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Invertebrate immune priming, and other forms of innate immune memory in bacteria, plants, and mammals, modulate the post-infection resistance, tolerance, and survival phenotypes of individuals previously exposed to microbes. By influencing the probability of both transmission and disease-induced mortality, priming is likely to have a significant impact on disease dynamics. Two alternative models have been proposed as frameworks for the role of priming in infected populations, but the differences in their underlying key assumptions yield very different predictions for the effect of priming on disease dynamics. By examining these assumptions from the lens of within-host dynamics, the model presented in this paper demonstrates that priming systems can be characterized along a continuous dose-response gradient that unites these disparate frameworks. Moreover, it facilitates the incorporation of different kinds of immunological plasticity mechanisms, as well as the exposure probability and transmission characteristics of parasites. Simulating the interaction of these thresholds with the diversity of parasite life history strategies and distributions predicts that priming may actually inflate disease prevalence under certain conditions. Thus, priming of innate immune systems may act analogously to leaky vaccines and drive parasite virulence evolution. The results underscore the need for experimental studies that determine dose response curves for the both the probability of becoming primed following primary parasite exposure and shifts in resistance and tolerance in infected primed hosts. This framework is applicable to a variety of systems that show immunological memory. [ABSTRACT FROM AUTHOR]

The present paper deals with caloric values of important plants and insects occurring m the grassland vegetation at Kurukshetra, India. The data indicate variations in energy content among different species and at different seasons. [ABSTRACT FROM AUTHOR]

The article offers an introduction to the research papers featured in the journal including, an analysis of the dynamical behavior of food webs, a detailed study of individual functional responses using individual-level feeding data of terrestrial invertebrates, and another paper on how allometric relationships at the individual level can have great influence on the allometries observed at the community level.

Trophic egg-laying – wherein mothers provide non-developing eggs for offspring to eat – has attracted much empirical attention to diverse taxa (e.g. amphibians, non-social and eusocial insects, fish, and marine gastropods). However, there has been been only a limited exchange of ideas among studies of different taxa. We advocate a unified approach to the study of trophic eggs within an evolutionary ecological framework. In this paper, we stress the importance of elucidating the adaptive function of trophic eggs through explicit hypothesis testing, and our primary objective is to outline key experiments that can test adaptive and functional hypotheses. Currently, some cases of hypothesized trophic eggs may simply represent offspring consumption of eggs that failed to develop for non-adaptive reasons (e.g. sperm limitation). Furthermore, in many trophic egg-laying species, it is unclear whether trophic eggs have evolved to provision offspring or to reduce cannibalism among offspring. With increased focus on theory and hypothesis testing, the study of trophic eggs can offer important insight into topics such as sibling rivalry, parent–offspring conflict, and parental care. [ABSTRACT FROM AUTHOR]

The present paper deals with the species of Oribatei living in a number of northern biotopes. The total number of species found is 127, some of which are new or little known. Most of them are eurytopic but some seem to be strictly bound to one or a few types of environment. In several cases also the eurytopic mites have a tendency to prefer a certain biotope which means that they tend to be strangers in most others. This tendency will be discussed in a following paper. [ABSTRACT FROM AUTHOR]

Biodiversity is known to regulate ecosystem functioning under controlled experimental conditions. However, the 'real‐world' consequences of biodiversity change remain uncertain, as biodiversity–ecosystem function (BEF) relationships observed in nature may be influenced by other drivers. Attempts to disentangle BEF relationships from the effects of confounding factors have so far focused mainly on primary producers, leaving comparatively little known about the impact of changes in consumer diversity despite ecosystems experiencing species extirpations and introductions across trophic levels. Using data from 176 benthic invertebrate assemblages distributed throughout the North Sea, we studied how a fundamental ecological function – secondary production – varies in relation to two components of biodiversity – consumer species richness and evenness – while statistically controlling the effects of abiotic and biotic covariates. Production was enhanced as richness increased or evenness decreased. The relationship with evenness was attributable to its negative covariance with the abundance of small organisms; however, the relationship with richness could not be fully explained by other drivers. Our study reaffirms experimental findings about the functional importance of biodiversity and suggests that losing or gaining consumer species will affect secondary production over a broad range of species richness (20–118 species) in natural ecosystems. [ABSTRACT FROM AUTHOR]

Plasticity in traits in response to environmental conditions can increase fitness, expanding the range of environments within which a genotype can generate viable and productive phenotypes, and therefore when and where populations can persist and diversify in ecological space. Adaptive forms of plasticity in invertebrates are diverse, ranging from polyphenism and diapause to behavioural thermoregulation and optimal foraging. Local patterns of environmental variation and developmental constraints will dictate which of these forms evolves. Here we review the core idea that the use of narrow developmental windows by invertebrates to attain specific types of phenotypic changes reduces their reversibility, while increasing their magnitude. These tradeoffs dictate the costs and effectiveness of plasticity in buffering environmental variation. In particular, plastic responses to narrow developmental or environmental windows increase fitness costs when predicted environmental challenges do not materialise, or when the environment changes in unpredictable ways. We then explore the converse idea that increasing trait reversibility depends on extending the period for which genotypes are sensitive to the environment, but also narrows the range of plastic phenotypes that can be generated. Considering these findings together, we would expect that the costs, benefits and constraints of reversible versus irreversible plasticity affect the rate and magnitude of adaptive responses to rapidly changing and novel environments. However, such predictions have rarely been tested or included in theoretical models. Identifying this knowledge gap leads us to propose new research directions to provide a deeper understanding of the evolution of plasticity in invertebrates and other organisms. We illustrate these possible directions through examples of Drosophila adapting to thermal stress. [ABSTRACT FROM AUTHOR]

Several botanists have investigated the flora of the south bluffs, but only a few zoologists have studied their fauna. The paper presents the results of studies on certain invertebrate groups in some south bluffs in the Swedish provinces of Ångermanland and Lapland. The physiographical conditions of the south bluffs are described and temperature measurements are shown diagrammatically. As expected, the south bluffs facing south were much more favoured than mountains facing north. In spring particularly the temperature differences were very great. There were also obvious differences between the temperatures of a south bluff facing east and of a usual mountain slope facing west. The favourable temperature conditions involved early melting of the snow and insignificant frost. The list of the collected species includes 46 species. Most of them are molluscs. The mollusc material is treated statistically. There is an obvious difference between the south bluffs and other mountains as regards the dominance and constancy of their mollusc faunas; scrubs of different types are intermediate. The differences are smaller between similar habitats in Lapland. Most of the localities investigated had a great mutual affinity on account of the rich occurrence of eurytopic species. In Ångermanland the fauna of the south bluffs was of more southerly character than the fauna of other localities. Yet the dominance of the southern elements was small. There were large similarities, in this respect, between the localities investigated in Lapland and the common deciduous forests in Ångermanland. The importance of the south bluffs for the presence of certain faunal elements in Norrland is evident. Some southern elements seem to have their northernmost occurrences in such localities. A few may be relicts from post-glacial warm period (e. g. Vallonia costata and Ena obscura) while others form northern outposts of wide-spread southern species. The main part of the fauna of the south bluffs consists of very wide-spread Fennoscandian species or northern elements. [ABSTRACT FROM AUTHOR]

Transgenerational effects, whereby the environment experienced by a parent leads to an altered offspring phenotype, have now been described in a variety of taxa. In invertebrates, much of the research on these effects has concentrated on the role of parental exposure to pathogens or immune elicitors in determining offspring immune investment or disease resistance. To date, however, studies of transgenerational effects in invertebrates have generally been restricted to single infections or immune elicitors in ideal laboratory environments. Animals in field situations will commonly experience sub-optimal environments and co-infection by multiple species of parasites and pathogens, leading to increased relative costs of immune investment and changing fitness benefits from offspring responses to the parental environment. Here we investigate a more ecologically realistic scenario involving both multiple infections and resource limitation, using the Indian meal moth Plodia interpunctella as a model host, challenged with the entomopathogenic bacterium Bacillus thuringiensis and fungus Beauveria bassiana. Mothers were exposed to low doses of one or both pathogens, or a control. Offspring from each family were reared on either good- or poor-quality food and then exposed to one or both pathogens. Maternal exposure to pathogens led to reduced pathogen resistance in offspring, depending on the combination of maternal and offspring pathogen-specific infections and resource limitation in the offspring generation. Much research to date has focussed on trans-generational immune priming, in which parental exposure to pathogens or immune elicitors leads to upregulated immune reactivity in their offspring. The lack of any such effects in our system suggests that the production of less resistant offspring following parental exposure to pathogens might be an important alternative, driven by costs of resistance rather than adaptive benefits. [ABSTRACT FROM AUTHOR]

Cross system subsidies of energy and materials can be a substantial fraction of food web fluxes in ecosystems, especially when autochthonous production is strongly limited by light or nutrients. We explored whether assimilation of terrestrial energy varied in specific consumer taxa collected from streams of different sizes and resource availabilities. Since headwater streams are often unproductive, we expected that inputs from surrounding terrestrial systems (i.e. leaf litter, terrestrial invertebrates) would be a more important food source for consumers than in mid-size rivers that have more open canopies and higher amounts of primary production available for consumers. We collected basal resources, invertebrates, and fish along a gradient in stream size in the Adirondack Mountains (NY, USA) and in Trinidad and Tobago and analyzed all samples for hydrogen isotopes as a means of differentiating biomass derived from allochthonous versus autochthonous sources. We found significant differences in allochthonous energy use within individual consumer taxa, showing that some taxa range from being entirely allochthonous to entirely autochthonous depending on where they were collected on the stream size gradient (grazers and collector-gatherer functional feeding groups), while other taxa are relatively fixed in the source of energy they assimilate (shredder and predator functional feeding groups). Consistent with expectations, allochthonous energy use was positively correlated with canopy cover in both regions for most feeding groups, with individuals from small, shaded streams having a more pronounced allochthonous signal than individuals collected from larger streams with less canopy cover. However, consumers in the shredder/detritivore feeding group did not vary among sites in their allochthonous energy use, and had a mostly allochthonous signal regardless of canopy cover and algal biomass. Our results demonstrate that the importance of energy from terrestrial subsidies can vary markedly but are similar in both temperate and tropical streams, suggesting a widely consistent pattern. [ABSTRACT FROM AUTHOR]

In anthropogenic landscapes animals may be lured into low-quality habitats where they survive or reproduce poorly ('ecological traps'). I investigated breeding habitat selection in relation to intra-seasonal changes in food availability and reproductive output in red-necked grebes Podiceps grisegena, a size-limited predator, of common carp Cyprinus carpio ponds. Carp farms constitute highly heterogeneous habitat mosaics due to separate stocking of different age/size fish. Pond features significant for grebe settling decisions, i.e. hydroperiod and emergent vegetation cover, had no obvious effects on prey abundance for chicks and on fledging success. Breeding grebes avoided ponds containing fish too large for them to ingest but exhibited little preference between ponds with medium-sized one-year-old carp that could be exploited by pre-laying birds, and ponds designated for young-of-the-year carp, where only invertebrates and amphibians were available as prey in early spring. Red-necked grebes settling on ponds with medium-sized fish failed to predict future shifts in interactions with carp stocks; carp exceeded the prey-size threshold of chicks and adversely affected their non-fish prey levels. The resulting food shortage led to severe egg-to-fledging mortality rates compared to fishless ponds or those containing young-of-the-year fish. This study shows that waterbirds vulnerable to competition from fish can risk maladaptive habitat selection due to unrecognised spatial and temporal variation in food resources caused by fish stocking practices. Ecological traps created by perturbations to trophic interactions may be common but difficult to detect because altered dynamics of trophic resources can affect wildlife indirectly. As with other types of ecological traps, manipulation of habitat features identified as attractive cues for settling animals, but not related to critical food resources, may help to reduce perceptual pitfalls. For example, wetland management to mitigate trap effects driven by commercially stocked fish should preserve abundant emergent vegetation in habitats with weak fish impact and extend their hydroperiod. [ABSTRACT FROM AUTHOR]

The immune response of a host can have important impacts on host-pathogen interactions, but investment in immunity often changes dynamically across the life history of a host. One form of investment involves the induction of a primed immune response against previously encountered pathogens that protects the host from re-infection. In addition to providing immediate protective effects, immune priming can also provide two types of 'delayed' protection against pathogens: priming across life stages (ontogenic priming) and priming across generations (trans-generational priming). Consequently both types of immune priming have the potential to mediate life history variability in host-pathogen interactions, which could have important consequences for disease prevalence and dynamics as well as for the demographic structure of the host population. Here we develop a stage-structured SIRS model for an invertebrate host to explore the relative and combined impact of ontogenic priming and trans-generational priming on infection prevalence, host population size, and population age structure. Our model predicts that both types of immune priming can dramatically reduce disease prevalence at equilibrium, but their individual and combined effects on population size and age structure depend on the magnitude of tradeoffs between immune protection and reproduction as well as on the symmetry of infection parameters between life stages. This model underscores the potential importance of life-history based immune investment patterns for disease dynamics and highlights the need for wide-spread empirical estimation of parameters that represent the maintenance of immune priming in insects. [ABSTRACT FROM AUTHOR]

Foundation species can provide habitat that modify abiotic and biotic processes that contribute to ecosystem function. While many studies have focused on the processes and consequences of a focal foundation species, understanding the ecological equivalence of co-occurring foundation species is important to identify key species responsible for ecosystem function. Here, we investigated the relative contributions of co-occurring foundation species on abiotic (temperature) and biotic responses of invertebrate species (recruitment, persistence, growth and survival). In a series of experimental field studies, we manipulated foundation species to measure invertebrate recruitment, persistence, and predation. A laboratory experiment measured foundation species effects on herbivore growth. Results demonstrated that macroalgal ( Fucus vesiculosus ecad and Ascophyllum nodosum ecad scorpioides) intermediate foundation species provide habitat, food, and alleviate abiotic stress for dominant littorinid herbivores that surpass that provided by the primary species ( Spartina alterniflora). These foundation effects were species-specific with F. vesiculosus ecad important for early life-history stages (enhanced recruitment and early growth of littorinid snails) and A. nodosum ecad important later on as a refuge from predators ( Carcinus meanas) and stressful temperature. Understanding of the different effects of co-occurring foundation species on population and community processes is necessary for predicting community response to natural disturbance, species invasion, and ecosystem-based management actions. [ABSTRACT FROM AUTHOR]

We studied the relative importance of spatial and environmental factors as determinants of algal, bryophyte, and macroinvertebrate metacommunities in two boreal drainage basins differing in spatial extent. We used eigenfunction spatial analysis to model the spatial relationships among sites and distance-based redundancy analysis to partition the variability in biotic communities between the spatial filters generated through spatial eigenfunction analysis and the environmental factors measured in the field. In the smaller study area, each metacommunity was structured mostly by environmental factors. This was evidenced by the fact that either the pure environmental effect was significant or environmental factors were strongly spatially structured. In the larger study area, only pure environmental effects were significant. These findings suggest that the environmental control prevails in boreal headwater streams. However, our findings also suggest that the specific details of the community-environment and community-space relationships are dependent on the focal organism group and drainage basin. [ABSTRACT FROM AUTHOR]

Recent theoretical advances in food web ecology emphasize the importance of body size disparities among species for the structure, stability and functions of ecosystems. Experimental confirmations of the functional importance of large species, independent of their trophic position, are scarce. We specifically examine the multiple ecological roles of large invertebrates from two distinct trophic levels in headwater streams. We experimentally manipulated the presence of large predatory invertebrates (two Perlid stoneflies) or detritivores (a limnephilid caddisfly and a Pteronarcys stonefly) in a two-by-two design in stream channels open to immigration/emigration of smaller biota. We assessed treatment effects on the trophic structure of the benthic invertebrate community, dynamics of basal resources (benthic algae and leaf litter of cedar and alder), and stability of litter decomposition rates against an experimental pulse perturbation (fine sediment input). The presence of the large invertebrates was associated with a ten-fold decrease in the biomass of invertebrate filterers whereas other trophic groups were unaffected by the large species. The biomass of benthic algae was lower and the rate of mass loss of alder litter was higher in channels lacking the large predators, thus revealing trophic cascades operating along both algal-based and detritus-based food chains. The large predators had no detectable effect on the decomposition of cedar whereas both cedar and alder disappeared faster in the presence of the large detritivores. Furthermore, the large predators and large detritivores interactively influenced the decomposition of the cedar-alder mixture through a litter diversity effect and the variability of the rate of alder decomposition after a pulse of fine sediment. Because the large invertebrates affected multiple ecosystem properties, and as their absence was not rapidly compensated for by small immigrant species, our findings support the notion that large species could be critically important in controlling ecosystem structure and functioning. [ABSTRACT FROM AUTHOR]

Understanding how far the effects of genes extend beyond the phenotype of an individual or population, is fundamental to the developing field of community genetics. We therefore assessed two geographically and genetically distinct populations of the Australian forest tree, Eucalyptus globulus, and the existence of genetic effects on a leaf litter invertebrate community and soil characteristics within a 15 year old common garden. Twenty trees per population were randomly selected for felling and placement of the apical branch next to the stump. This produced a leaf litter habitat of known genotype. Pitfall trap sampling for invertebrates, and linseed bioassay analyses of soil, were conducted within this habitat. Two key findings emerged. Firstly, assessment of 27 invertebrate orders (57 924 individuals) revealed significant population-level variation in leaf litter biodiversity (i.e. in community richness, abundance, composition and beta diversity). Secondly, considerable population-level differences in soil characteristics were evident based on linseed germination and growth responses. While recent findings in E. globulus have demonstrated consequences of genetic variation within forest trees for organisms that interact directly (i.e. proximally) with the living tree, these findings highlight the distal impacts that intraspecific genetic variation may have on communities and ecosystems. Such community genetic considerations have important implications for in situ community conservation, biodiversity management within restoration and plantation forestry, and our understanding of community-level evolutionary interactions involving foundation species. [ABSTRACT FROM AUTHOR]

Habitat complexity is often used to explain the distribution of species in environments, yet the ability to predict outcomes of structural differences between habitats remains elusive. This stems from the difficulty and lack of consistency in measuring and quantifying habitat structure, making comparison between different habitats and systems problematic. For any measure of habitat structure to be useful it needs to be applicable to a range of habitats and have relevance to their associated fauna. We measured three differently-shaped macrophyte analogues with nine indices of habitat structure to determine which would best distinguish between their shape and relate to the abundance and rarefied species richness of their associated macroinvertebrate assemblages. These indices included the physical, whole-plant attributes of surface area (SA) and plant volume (PV), the interstitial space attributes of average space size and frequency (ISI), average refuge space from predation (Sp/Pr), and total refuge space (FFV), and the degree of surface convolution at a range of scales (i.e. the fractal dimension at four spatial scales: 7.5×, 5×, 2.5× and 1× magnification). We found a high degree of inter-correlation between the structural indices such that they could be organised into two suites: one group describing interstitial space and surface convolution at coarse scales, the other describing whole-plant attributes and surface convolution at fine scales. Two of these indices fell into both suites: the average refuge space from predation (Sp/Pr) and the fractal dimension at 5× magnification. These two measures were also strongly related to macroinvertebrate abundance and rarefied species richness, which points to their usefulness in quantifying habitat structure and illustrates that habitat structure depends not just on shape, but on the space associated with shape. [ABSTRACT FROM AUTHOR]

To understand how current patterns of habitat loss and fragmentation will ultimately affect ecosystem functioning, we need to match experimental manipulations of community structure with real changes occurring in the landscapes of today. In this study, we examine the consequences of habitat fragmentation on a key function: the decomposition of dung by invertebrates. In a microcosm experiment, we use previous observations of dung beetle assemblage structure in fragmented and intact landscapes to create realistic differences in assemblages of small, dung-dwelling species in the genus Aphodius. We ask whether such differences will affect ecosystem functioning, and how their effects compare to those of removing full functional groups: dung-dwelling Aphodius, tunnelling Geotrupes stercorarius, and/or earthworms. As measured by changes in dung fresh weight, we observe an overriding impact of removing G. stercorarius, with the amount of dung remaining at any one time doubling if the species is excluded. Compared to this major effect, there seem to be less effects of removing Aphodius, ambiguous effects of excluding earthworms, and no detectable effects of relatively minor changes in Aphodius assemblages as induced by current levels of fragmentation. Overall, our results support the general notion that different species contribute highly unevenly to overall ecosystem functioning. Most importantly though, our findings suggest that the functional consequences of habitat loss will depend on taxon-specific responses to landscape modification. Only by addressing these responses may we predict the actual consequences of habitat loss. [ABSTRACT FROM AUTHOR]

The costs and benefits of activating the immune system can reach across generations. Thus, in vertebrates and in several invertebrates, stimulating the immune system of a female can enhance immunity of her offspring or decrease offspring fitness. We evaluated the potential maternally transmitted costs and benefits of the melanization response, an innate immune response of insects that helps to protect mosquitoes from malaria parasites. We manipulated the maternal melanization response of the yellow fever mosquito Aedes aegypti by inoculating female mosquitoes with negatively charged sephadex beads or with immunologically inert glass beads; a control group was not inoculated. In the next generation, we assayed the melanization response and measured three other life-history traits: survival up to emergence, the age at emergence, and body size (estimated as wing length). We found no evidence of fitness costs or benefits for the offspring. A retrospective power analysis found that our experiment would have detected an effect size that is three times smaller than the maternal immune priming effects that have been reported in the literature. We did find a strong correlation between offspring wing length and melanization response. Overall, our findings indicate that trans-generational immune priming in invertebrates cannot be generalized, and that it may depend on the species, the immune challenge, and the environmental conditions. [ABSTRACT FROM AUTHOR]

The importance to food-webs of trophic cul-de-sacs, species that channel energy flow away from higher trophic levels, is seldom considered outside of the pelagic systems in which they were first identified. On intertidal mudflats, inputs of detritus from saltmarshes, macroalgae or microphytobenthos are generally regarded as a major structuring force underpinning food-webs and there has been no consideration of trophic cul-de-sacs to date. A fully orthogonal three-factor experiment manipulating the density of the abundant gastropod, Pyrazus ebeninus, detritus and macrobenthic predators on a Sydney mudflat revealed large deleterious effects of the gastropod, irrespective of detrital loading or the presence of predators. Two months after experimental manipulation, the standing-stock of microphytobenthos in plots with high (44 per m2) densities of P. ebeninus was 20% less than in plots with low (4 per m2) densities. Increasing densities of P. ebeninus from low to high halved the abundance of macroinvertebrates and the average number of species. In contrast, the addition of detritus had differing effects on microphytobenthos (positively affected) and macroinvertebrates (negatively affected). Over the two-months of our experiment, no predatory mortality of P. ebeninus was observed and high densities of P. ebeninus decreased impacts of predators on macroinvertebrate abundances. Given that the dynamics of southeast Australian mudflats are driven more by disturbance than seasonality in predators and their interactions with prey, it is likely that Pyrazus would be similarly resistant to predation and have negative effects on benthic assemblages at other times of the year, outside of our study period. Thus, in reducing microphytobenthos and the abundance and species richness of macrofauna, high abundances of the detritivore P. ebeninus may severely limit the flow of energy up the food chain to commercially-important species. This study therefore suggests that trophic cul-de-sacs are not limited to the eutrophied pelagic systems in which they were first identified, but may exist in other systems as well. [ABSTRACT FROM AUTHOR]

With global freshwater biodiversity declining at an even faster rate than in the most disturbed terrestrial ecosystems, understanding the effects of changing environmental conditions on relationships between biodiversity and the variability of community and population processes in aquatic ecosystems is of significant interest. Evidence is accumulating that biodiversity loss results in more variable communities; however, the mechanisms underlying this effect have been the subject of considerable debate. We manipulated species richness and nutrients in outdoor aquatic microcosms composed of naturally occurring assemblages of zooplankton and benthic invertebrates to determine how the relationship between species richness and variability might change under different nutrient conditions. Temporal variability of populations and communities decreased with increasing species richness in low nutrient microcosms. In contrast, we found no relationship between species richness and either population or community variability in nutrient enriched microcosms. Of the different mechanisms we investigated (e.g. overyielding, statistical averaging, insurance effects, and the stabilizing effect of species richness on populations) the only one that was consistent with our results was that increases in species richness led to more stable community abundances through the stabilizing effect of species richness on the component populations. While we cannot conclusively determine the mechanism(s) by which species richness stabilized populations, our results suggest that more complete resource-use in the more species-rich low nutrient communities may have dampened population fluctuations. [ABSTRACT FROM AUTHOR]

We used analytical models and random walk simulations in a one-dimensional habitat to study the scale-dependence of migration rates in stream invertebrates. Our models predict that per capita migration rate is inversely proportional to patch length when patches are large compared to the scale of movements. When patches are small the scale-dependence is weaker and primarily determined by the length of individual movements (steps) relative to patch size. Laboratory experiments using isopods ( Asellus aquaticus L .) and mayfly nymphs ( Baetis sp.) confirmed that the strength of the scale-dependence decreased with increasing step length. For the case when step length distributions follow an exponential probability distribution, which is often the case for stream organisms, we provide a simple model that allows the scale-dependence to be predicted from the mean step length. We fitted this model to published field data on drift densities at different downstream distances from a net that blocks the drift from upstream areas. Agreement between model and data was excellent in most cases. We then used already published data on the length of induced drift movements to predict the scale-dependence that was observed in block experiments performed in the same system. Predicted and observed scale-dependence showed very close agreement. We conclude that our models and published data on drift distances can be used to calculate the expected scale-dependence of per capita emigration rates for a large number of taxa under a wide range of environmental conditions. [ABSTRACT FROM AUTHOR]

Understanding the constraints on community composition at multiple spatial scales is an immense challenge to community and ecosystem ecologists. As community composition is basically the composite result of species’ spatial patterning, studying this spatial patterning across scales may yield clues as to which scales of environmental heterogeneity influence communities. The now widely documented positive interspecific relationship between ‘regional’ range and mean ‘local’ abundance has become a generalisation describing the spatial patterning of species at coarse scales. We address some of the shortcomings of this generalisation, as well as examine the cross-scale spatial patterning (aggregation and density levels) of littoral-benthic invertebrates in very large lakes. Specifically, we (a) determine whether the positive range-abundance relationship can be reinterpreted in terms of the actual spatial structure of species distributions, (b) examine the relationship between aggregation and density across different spatial scales, and (c) determine whether the spatial patterning of species (e.g. low density/aggregated distribution) is constant across scales, that is, whether our interpretation of a species spatial pattern is dependent on the scale at which we choose to observe the system. Spatial aggregation of littoral invertebrates was generally a negative function of mean density across all spatial scales and seasons (autumn and spring). This relationship may underlie positive range-abundance relationships. Species that were uncommon and highly aggregated at coarse spatial scales can be abundant and approach random distributions at finer spatial scales. Also, the change in spatial aggregation of closely related taxa across spatial scales was idiosyncratic. The idiosyncratic cross-scale spatial patterning of species implies that multiple scales of environmental heterogeneity may influence the assembly of littoral communities. Due to the multi-scale, species-specific spatial patterning of invertebrates, littoral zone communities form a complex spatial mosaic, and a ‘spatially explicit’ approach will be required by limnologists in order to link littoral-benthic community patterns with ecosystem processes in large oligotrophic lakes. [ABSTRACT FROM AUTHOR]

Analyzes the need to amend the existing methods of measuring marsh grass growth and specifically in case of Spartina productivity in western Atlantic marshes. Importance of marsh primary productivity to ecological studies; Annual rate of productivity among salt marshes; Importance of grazing by abundant invertebrates in regulating marsh plant production.

Discusses the impact of invertebrate phytophages on plant communities. Relationship between invertebrate impact and productivity; Need for a well-designed exclusion experiments across a wide range of primary productivities; Association between effect size of the exclusion of invertebrate herbivores on herbaceous or grassland plant communities and above-ground plant biomass.

The occurrence and impact of algal grazing by invertebrates is widespread and well known in circumneutral streams but poorly understood in acidified streams, where specialist grazing taxa are absent. We examined the ability of the generalist stonefly, Nemurella pictetii (Plecoptera: Nemouridae), maintained at different densities using in-stream experimental enclosures, to depress the biofilm resources coating substrata in an acid stream. Nymphs were reared on the epilithic biofilm coating cobbles in clear aquaria in Lone Oak at 0, 0.5, 1 and 4 times ambient density and their growth rate compared. The biomass and algal taxonomic composition of the biofilm was also compared among treatments and contrasted with stones from the stream. After 23 d, biofilm resources, evidenced by descriptors such as diatom abundance, chlorophyll, carbohydrate and protein content, had been depressed by the nymphs. The acidobiontic diatom Eunotia exigua was harvested more efficiently than other algal taxa when nymphal densities were high. Growth of N. pictetii nymphs in the experimental channels was density dependent and the decline in growth of the nymphs with increasing density was probably due to food limitation. The ability of N. pictetii , often classed as a shredder of leafy detritus, to affect the biomass and composition of epilithic biofilm suggests that this abundant species is an important consumer of algae in acidified systems, where specialist herbivores are often absent. Grazing can clearly be important in acidified streams. [ABSTRACT FROM AUTHOR]

Larvae of Aphodius rufipes L. live in cow pats. They are ‘bulk feeders’ eating dung rather unselectively. Their ingestion, respiration, and production during instars II and III (there are three instars) were determined in the laboratory at 17°C. The efficiency of assimilation (7.0–10.4%) was low, but ingestion rate was high in comparison with other terrestrial detritus feeders. Daily food intake was 380–530% of dry body weight in instar II and 175–300% during the two first weeks of instar III. Also, the growth rate was high and the total growth was accomplished in about six weeks. It appears that energy for rapid growth, necessitated by the instability of the larval habitat, was obtained through a very high ingestion rate which compensates for the poor assimilation of dung. [ABSTRACT FROM AUTHOR]

Radiocesium concentrations in several groups of plants and arthropods were measured on the small islands and floodplain of a stream bed contaminated with radioactive wastes. Mean cesium concentrations were significantly higher on the islands than on floodplain areas. There were no consistent trends for increasing or decreasing concentration across trophic levels. However, the degree of linear correlation between radiocesium concentrations in different types of plants and arthropods was significant and makes possible a model to predict radiocesium levels in other components of the system. Predictability was highest between the various arthropod groups and lowest among the different plant types. Between two possible producer-herbivore-predator associations (broomsedge-grasshopper-spider, and broomsedge-leafhopper-spider) radiocesium concentrations ratios differed significantly. [ABSTRACT FROM AUTHOR]

Focuses on threats to the littoral ecosystem. Stress put on littoral systems by human exploitation, including industrial developments, garbage dumps and harbors; Reduction of invertebrate population in developed littoral ecosystems due to the increased predation pressure introduced by water birds; Threat posed by parasites that lead to a "zero growth" phenomenon in species it infects.