultivation of orchids in this area of ​​Tabasco.

Influence of Structure of Detrital Food Webs on Fusarium Head Blight of Winter Wheat

Conventional methods for Fusarium head blight (FHB) control are ineffective. A better understanding of the mechanisms linking the abundance of Fusarium species in soil before winter wheat flowering and mycotoxin content in mature grain may help to improve the effectiveness of methods for FHB control. In this study, we established a field experiment aimed to trace the impact of three types of organic mulch with different C:N ratios on the structure of detrital food webs and the manifestation of winter wheat FHB. T2-toxin content in grain was significantly higher in N-poor treatment (52.1 ± 0.2 µg g−1) compared to N-rich treatment (40.4 ± 1.6 µg g−1). The structure of detrital food webs in the studied treatments changed significantly after mulch addition; the abundance of soil saprophages and mycophages increased up to 50%. Based on the results of mixed-effects modeling, the abundance of herpetobionts and soil mesofauna were positively associated with an increase in Fusarium biomass in grain. The increase in the content of T2-toxin in the grain was associated with an increase in the abundance of earthworms and phytophagous macrofauna in the soil. Results suggest the existence of a previously undescribed mechanism for FHB infection by transfer of pathogenic spores by soil invertebrates, while the content of mycotoxins in grain can be triggered by the grazing activity of soil phytophagous invertebrates.

Diversity of invertebrates under insecticide and biopesticide treatments in Brinjal agroecosystem

In an agroecosystem, knowledge of population ecology of invertebrates is of utmost importance to understand various relationships between crop plants, insects and its natural enemies. The present study was conducted to observe the effect of different biopesticides and insecticides on insect fauna in brinjal crop. Results revealed occurrence of 15 species of phytophagous arthropods belonging to five orders, Hemiptera, Coleoptera, Lepidoptera, Orthoptera and Succineidae, being highest from order Hemiptera. Similarly, 12 species of predators belonging to six orders (Araneae, Diptera, Dictyoptera, Neuroptera, Odonata and Coleoptera) were reported being highest in Coleoptera. Lower phytophagous population was recorded in insecticide treated fields as compared to biopesticides and control fields. However, higher predator population was recorded in biopesticide treated fields as compared to insecticide treatments as evidenced by calculation of diversity indices. Thus, the use of biopesticides is the best eco-friendly alternative that reduces phytophagous invertebrate population and encourages population of natural enemies.

A micronucleus assay detects genotoxic effects of herbicide exposure in a protected butterfly species

Lycaena dispar Hawort (Lepidoptera: Lycaenidae), a protected butterfly, is declining in Europe, but it thrives in rice fields in northern Italy. Here, agrochemical usage could threaten its long-term survival. We investigated, by micronucleus (MN) assay, the genotoxic effect of glyphosate, a common herbicide, on L. dispar larvae. Micronuclei (MNi) are DNA fragments separated from the main nucleus and represent the result of genomic damage that has been transmitted to daughter cells. In a control/treatment experiment, we extracted epithelial cells from last-instar larvae fed with Rumex spp. plants sprayed with a solution containing 3.6 g/L of glyphosate, and from larvae fed with unsprayed plants. MNi and other chromosomal aberrations—nuclear buds (NBUDs) and bi-nucleated cells—were then scored in 1000 cells/subject. Significant differences were found between glyphosate-exposed and control groups in terms of MNi and total genomic damage, but not in terms of NBUDs or bi-nucleated cells. We reported a possible genomic damage induced by glyphosate on larvae of L. dispar. For the first time, a MN assay was used in order to evaluate the genomic damage on a phytophagous invertebrate at the larval stage. Increased levels of MNi reflect a condition of genomic instability that can result in reduced vitality and in an increased risk of local extinction. Therefore, farmland management compatible with wildlife conservation is needed.

Altered trophic interactions in warming climates: consequences for predator diet breadth and fitness.

Species interactions are central in predicting the impairment of biodiversity with climate change. Trophic interactions may be altered through climate-dependent changes in either predator food preferences or prey communities. Yet, climate change impacts on predator diet remain surprisingly poorly understood. We experimentally studied the consequences of 2°C warmer climatic conditions on the trophic niche of a generalist lizard predator. We used a system of semi-natural mesocosms housing a variety of invertebrate species and in which climatic conditions were manipulated. Lizards in warmer climatic conditions ate at a greater predatory to phytophagous invertebrate ratio and had smaller individual dietary breadths. These shifts mainly arose from direct impacts of climate on lizard diets rather than from changes in prey communities. Dietary changes were associated with negative changes in fitness-related traits (body condition, gut microbiota) and survival. We demonstrate that climate change alters trophic interactions through top-predator dietary shifts, which might disrupt eco-evolutionary dynamics.

Microbial control of phytophagous invertebrate pests in South Africa: Current status and future prospects.

Invertebrate pests pose a significant threat to food security on the African continent. In response, South Africa has become one of the largest importers of chemical pesticides in sub-Saharan Africa, with several hundred active ingredients registered. To address the over-reliance on such chemicals, the South African Department of Agriculture, Forestry and Fisheries (DAFF) has eliminated or restricted several pesticides since the late 1970s. The recent launch of the South African National Bio-Economy Strategy and establishment of the South African Bioproducts Organisation (SABO), together with new guidelines for registration of biopesticides in 2015, also support this endeavour. Concurrently, entomopathogen-related research and bioproduct development has increased over the past decade. Currently, 31 products (seven manufactured locally) are registered under the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 of 1947. Commercially important microbes include Beauveria bassiana (Cordycipitaceae), Metarhizium anisopliae (Clavicipitaceae), Cydia pomonella granulovirus, Cryptophlebia leucotreta granulovirus, Helicoverpa armigera nucleopolyhedrovirus (Baculoviridae) and Bacillus thuringiensis subsp. kurstaki and B. thuringiensis subsp. aizawai (Bacillaceae). Both parasitic and entomopathogenic nematodes (EPNs) show potential for development as bioinsecticides with one commercial EPN product, based on Heterorhabditis bacteriophora (Heterorhabditidae), registered under the Act. Rapid scientific progression, supported by a favourable legislative environment, should facilitate further advances in microbial control of phytophagous invertebrate pests in South Africa.

Stratification of the ant species (Hymenoptera, Formicidae) in the urban broadleaf woodlands of the city of Kiev

Investigations were carried out in June–August 2012 and 2013 in broadleaf forests and planted stands of the northern red oak Quercus rubra in Kiev. The ant visitation rates of 3–6 most abundant plant species within each vegetation layer were analyzed. In all, 16 species of ants were found in the broadleaf forest (Quercus robur + Acer spp. + Carpinus betulus), with the dominance of three species: Formica rufa, Lasius fuliginosus, and L. emarginatus. Eight ant species occurred in Q. rubra stands with the undergrowth of Acer campestre and A. platanoides; the dominant species were Lasius fuliginosus and L. emarginatus. The northern red oak stands with conspecific undergrowth had only four ant species with no dominants among them. Plants with the highest ant visitation rates in the herbage layer of the broadleaf forest were the invasive Impatiens parviflora and the native Aegopodium podagraria. Ants were rare or absent on the remaining herbs: Impatiens noli-tangere, Carex sylvatica, Stellaria holostea, and Galium odoratum. The herbage layer was mostly visited by influents, the dominants being represented only by Lasius emarginatus. Within the shrub layer, ants most frequently visited the undergrowth of the maple Acer platanoides, often harboring colonies of the aphid Periphyllus lyropictus; the highest visitation rates were recorded in the dominants L. emarginatus and L. fuliginosus. The arboreal layer had the highest visitation rate and was most often visited by the dominants Lasius fuliginosus, L. emarginatus, and F. rufa. The common oak Q. robur was the most visited tree in broadleaf forests. In addition to providing ants with food (colonies of the aphids Lachnus roboris and Stomaphis quercus, and also phytophagous insects and other invertebrates), these trees were used for nesting by the dominants L. fuliginosus and L. emarginatus. The presence of aphid colonies was also typical of ripe trees and undergrowth of the maple A. platanoides, the second-visited tree in broadleaf forests. The common hornbeam Carpinus betulus was the least frequently visited, though some ant species, usually L. emarginatus, nested in the trunks and branches of old trees. The vertical distribution of ants in broadleaf forests and red oak stands formed two clusters: the influents occupied the lower (herbage and shrub) vegetation layers, while the subdominants and dominants occupied the upper (shrub and arboreal) ones. The smallest number of ant species (1 or 2) in all the vegetation layers was recorded in the areas with F. rufa; areas with L. fuliginosus had twice as many species; the greatest numbers of ant species were found in the areas with L. emarginatus and in those without dominants. This pattern may result from different territoriality of the dominants: the strongest in F. rufa (defending the whole territory) and the weaker in the other two species (defending only a part of the territory). Plants of all the vegetation layers varied in their attractiveness to ants. As a result, the layers had a mosaic structure in their vertical (between-layer) and horizontal (between different plant species within one layer) arrangement. From 60 to 100% of plants of certain species were visited by ants while plants of other species were not visited at all. The main reason for visiting plants by ants was the presence of aphid colonies.

Northern tamarisk beetle (Diorhabda carinulata) effects on established tamarisk-feeding invertebrate populations along the Las Vegas Wash, Clark County, Nevada

Abstract Biocontrol of tamarisk in the southwestern United States, in the form of species belonging to the genus Diorhabda, has been the subject of much research in the past few years in terms of efficacy and impact to native wildlife. This study documents the northern tamarisk beetle's (Diorhabda carinulata) arrival to the Las Vegas Wash in southern Nevada, and its impact on two other nonnative phytophagous invertebrate species that also feed on tamarisk. Our research indicates a negative correlation between the arrival of the northern tamarisk beetle and a population of tamarisk leafhoppers (Opsius stactogalus). There was no significant influence on a population of the splendid tamarisk weevil (Coniatus splendidulus). The arrival of the northern tamarisk beetle resulted in substantial defoliation of tamarisk whereas the two other species had minimal impacts on tamarisk foliage.

Nestling Development of Jackdaws Corvus monedula in Agricultural Landscape

Abstract A Jackdaw colony of over 200 nests, built in cavities of old willow trees along 3 km of a small road running through meadows next to the river Narew in an agricultural landscape (15 km southwest of Białystok, NE Poland), was studied to determine nest locations and construction, onset of egg laying, incubation period, egg parameters, clutch size and hatching success, nestling growth and mortality, breeding success as well as predation. The onset of laying and clutch size were correlated with ambient temperature and precipitation (p < 0.001). Hatching success was also determined by these environmental factors as well as by the degree of predation (p < 0,001). There was a statistically significant correlation between clutch size and hatching success (p < 0.001) as well as fledging success (p < 0.001). Nestlings hatching first or second grew faster, reached a higher body weight, and had a lower mortality rate than those hatching last or second to last. There was also a statistically significant correlation between nestling survival and clutch size as well as ambient temperature (p < 0.001 each). Nestling mortality caused by predators, i. e. mainly by martens Martes foina and domestic cats Felis domestica, was high in periods of intensive burning of the meadows surrounding the Jackdaw colony. However, mortality rate of the youngest nestlings was almost 100% lower in periods of high predation compared to times of low predatory activity. Several groups of insects constituted a high amount of nestling food, e. g. 60% of all Orthoptera occurring in the meadows next to the breeding colony. In that area the total dry body mass of phytophagous invertebrates amounted to 1.4-2.0 g per m2, of which 0.3 g were fed to the nestlings. The percentage of zoophagous invertebrates delivered to the offspring was high with about 30-35%. From an economical point of view, Jackdaws during the breeding season are advantageous in an agricultural landscape because they reduce pest insects significantly while consuming only an insignificant amount of all seeds applied.

Phenotypic and phylogenetic evidence for the role of food and habitat in the assembly of communities of marine amphipods.

The study of community assembly processes currently involves (a) longstanding questions about the relative importance of environmental filtering vs. niche partitioning in a wide range of ecosystems, and (b) more recent questions about methodology. The rapidly growing field of community phylogenetics has generated debate about the choice between functional traits and phylogenetic relationships for understanding species similarities, and has raised additional questions about the contribution of experimental vs. observational approaches to understanding evolutionary constraints on community assembly. In this study, we use traits, a phylogeny, and field surveys to identify the forces structuring communities of herbivorous marine amphipods and isopods living in adjacent seagrass and macroalgae. In addition, we compare our field results to a recently published mesocosm experiment that tested the effects of both trait and phylogenetic diversity on coexistence using the same species and system. With respect to community assembly processes, we found that environmental filtering was the dominant process in macroalgae habitats, that niche partitioning was the dominant process in seagrass habitats, and that the strength of these assembly mechanisms varied with seasonal fluctuations in environmental conditions and resource availability. These patterns are indicated by both phylogenetic relationships and trait distances, but the type of resources being partitioned in seagrass habitats can only be deciphered using trait data. Species coexisting in seagrass in the field differed not in their feeding niche but in traits related to microhabitat use, providing novel evidence of the relative importance of competition for food vs. habitat in structuring communities of phytophagous invertebrates. With respect to methodology, the results for seagrass habitats conflict with those obtained in mesocosms, where feeding trait diversity did promote coexistence and phylogenetic diversity had no effect. This contrast arises because a greater range of traits (some of which have much stronger phylogenetic signal than feeding traits) contribute to community assembly in the field. This highlights a mismatch between the processes that drive community assembly in the field and the processes we isolated in experimental tests, and illustrates that using phylogeny as a single proxy in both contexts may impede the synthesis of observational and experimental results.

Do alien plants escape from natural enemies of congeneric residents? Yes but not from all

As predicted by the enemy release hypothesis, plants are supposedly less attacked by herbivores in their introduced range than in their native range. However, the nature of the natural enemies, in particular their degree of specificity may also affect the level of enemy escape. It is therefore expected that ectophagous invertebrate species, being generally considered as more generalists than endophagous species, are more prompt to colonise alien plants. In Swiss, Siberian and Russian Far East arboreta, we tested whether alien woody plants are less attacked by native herbivorous insects than native congeneric woody plant species. We also tested the hypothesis that leaf miners and gall makers show stronger preference for native woody plants than external leaf chewers. In all investigated regions, leaf miners and gall makers were more abundant and showed higher species richness on native woody plants than on congeneric alien plants. In contrast, external leaf chewers did not cause more damage to native plants than to alien plants, possibly because leaf chewers are, in general, less species specific than leaf miners and gall makers. These results, obtained over a very large number of plant-enemy systems, generally support the hypothesis that alien plants partly escape from phytophagous invertebrates but also show that different feeding guilds may react differently to the introduction of alien plants.

Using functional traits to quantify the value of plant communities to invertebrate ecosystem service providers in arable landscapes

Summary The loss of farmland biodiversity threatens the sustainability of ecosystem services delivered within agricultural landscapes. The functional trait approach has been successfully used in grassland systems to quantify trade‐offs and synergies between services delivered directly by plant communities. Many of the services delivered by arable landscapes, however, depend on invertebrate consumers, and the application of the trait‐based approach to these systems depends on quantifying functional relationships between trophic levels. Two data sets of plant and invertebrate communities from a range of annual crops and uncropped land habitats were analysed. The community‐weighted means of plant functional traits were calculated for the vegetation samples and used as the explanatory variables in a multivariate analysis of plant species composition across habitats. The constrained axes scores were used in statistical models to explain the variance in associated total invertebrate abundance, phytophagous invertebrates and invertebrate numbers weighted by importance in the diet of farmland bird chicks. The multivariate analysis discriminated between plant communities characterized by ruderal traits (high specific leaf area and early flowering) and those with more competitive traits. More ruderal communities also supported proportionally more invertebrates. The suite of traits included in the analysis explained a greater proportion of the variance in invertebrate abundance between uncropped habitats, as opposed to between annual crops. The overlap between the plant traits that respond to disturbance (functional response traits) and those that affect the abundance of phytophagous invertebrates (functional effect traits) and the diet of farmland birds demonstrates the potential for using common functional metrics to integrate the assessment of an ecosystem service across different habitats particularly on uncropped land where intensity of disturbance is the main environmental driver. Synthesis. The quantification of functional linkages between arable plants and the abundance of their associated invertebrate consumer communities is the first step in extending the trait‐based approach to quantify trade‐offs and synergies between ecosystem services developed in grassland systems to landscapes dominated by arable crops. However, applying the functional approach to in‐crop weed communities and other service providers such as pollinators will require the incorporation of additional response and effect traits.

Enhancing floral diversity to increase the robustness of grassland beetle assemblages to environmental change

AbstractIntensive grassland management has produced floristically species poor swards supporting a limited invertebrate fauna. Low cost seed mixtures can be used to increase floristic diversity and so diversify the food resource of phytophagous invertebrate. We quantify trophic links between plants and phytophagous beetles in grasslands established using three seed mixtures. Using food webs, we model secondary extinctions from the beetle communities caused by the loss of host‐plants. Plant species were eliminated according to three scenarios: (1) drought intolerant first; (2) low nutrient status first; (3) stress tolerant first. Diverse seed mixtures containing grasses, legumes, and nonlegume forbs, were more robust to secondary beetle extinctions. The highest diversity seed mixture increased robustness under scenarios of extreme drought in three out of four tested management regimes. Simple and low cost seed mixtures have the potential to promote landscape scale robustness to future environmental change for native invertebrates.

Water stress and harmful insects in agri-forest ecosystems

Present knowledge on ecological services supplied by insects to natural terrestrial ecosystems, allow us to identify many homeostatic mechanisms regulating biological balance as well as life perpetuation of the said ecosystems; at the same time, that knowledge represents a sound referring point to understanding how those mechanisms do work so as to manage them in the anthropized ecosystems (i.e., agriculture and forests), and especially in order to identify in the latter the natural meaning of the so called insect outbreaks, so as to forecast and possibly prevent them; as well as, when needed, to conceive and formulate efficient control strategies having minimal environmental impact. Water factor is crucial with genesis, configuration and conservation of a terrestrial ecosystem (both natural or anthropized) as a whole or in its individual components, but especially concerning plant life as well as plant interactions with phytophagous invertebrates, mainly insects. Insect-plant trophic interactions are principally influenced by the water conditions in the ecosystem, and the impact of phytophagous insects on crops is markedly affected. Extremely severe water stress, especially if prolonged, prevent insect life just like plant’s life but a moderate and not so prolonged water stress, while depressing plant vigour, paradoxically can improve development and multiplication of phytophagous arthropods, with severe consequences on woody plants especially, and forest trees markedly.

Responses of invertebrate trophic level, feeding guild and body size to the management of improved grassland field margins

Summary1. Management of lowland mesotrophic grasslands in north‐west Europe often makes use of inorganic fertilizers, high stocking densities and silage‐based forage systems to maximize productivity. The impact of these practices has resulted in a simplification of the plant community combined with wide‐scale declines in the species richness of grassland invertebrates. We aim to identify how field margin management can be used to promote invertebrate diversity across a suite of functionally diverse taxa (beetles, planthoppers, true bugs, butterflies, bumblebees and spiders).2. Using an information theoretic approach we identify the impacts of management (cattle grazing, cutting and inorganic fertilizer) and plant community composition (forb species richness, grass species richness and sward architecture) on invertebrate species richness and body size. As many of these management practices are common to grassland systems throughout the world, understanding invertebrate responses to them is important for the maintenance of biodiversity.3. Sward architecture was identified as the primary factor promoting increased species richness of both predatory and phytophagous trophic levels, as well as being positively correlated with mean body size. In all cases phytophagous invertebrate species richness was positively correlated with measures of plant species richness.4. The direct effects of management practices appear to be comparatively weak, suggesting that their impacts are indirect and mediated though the continuous measures of plant community structure, such as sward architecture or plant species richness.5. Synthesis and applications. By partitioning field margins from the remainder of the field, economically viable intensive grassland management can be combined with extensive management aimed at promoting native biodiversity. The absence of inorganic fertilizer, combined with a reduction in the intensity of both cutting and grazing regimes, promotes floral species richness and sward architectural complexity. By increasing sward architecture the total biomass of invertebrates also increased (byc.60% across the range of sward architectural measures seen in this study), increasing food available for higher trophic levels, such as birds and mammals.

Effectiveness of spring spraying targeting diapause egg production for controlling redlegged earth mites and other pests in pasture

Earth mites are a complex of related species introduced into Australia in the early part of last century that cause economic damage to crops, especially canola, and to pastures. A general method of chemical control aimed at interrupting the life cycle at the most effective stage, by spraying in the spring before the mites enter diapause, has recently been adopted for controlling earth mites, particularly the redlegged earth mite Halotydeus destructor (Tucker). Here we use paired-paddock treatments and field enclosures to test the effectiveness of this method on pest populations of H. destructor as well as on other pests over two seasons at multiple pasture sites in Victoria. Halotydeus destructor numbers at the start of the winter growing season were suppressed by up to 85%, but this control level was not sustained. The numbers of H. destructor and other pests were similar to or higher than those in the unsprayed areas by spring. Spring spraying is, therefore, a useful means of suppressing H. destructor in early autumn, but its effects disappear relatively quickly over time in Victoria. This strategy also has little impact on the control of the blue oat mite Penthaleus major (Duges) and other phytophagous invertebrate pests.

The importance of sward architectural complexity in structuring predatory and phytophagous invertebrate assemblages

Abstract 1. Although the importance of plant community assemblages in structuring invertebrate assemblages is well known, the role that architectural complexity plays is less well understood. In particular, direct empirical data for a range of invertebrate taxa showing how functional groups respond to plant architecture is largely absent from the literature.2. The significance of sward architectural complexity in determining the species richness of predatory and phytophagous functional groups of spiders, beetles, and true bugs, sampled from 135 field margin plots over 2 years was tested. The present study compares the relative importance of sward architectural complexity to that of plant community assemblage.3. Sward architectural complexity was found to be a determinant of species richness for all phytophagous and predatory functional groups. When individual species responses were investigated, 62.5% of the spider and beetle species, and 50.0% of the true bugs responded to sward architectural complexity.4. Interactions between sward architectural complexity and plant community assemblage indicate that the number of invertebrate species supported by the plant community alone could be increased by modification of sward architecture. Management practices could therefore play a key role in diversifying the architectural structure of existing floral assemblages for the benefit of invertebrate assemblages.5. The contrasting effects of sward architecture on invertebrate functional groups characterised by either direct (phytophagous species) or indirect (predatory species) dependence on plant communities is discussed. It is suggested that for phytophagous taxa, plant community assemblage alone is likely to be insufficient to ensure successful species colonisation or persistence without appropriate development of sward architecture.

Effects and applications of arthropod steroid hormones (ecdysteroids) in mammals

Zooecdysteroids (arthropod steroid hormones) regulate the development of arthropods and probably many other invertebrates. Phytoecdysteroids are analogues occurring in a wide range of plant species, where they contribute to the deterrence of phytophagous invertebrates. The purpose of this short review is to summarise findings on the occurrence, metabolism and pharmacological effects of ecdysteroids in mammalian systems and to draw attention to their potential applications, particularly in gene-switch technology, where ecdysteroid analogues (steroidal and non-steroidal) can be used as effective and potent elicitors.

A new type of effect of potentially hazardous substances: uncouplers of pelagial-benthal coupling.

Hydrobionts are mediators of “biogenic migrationof atoms in the biosphere” [1]. This migration is partlyimplemented in the framework of pelagial–benthalcoupling. Trophic activity of bottom filter feedersresults in consumption of the organic matter of plank-ton synthesized in pelagic zones (see, e.g., [2]). Eventhe organic matter that is not assimilated by fulter feed-ers is involved in pelagial–benthal coupling. Suspendedmatter of aquatic ecosystems (including pellets ofinvertebrates) is subjected to gravitational sedimenta-tion [2, 3]. The pellets of invertebrates are formed as aresult of excretion of unassimilated and undigestedfood of phytophagous invertebrates. The degree of foodassimilation in different taxa of invertebrates rangesfrom 1 to 98% [4, 5]. The mean percentage of foodassimilability averaged over many groups of organismsis 16.2–89.6% (Table 1). Therefore, the rest of the foodmatter (10.4–83.8%) remains unassimilated and settlesto the bottom with pellets. Thus, pellets of invertebratesare able to transport a fraction of organic matter synthe-sized in the pelagic zone by photosynthetic organismsfrom this zone to the bottom layers of aquatic ecosys-tems, i.e., to the habitat of benthic organisms (thebenthal).The goal of this work was to determine whetherthere is a potential hazard of disturbance of the pela-gial–benthal coupling induced by water pollution. Itshould be noted that such a hazard of the pollution-induced disturbance of ecosystems has been almostentirely ignored thus far.Bivalve mollusks were objects of this study.Because bivalve mollusks are involved in eliminationand sedimentation of particles suspended in bulk water,these organisms are components of the pelagial–benthal coupling [6–11].The effect of potassium bichromate, a xenobiotic,on the rate of elimination of suspended particles by theBlack Sea mussel Mytilus galloprovincialis was stud-ied. Experimental methods were described elsewhere[10, 11]. Mussels (kindly provided by of A.V. Pirkovaand A.Ya. Stolbov) were grown in water headers in theoutskirts of the city of Sevastopol. The mean bodyweights (raw weights with shell) of experimental(treated with potassium bichromate) and control mol-lusks were 6.53 and 6.59 g, respectively. Both controland experimental tanks contained 13 specimens ofmussel each. Each tank contained 500 ml of sea water(18ppt). The initial concentration of the yeast Saccha-romyces cerevisiae (SAF-Moment, S.I. Lesaffre, 59703Marcq-France) suspension in tanks was 40 mg dryweight per liter. The water temperature was 23.4 ° C.The optical density was measured spectrophotometrri-cally using a SF-26 LOMO spectrophotometer andcuvettes with an optical path length of 10 mm. Similarexperiments were performed with the oyster Crassos-trea gigas , which was also grown under maricultureconditions.The results of our experiments showed that potas-sium bichromate is capable of inhibiting the filtrationactivity of mollusks (Table 2). This reduces the amountof food available for the digestive system of the mol-lusks. The decrease in the amount of food removedfrom water (i.e., the ration decrease) was accompaniedby a visually observed decrease in the rate of formationof pellets. The amount of pellets in the end of the exper-iment in tanks containing potassium bichromate solu-tion in water (0.05 mg/l) was significantly less than incontrol tanks. It was found in our experiments that oys-ters ( C. gigas ) were significantly less sensitive to potas-sium bichromate than mussels ( M. galloprovincialis ).A similar decrease in the amount of suspended par-ticles (plankton cells) eliminated from water wasobserved in our experiments with other xenobiotics,including surfactants, synthetic washing mixtures(SWMs), and liquid washing mixtures (LWMs) (Table 3).In all cases studied, we found that inhibitors of filtra-tion activity caused a decrease in the rate of formationof pellets. Only a few examples of such effects areshown in Table 3. Inhibition of filtration processes wasalso reported by J. Widdows, P. Donkin, D. Page,A.V. Mitin, and some other researchers [9, 10].In addition to experimental studies on planktonelimination from water by marine and freshwater