bluuebunny/crossref_metadata_2025_split huggingface dataset:
Additive partitioning of aquatic invertebrate species diversity across multiple spatial scales
Authors: STENDERA SONJA E. S. , JOHNSON RICHARD K. 
Published: July 2005

Summary1. Additive partitioning of three measures of diversity (species richness, Shannon's diversity index H and Simpson's diversity D) was used to study the relationship between local and regional diversity of benthic macroinvertebrate communities of boreal lakes (littoral habitats) and streams (riffle habitats) across three spatial scales (sampling sites, ecoregions and biogeographic regions).2. Alpha (α) and beta (β) diversity are defined as within‐habitat and between‐habitat diversity, respectively. According to the concept of additive partitioning, diversity can be partitioned across multiple spatial scales such that the total (γ) diversity on one spatial scale becomes within‐habitat (α) diversity at the next higher scale. Hence, the total diversity at one scale is determined by the α diversity and the between‐habitat diversity (β) at the next lower scale. Consequently, one of the advantages of additive partitioning is that it is possible to study simultaneously β diversity and the regional‐local species relationship and the scale dependence of α and β components.3. For both lakes and streams α diversity was low for sites and ecoregions, whereas β diversity was high, indicating that among‐site factors are important in describing the variability among the lakes and streams studied here.4. Weak, albeit significant, evidence was found for regional and local species saturation patterns. Multiple stepwise regression indicated that local processes might be more important in structuring lake‐littoral and stream‐riffle species assemblages than regional processes. From these results we conclude that environmental heterogeneity may act as an important factor contributing to species coexistence, resulting in the observed saturation patterns.5. Our study supports the use of additive partitioning for identifying specific patterns of macroinvertebrate diversity on multiple spatial scales and the underlying processes generating these patterns. This information is needed to improve understanding of the relation between patterns and processes affecting (decreasing) trends in aquatic biodiversity.
Water temperature determines strength of top‐down control in a stream food web
Authors: KISHI DAISUKE , MURAKAMI MASASHI , NAKANO SHIGERU , MAEKAWA KOJI 
Published: July 2005

Summary1. We examined effects of water temperature on the community structure of a three trophic level food chain (predatory fish, herbivorous caddisfly larvae and periphyton) in boreal streams. We used laboratory experiments to examine (i) the effects of water temperature on feeding activities of fish and caddisfly larvae and on periphyton productivity, to evaluate the thermal effects on each trophic level (species‐level experiment), and (ii) the effects of water temperature on predation pressure of fish on abundance of the lower trophic levels, to evaluate how temperature affects top‐down control by fish (community‐level experiment).2. In the species‐level experiment, feeding activity of fish was high at 12 °C, which coincides with the mean summer temperature in forested streams of Hokkaido, Japan, but was depressed at 3 °C, which coincides with the mean winter temperature, and also above 18 °C, which coincides with the near maximum summer temperatures. Periphyton productivity increased over the range of water temperatures.3. In the community‐level experiments, a top‐down effect of fish on the abundance of caddisfly larvae and periphyton was clear at 12 °C. This effect was not observed at 3 and 21 °C because of low predation pressure of fish at these temperatures.4. These experiments revealed that trophic cascading effects may vary with temperature even in the presence of abundant predators. Physiological depression of predators because of thermal stress can alter top‐down control and lead to changes in community structure.5. We suggest that thermal habitat alteration can change food web structure via combinations of direct and indirect trophic interactions.
The use of indicator taxa as representatives of communities in bioassessment
Authors: NIJBOER R. C. , VERDONSCHOT P. F. M. , VAN DER WERF D. C. 
Published: July 2005

Summary1. Sampling and processing of benthic macroinvertebrate samples is time consuming and expensive. Although a number of cost‐cutting options exist, a frequently asked question is how representative a subset of data is of the whole community, in particular in areas where habitat diversity is high (like Dutch surface water habitats).2. Weighted averaging was used to reassign 650 samples to a typology of 40 community types, testing the representativeness of different subsets of data: (i) four different types of data (presence/absence, raw, 2log‐ and ln‐transformed abundance), (ii) three subsets of ‘indicator’ taxa (taxa with indicator weights 4–12, 7–12, and 10–12) and (iii) single taxonomic groups (n = 14) by determining the classification error.3. 2log‐ and ln‐transformed abundances resulted in the lowest classification error, whilst the use of qualitative data resulted in a reduction of 10% of the samples assigned to their original community type compared to the use of ln‐transformed abundance data.4. Samples from community types with a high number of unique indicator taxa had the lowest classification error, and classification error increased as similarity among community types increased. Using a subset of indicator taxa resulted in a maximum increase of the classification error of 15% when only taxa with an indicator weight 10–12 were included (error = 49.1%).5. Use of single taxonomic groups resulted in high classification error, the lowest classification error was found using Trichoptera (68%), and was related to the frequency of the taxonomic group among samples and the indicator weights of the taxa.6. Our findings that the use of qualitative data, subsets of indicator taxa or single taxonomic groups resulted in high classification error implies low taxonomic redundancy, and supports the use of all taxa in characterising a macroinvertebrate community, in particular in areas where habitat diversity is high.
Ecological interactions between Nile tilapia (Oreochromis niloticus, L.) and the phytoplanktonic community of the Furnas Reservoir (Brazil)
Authors: FIGUEREDO CLEBER C. , GIANI ALESSANDRA 
Published: July 2005

Summary1. Exotic invasive species modify natural food webs in a way frequently hard to predict. In several aquatic environments in Brazil the introduction of Oreochromis niloticus (tilapia) was followed by changes in water quality. Yet, because of its rapid and easy growth, this fish has been used in many aquaculture programmes around the country.2. To measure the effects of tilapia on the phytoplankton community and on water conditions of a large tropical reservoir in south‐eastern Brazil (Furnas Reservoir), we performed two in situ experiments using three controls (no fish) and three tilapia enclosures (high fish density). Abiotic and biotic parameters were measured at 4 day intervals for 28 days.3. Fish presence increased nitrogen (N) and phosphorus (P) availability (ammonium 260 and 70% mean increase – first and second experiment; and total phosphorus 540 and 270% mean increase) via excretion. Nutrient recycling by fish can thus be significant in the nutrient dynamics of the reservoir. The higher chlorophyll a concentration in the experimental fish tanks (86 and 34 μg L−1, first and second experiment, respectively) was the result of a positive bottom‐up effect on the phytoplankton community (approximately 2 μg L−1 in the reservoir and control tank).4. Because tilapia feed selectively on large algae (mainly cyanobacteria and diatoms), several small‐sized or mucilaginous colonial chlorophyceans proliferated at the end of the experiments. Thus, the trophic cascade revealed strong influences on algal composition as well as on biomass.5. Tilapia can contribute to the eutrophication of a waterbody by both top‐down and bottom‐up forces. In particular, by supplying considerable amount of nutrients it promotes the increase of fast growing algae. Tilapia must be used cautiously in aquaculture to avoid unexpected environmental degradation.
Strong impact of wintering waterbirds on zebra mussel (Dreissena polymorpha) populations at Lake Constance, Germany
Authors: WERNER STEFAN , MÖRTL MARTIN , BAUER HANS‐GÜNTHER , ROTHHAUPT KARL‐OTTO 
Published: July 2005

Summary1. Since zebra mussel invaded Lake Constance in the 1960s the number of wintering waterbirds increased fourfold. We studied the impact of predation by waterbirds (tufted duckAythya fuligula, pochardAythya ferinaand cootFulica atra) on the population ofDreissena polymorphain winter 2001/2002. These three species, with monthly peak numbers of approximately 230 000 individuals, currently comprise up to 80% of the waterbird population wintering at Lake Constance.2. Four different study sites and four depths, that represent typical and characteristic habitats of mussels in Upper Lake Constance, were chosen.3. Zebra mussels were sampled before, during and after predation by waterbirds. Their biomass in shallow areas decreased by >90%; the biomass reduction in deeper areas was highly variable and dependent on the substratum. With one exception, no changes could be detected at the greatest depth (11 m).4. Concurrent exclosure studies revealed that the decrease in zebra mussels was caused by waterbird predation. A GIS‐based approximation revealed that in an area of 1 km2a total of approximately 750 t mussel fresh mass was removed by birds, which is equivalent to 1390 g mussels per bird per day.5. Wintering waterbirds have a strong structural impact on the littoral community of Lake Constance and could be the key predator of zebra mussels.
Nitrogen absorption by roots as a cause of interspecific variations in leaf nitrogen concentration and photosynthetic capacity
Authors: OSONE Y. , TATENO M. 
Published: July 2005

Summary

Optimal biomass allocation models predicted that an increase in specific absorption rate (SAR: nitrogen absorption rate per unit root dry weight) increases the optimal leaf N concentration (LNC) which maximizes whole‐plant growth rates. From this prediction, we hypothesized that inherent differences in the N absorption ability of roots, which is represented by differences in SAR, causes interspecific differences in LNC and photosynthetic capacity (Pmax).
Four deciduous tree species and three herb species were grown under controlled conditions to test this hypothesis. Despite growing under the same soil N conditions, the SAR of these species differed more than sixfold, with the deciduous trees having a smaller SAR than the herbs. Consistent with the hypothesis, there were strong positive correlations between SAR, LNC and Pmax. Leaf dry mass per area and the LNC–Pmax relationship, factors correlated with leaf life span, differed little among the species, suggesting a small effect of differences in these properties on the variation in LNC.
Simulations were performed using an optimal biomass allocation model and parameter values determined from measurements of each species. These demonstrated that the observed variation in LNC could be explained largely by differences in the N absorption ability of the species.
Additionally, the causal relationship between N absorption ability and LNC, suggested by optimal biomass allocation models, was verified by manipulating the biomass allocation between roots and leaves of Morus bombycis using uniconazole, an inhibitor of gibberellin synthesis.
These results indicate a close functional link between N absorption ability and LNC, which would account for large variations in LNC and Pmax across species.
CO2and nitrogen, but not population density, alter the size and C/N ratio ofPhytolacca americanaseeds
Authors: HE J.‐S. , FLYNN D. F. B. , WOLFE‐BELLIN K. , FANG J. , BAZZAZ F. A. 
Published: July 2005

SummaryPlants can provision seeds by optimizing seed size, number and nutrient content to maximize parental fitness. According to the McGinley–Charnov hypothesis, seed size should be determined by the ratio of carbon to nitrogen (C/N) available to the plant, with larger seed size correlating with larger C/N ratios and smaller absolute N content.This hypothesis was tested by establishing monocultures ofPhytolacca americanaL. (Phytolaccaceae) at three population densities under ambient and elevated CO2environments, with two availabilities of soil N.Elevated CO2reduced both seed size and N concentration while increasing the C/N ratio; high soil N availability produced the opposite result for N concentration and C/N ratio. Higher planting densities reduced plant biomass, but did not alter seed size.In accordance with the McGinley–Charnov hypothesis, larger seeds had both larger C/N ratios and smaller N content. However, the increase in C/N ratio caused by elevated CO2corresponded with smaller seeds overall: elevated CO2reduced seed size, although the seed size–C/N relationship remained positive.These results suggest an alternative mechanism to explain variation in seed size, and suggest that future climate conditions may alter seed quality and plant reproductive behaviour.
Tree growth is related to light interception and wood density in two mixed dipterocarp forests of Malaysia
Authors: KING D. A. , DAVIES S. J. , SUPARDI M. N. NUR , TAN S. 
Published: July 2005

Summary

The development of simple predictors of tree growth is important in understanding forest dynamics. For this purpose, tree height, crown width in two perpendicular directions, trunk diameter at 1·3 m height (d.b.h.) and crown illumination index (CI) were determined for 727 pole‐sized trees (8–20 cm d.b.h.) of 21 species, on forest dynamics plots at Pasoh Forest Reserve, Peninsular Malaysia and Lambir Hills National Park, Sarawak, Malaysia. A light‐interception index (LI = AcrCI2, where Acr is crown area) was calculated for each tree, and wood density (stem wood dry mass/fresh volume) was estimated for each species from reported values.
Diameter growth rates were linearly correlated with LI (mean per species r2 = 0·45, excluding substantially damaged and vine‐covered trees).
Among trees of all species, diameter growth rate was highly correlated with LI/wood density.
Mean growth rate per species varied 10‐fold among the study species, but increased linearly with mean LI/wood density ratio (r2 = 0·78), consistent with the previous pattern.
Thus much of the variability in tree growth rates, both within and among species, can be accounted for by the simple mechanistic assumption that, within a given size class, growth is proportional to light interception/wood density.
Genotype by environment interactions in the nectar production of Echium vulgare
Authors: LEISS K. A. , KLINKHAMER P. G. L. 
Published: July 2005

Summary

Genotype by environment interactions for nectar production in Echium vulgare were studied. Nectar production was measured under high and low‐water treatments for high and low nectar‐producing genetic lines in a growth chamber. In the field the response of nectar production and pollinator behaviour to water availability for potted plants chosen from field populations was studied.
Plants selected from high‐nectar lines produced significantly more nectar than those selected from low‐nectar lines. Nectar production thus had a heritable component.
Under high water conditions plants produced more nectar than under low water conditions. The increase in nectar production under high water availability was strongest for the low‐nectar plants, demonstrating a genotype by environment interaction. Only under dry conditions, which usually prevail during the flowering period of E. vulgare, high and low‐nectar plants differ in nectar production.
Plants selected from high‐nectar lines had a significantly higher root mass and root : shoot ratio. This suggests that they are less affected by low water availability and thus able to maintain high nectar production under dry conditions.
In the field, high‐nectar plants produced significantly more nectar but did not receive more pollinator visits. Watered plants produced significantly more nectar and did receive an enhanced pollinator service. When watered, nectar production and pollinator service was similar for high and low‐nectar plants.
Foliar fibre predicts diet selection by invasive Red Deer Cervus elaphus scoticus in a temperate New Zealand forest
Authors: FORSYTH D. M. , RICHARDSON S. J. , MENCHENTON K. 
Published: July 2005

Summary

There is much interest in how herbivores interact with plant communities, but the association between foliar traits and the feeding behaviour of invading browsing mammals has not been explored in this context.
We investigated whether eight foliar traits predicted the preferences of invasive Red Deer for 21 woody plant species in lowland forest in southern New Zealand.
The four models with substantial support for predicting variation in two indices of diet selection all included one or more traits related to foliar fibre (acid detergent fibre; acid detergent cellulose; acid detergent lignin). In all models the coefficients were negative, indicating that as the concentrations of foliar fibre increased, the preference of deer for foliage decreased.
Our results thus link the feeding behaviour of Red Deer with previously demonstrated shifts in the composition of New Zealand forests towards understorey species and leaf litter with high concentrations of foliar fibre.
Effects of season, understorey vegetation density, habitat edge and tree diameter on patch‐use by bark‐foraging birds
Authors: WHELAN C. J. , MAINA G. G. 
Published: July 2005

Summary

We provided equal feeding opportunities for bark‐foraging bird species across seasons, cleared and uncleared woody understories, edge‐to‐interior habitat and tree diameters in a deciduous oak forest in north‐eastern Illinois, USA, to determine habitat preferences of these bird species. We determined habitat preferences by quantifying patch‐use intensity.
Patch‐use intensity was greater in the breeding season than in the non‐breeding season, and in interior than in edge habitat. In addition, however, we found interactions among the habitat variables. For instance, these bird species showed significant preferences for foraging in woodland interior habitat and on large diameter trees in the breeding season, but not in the non‐breeding season.
Foraging preferences were further affected by understorey clearing, with preference for interior over edge habitat reversed in the cleared habitat in the non‐breeding season. This effect may reflect unintended consequences of topography, an uncontrolled factor outside the experiment protocol.
Overall, the results suggest that patch‐use results from the response of the bird species to effects of vegetation variation from edge to interior habitat on both microclimate and predation risk. Those effects of vegetation may disappear or diminish when understorey vegetation is removed or reduced.
Super size me: an experimental test of the factors affecting lipid content and the ability of residual body mass to predict lipid stores in nestling European Starlings
Authors: ARDIA D. R. 
Published: July 2005

SummaryLipids are a major source of energy storage in vertebrates. A cross‐fostering brood manipulation was conducted to assess the role of rearing environmentvscommon origin on lipid stores.Rearing conditions, especially nest temperatures, explained more variation in lipid levels than did nest of origin. As nest temperatures increased, lipid levels in nestlings also increased. Larger individuals, reflected in both wet and lean dry mass, tended to store more lipids.There was no trade‐off between structural growth and lipid stores. However, body mass growth was linked with lipids. In addition, nestlings raised early in the season tended to maintain greater lipid levels, suggesting a role of individual quality.Because the assessment of lipid stores is difficult, it is common to use residual body mass (RBM) as a surrogate. Multiple methods of calculating RBM were compared with actual lipid mass in nestling European Starlings (Sturnus vulgaris). RBM was correlated with lipid levels (R2up to 0·66); models calculated using ordinary least squares regression predicted lipid stores better than reduced major axis regression.These results indicate that RBM can be a non‐invasive predictor of lipid levels in nestling birds and that studies examining variation in physiological stores should consider development conditions and individual quality.
Digestive plasticity in Mallard ducks modulates dispersal probabilities of aquatic plants and crustaceans
Authors: CHARALAMBIDOU I. , SANTAMARÍA L. , JANSEN C. , NOLET B. A. 
Published: July 2005

Summary

The consequences of plastic responses of the avian digestive tract for the potential of birds to disperse other organisms remain largely uninvestigated.
To explore how a seasonal diet switch in Mallard (Anas platyrhynchos L.) influences their potential to disperse plants and invertebrates, we recorded the retention time of markers, following exposure to two diets of contrasting digestibility (trout chow vs seeds).
We then recorded the retrieval and germination of Fennel Pondweed (Potamogeton pectinatus L.) seeds and Brine Shrimp (Artemia franciscana Kellogg) cysts ingested by the same birds.
Gut passage rates of markers were increasingly longer in birds on the seed‐based, high‐fibre diet and shorter in birds on the animal‐based, low‐fibre one.
Propagule digestibility, and thus survival to gut passage, differed between diet groups, with more seeds and fewer cysts retrieved from ducks on the animal‐based diet. Germination decreased with retention time, but was not affected by diet.
Differences in passage rates of markers but not of seeds and cysts suggest no change in dispersal distances of plants and invertebrates between seasons, while differences in digestibility would affect the numbers of propagules dispersed.
The role of distillation on the quality of tequila
Authors: Rogelio Prado‐Ramírez , Victor Gonzáles‐Alvarez , Carlos Pelayo‐Ortiz , Norberto Casillas , Mirna Estarrón , Héctor E. Gómez‐Hernández 
Published: July 2005

SummaryThe role of a batch rectification on the quality of tequila, a traditional Mexican beverage, was studied. It was shown that the official tequila standard composition, particularly the size of the slop cuts and the correct balance of flavour constituents, can be determined by monitoring the concentration of the regulated compounds (ethanol, methanol, higher alcohols, ethyl acetate, acetaldehyde and furfural) throughout the rectification process. It was found that these regulated compounds are produced over the same time scales when either stainless steel or copper alembics are used. When distillations were done in copper alembics, however, it was found that the copper content of the rectified product exceeded the amount permitted in the official tequila standards. Finally, we report a comparison of sensory properties of tequila distillates obtained in both copper and stainless steel alembics.