bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stoichiometry of nutrient excretion by fish: interspecific variation in a hypereutrophic lake
Authors: Torres Lisette E. , Vanni Michael J. 
Published: December 2007

This study investigates how nutrient cycling rates and ratios vary among fish species, with a particular focus on comparing an ecologically dominant detritivore (gizzard shad) to other fishes in a productive lake. We also examined how nutrient cycling rates are mediated by body size (as predicted by allometry theory), and how variation in nutrient cycling is related to body and food nutrient contents (according to predictions of ecological stoichiometry). As predicted by allometry, per capita nitrogen and phosphorus excretion rates increased and mass‐specific excretion rates decreased, with increasing mass. Body phosphorus content was correlated with body mass only in one species, bluegill. Contrary to stoichiometric predictions, there was no relationship between body P and mass‐normalized P excretion rate, or between body N:P and excreted N:P, when all individuals of all species were considered.However, at the species level, we observed some support for a body nutrient content effect on excretion as predicted by stoichiometry theory. For example, gizzard shad had lower body P (high body N:P) and also excreted P at higher rates (lower N:P) than bluegill, which had high body P (lower body N:P). We applied the Sterner (1990) homeostatic stoichiometry model to the two most common species in the study – gizzard shad and bluegill and found that food N:P had a greater effect than consumer body N:P on excreted N:P. This indicates that, in terms of variation among these species, nutrient excretion may be more of a function of food nutrient content than the nutrient content of the consumer. These results suggest that stoichiometry can provide a framework for variation among species in nutrient cycling and for evaluating the ecosystem consequences of biodiversity loss.
Architectural and growth traits differ in effects on performance of clonal plants: an analysis using a field‐parameterized simulation model
Authors: Wildová Radka , Gough Laura , Herben Tomáš , Hershock Chad , Goldberg Deborah E. 
Published: December 2007

Individual traits are often assumed to be linked in a straightforward manner to plant performance and processes such as population growth, competition and community dynamics. However, because no trait functions in isolation in an organism, the effect of any one trait is likely to be at least somewhat contingent on other trait values. Thus, to the extent that the suite of trait values differs among species, the magnitude and even direction of correlation between values of any particular trait and performance is likely to differ among species. Working with a group of clonal plant species, we assessed the degree of this contingency and therefore the extent to which the assumption of simple and general linkages between traits and performance is valid. To do this, we parameterized a highly calibrated, spatially explicit, individual‐based model of clonal plant population dynamics and then manipulated one trait at a time in the context of realistic values of other traits for each species. The model includes traits describing growth, resource allocation, response to competition, as well as architectural traits that determine spatial spread. The model was parameterized from a short‐term (3 month) experiment and then validated with a separate, longer term (two year) experiment for six clonal wetland sedges, Carex lasiocarpa, Carex sterilis, Carex stricta, Cladium mariscoides, Scirpus acutus and Scirpus americanus. These plants all co‐occur in fens in southeastern Michigan and represent a spectrum of clonal growth forms from strong clumpers to runners with long rhizomes.Varying growth, allocation and competition traits produced the largest and most uniform responses in population growth among species, while variation in architectural traits produced responses that were smaller and more variable among species. This is likely due to the fact that growth and competition traits directly affect mean ramet size and number of ramets, which are direct components of population biomass. In contrast, architectural and allocation traits determine spatial distribution of biomass; in the long run, this also affects population size, but its net effect is more likely to be mediated by other traits. Such differences in how traits affect plant performance are likely to have implications for interspecific interactions and community structure, as well as on the interpretation and usefulness of single trait optimality models.
Small mammalian herbivore determines vegetation response to patchy nutrient inputs
Authors: Denyer Joanne L. , Hartley S. E. , John E. A. 
Published: December 2007

Nutrient inputs to plant communities are often spatially heterogeneous, for example those deriving from the dung and urine of large grazing animals. The effect of such localised elevation of nutrients on plant growth and composition has been shown to be modified by the grazing of large herbivores. However, there has been little work on interactions between small mammalian herbivores and such patchy nutrient inputs, even though these interactions are potentially of major significance for plant performance and community structure.We examined the effect of simulated cattle urine deposition on the vegetation structure, above‐ground biomass and species composition of chalk grassland within enriched patches. Short‐term exclosures were used to determine whether a small herbivore (rabbit) would preferentially graze the vegetation in enriched patches and what impact this interaction would have on the performance of plants in such patches. Rabbit grazing pressure determined whether nutrient inputs had a negative or positive effect on plant biomass. Nutrients increased plant biomass in the absence of grazing, but when exposed to grazing, plants in nutrient‐rich patches had more biomass consumed by herbivores than neighbouring plants. Further, nutrients increased the relative palatability of a less preferred forage species (Brachypodium pinnatum), contributing to changes in plant community composition. We conclude that a small herbivore can drive plant responses to patchily distributed nutrients.
What are 60 warblers worth? Killing in the name of conservation
Authors: Vucetich John A. , Nelson Michael P. 
Published: December 2007

Ecological research sometimes entails animal suffering and even animal killing. The ethical appropriateness of animal suffering and killing in conservation research may entail considerations that differ from many other kinds of research. This is true, insomuch as conservation research is specifically motivated by an ethical premise: an appreciation for non‐human life. In striking contrast with other academic fields (e.g. medicine), however, the ethical dimension of conservation research is only rarely discussed. When it is discussed, it tends to be characterized by logical errors. These errors are important because they are general (i.e. both common and with far‐reaching implications), and they are easily made by intelligent people; especially those with no formal training in ethics or logic. Failure to recognize these errors could stymie efforts to increase the ethical quality of ecological research conducted in the name of conservation.We take advantage of a recently published dialogue concerning the ethical appropriateness of a specific field experiment that entailed killing black‐throated blue warblers,Dendroica caerulescens. Both sides of this debate exemplify the kinds of errors to which we refer. In this paper we briefly review the arguments presented on each side of this debate, highlight their mistakes, and indicate necessary corrections. We argue that: (1) compliance with animal research regulations, while important, inadequately accommodates the ethical aspects of animal research, and (2) individual ecologists ought to understand themselves what does and does not represent sound and valid arguments for ethical decisions. Finally, we discuss how any ecological researcher might begin to apply our analysis to his or her own research.
Generalist diurnal pollination provides greater fitness in a plant with nocturnal pollination syndrome: assessing the effects of a Silene – Hadena interaction
Authors: Giménez‐Benavides Luis , Dötterl Stefan , Jürgens Andreas , Escudero Adrián , Iriondo José M. 
Published: December 2007

Nursery pollination in Caryophyllaceae species by Hadena and Perizoma moths has been extensively described in the last few decades. Evidence across multiple pairs of species shows that such pollination systems constitute relatively specialized interactions, shifting between parasitism and mutualism depending on the presence of effective co‐pollinators.In this work, we describe a new specific Silene–Hadena interaction, the Silene ciliata–Hadena consparcatoides system. Although S. ciliata presents a typical nocturnal pollination syndrome, diurnal flower visitors have also been recorded, which motivated us to evaluate the costs and benefits of this nursery moth pollination to the plant. We experimentally induced two pollination regimes at non‐overlapping day‐night periods in a natural population of S. ciliata, and compared their effects on plant reproductive success from flower to seedling stages. Flower scent composition of S. ciliata and antennal responses of H. consparcatoides to this scent were recorded to evaluate the specificity of olfactory signals in this interaction system.In accordance with its nocturnal pollination syndrome, S. ciliata emitted a greater amount of flower scent compounds during the night. Some of the predominant scent compounds, such as benzaldehyde, benzyl acetate and methyl salicylate elicited signals in the antennae of H. consparcatoides. Diurnal pollination produced more fruits per flower than nocturnal pollination, but the latter produced higher brood size resulting in similar overall fecundity. However, seeds generated from diurnal pollination were heavier and germinated better. We conclude that despite its nocturnal pollination syndrome, S. ciliata achieved similar reproductive success and higher offspring vigour under the diurnal pollinator regime. Although H. consparcatoides is specialized in S. ciliata, its shortage or absence would not jeopardize the reproductive success of its host plant. On the contrary, the seed predation exerted by this nursery pollinator shifts the interaction towards parasitism.
The complementarity of single‐species and ecosystem‐oriented research in conservation research
Authors: B. Lindenmayer David , Fischer Joern , Felton Adam , Montague‐Drake Rebecca , D. Manning Adrian , Simberloff Dan , Youngentob Kara , Saunders Debbie , Wilson David , M. Felton Annika , Blackmore Caroline , Lowe Arianne , Bond Suzi , Munro Nicki , P. Elliott Carole 
Published: December 2007

There has been much debate about the relative merits of single‐species vs ecosystem‐oriented research for conservation. This debate has become increasingly important in recent times as resource managers and policy makers in some jurisdictions focus on ecosystem‐level problems. We highlight the potential strengths and limitations of both kinds of research, discuss their complementarity and highlight problems that may arise where competition occurs between the two kinds of research.While a combination of approaches is ideal, a scarcity of funding, time, and expertise means it is impossible to study and manage each species, ecological process, or ecological pattern separately. Making decisions about priorities for the kinds of research, priorities for the kinds of conservation management, and associated allocation of scarce funds is a non‐trivial task. We argue for an approach whereby limited resources for conservation research are targeted at projects most likely to close important knowledge gaps, while also promoting ongoing synergies between single‐species and ecosystem‐oriented research.
Temporal and spatial variability in soil food web structure
Authors: Berg Matty P. , Bengtsson Janne 
Published: December 2007

Heterogeneity is a prominent feature of most ecosystems. As a result of environmental heterogeneity the distribution of many soil organisms shows a temporal as well as horizontal and vertical spatial patterning. In spite of this, food webs are usually portrayed as static networks with highly aggregated trophic groups over broader scales of time and space. The variability in food web structure and its consequences have seldom been examined. Using data from a Scots pine forest soil in the Netherlands, we explored (1) the temporal and spatial variability of a detrital food web and its components, (2) the effect of taxonomic resolution on the perception of variability over time and across space, and (3) the importance of organic matter quality as an explanatory factor for variability in food web composition. Compositional variability, expressed using the Bray‐Curtis similarity index, was measured over 2.5 years using a stratified litterbag design with three organic horizons per litterbag set.Variability in community composition and organic matter degradation increased over time in the litter horizon only. Seasonal variation in community composition was larger than variation between samples from the same season in different years. Horizontal spatial variability in community composition and organic matter degradation was relatively low, with no increase in variability with increasing distance between samples. Vertically, communities and organic matter degradation was more different between the non‐adjacent litter and humus horizons than between adjacent layers.These findings imply that soil food webs, at least in temperate forest plantations, are more variable than is currently appreciated in experiments and model studies, and that organic matter turnover might be an important factor explaining variability in community composition. Species composition was more variable than functional group composition, which implies that aggregated food webs will seem less sensitive to local temporal and spatial changes than they in fact are.
Population dynamic consequences of parasitised‐larval competition in stage‐structured host–parasitoid systems
Authors: White Steven M. , Sait Steven M. , Rohani Pejman 
Published: December 2007

Parasitism can influence many aspects of the host's behaviour and physiology, which in turn can have a profound impact on their population and evolutionary ecology. In many host–parasite interactions there is often a time lag between infection and the death of the host, yet little is known, experimentally or theoretically, about the effects that intra‐class competition between parasitised and unparasitised hosts have on the host–parasite population dynamics.In this article we address this gap in our understanding using a stage‐structured mathematical model for a host–parasitoid interaction, which has been parameterised for thePlodia–Venturiaexperimental system.In the case where parasitised larvae do not compete and do not cannibalise unparasitised larvae, our model predicts a wide range of host–parasitoid dynamics, ranging from host–parasitoid generation cycles, to host generation cycles with parasitoid half‐generation cycles, to host–parasitoid equilibria, to host generation cycles with parasitoid extinction.However, when parasitised larvae can compete with their unparasitised larvae counterparts, the host–parasitoid population dynamics can dramatically change. In particular, we show that high levels of competition exerted by unparasitised larvae upon parasitised larvae is more likely to lead to parasitoid extinction.In addition, we demonstrate that unparasitised host larvae that are sufficiently susceptible to intra‐class competition, or parasitised host larvae that are sufficiently strong competitors, can have a stabilising effect on the host–parasitoid population dynamics.The implications of these theoretical results are discussed in light of our understanding of host–parasitoid interactions and host–parasite systems in general.
Above‐ and belowground insect herbivores differentially affect soil nematode communities in species‐rich plant communities
Authors: De Deyn Gerlinde B. , Van Ruijven Jasper , Raaijmakers Ciska E. , De Ruiter Peter C. , Van Der Putten Wim H. 
Published: December 2007

Interactions between above‐ and belowground invertebrate herbivores alter plant diversity, however, little is known on how these effects may influence higher trophic level organisms belowground. Here we explore whether above‐ and belowground invertebrate herbivores which alter plant community diversity and biomass, in turn affect soil nematode communities. We test the hypotheses that insect herbivores 1) alter soil nematode diversity, 2) stimulate bacterial‐feeding and 3) reduce plant‐feeding nematode abundances. In a full factorial outdoor mesocosm experiment we introduced grasshoppers (aboveground herbivores), wireworms (belowground herbivores) and a diverse soil nematode community to species‐rich model plant communities. After two years, insect herbivore effects on nematode diversity and on abundance of herbivorous, bacterivorous, fungivorous and omni‐carnivorous nematodes were evaluated in relation to plant community composition.Wireworms did not affect nematode diversity despite enhanced plant diversity, while grasshoppers, which did not affect plant diversity, reduced nematode diversity. Although grasshoppers and wireworms caused contrasting shifts in plant species dominance, they did not affect abundances of decomposer nematodes at any trophic level. Primary consumer nematodes were, however, strongly promoted by wireworms, while community root biomass was not altered by the insect herbivores. Overall, interaction effects of wireworms and grasshoppers on the soil nematodes were not observed, and we found no support for bottom‐up control of the nematodes. However, our results show that above‐ and belowground insect herbivores may facilitate root‐feeding rather than decomposer nematodes and that this facilitation appears to be driven by shifts in plant species composition. Moreover, the addition of nematodes strongly suppressed shoot biomass of several forb species and reduced grasshopper abundance. Thus, our results suggest that nematode feedback effects on plant community composition, due to plant and herbivore parasitism, may strongly depend on the presence of insect herbivores.
Habitat predicts reproductive superfetation and body shape in the livebearing fish Poeciliopsis turrubarensis
Authors: Jaime Zúñiga‐Vega J. , N. Reznick David , B. Johnson Jerald 
Published: December 2007

Superfetation, the ability of females to simultaneously carry more than one brood at different developmental stages, is an unusual reproductive strategy that has independently evolved several times in the livebearing fish family Poeciliidae. Why this strategy has evolved remains uncertain. One hypothesis is that superfetation is a response to selective pressures that constrain the physical space within a female in which her offspring can develop. This hypothesis is reasonable, because superfetation should reduce the total volume needed to house developing embryos – that is, fewer large, fully developed embryos will be held by a superfetating female (with several broods at different developmental stages) than a non‐superfetating female (where all embryos reach a fully developed stage at the same time).In this study, we explore this ‘morphological constraint’ hypothesis of superfetation by examining the livebearing fish, Poeciliopsis turrubarensis. We found that populations vary markedly in degree of superfetation, with individuals carrying from two to four distinct broods across different geographic areas. These populations also occupy a range of habitat types: some populations occur in slow moving coastal rivers near the ocean, while other populations occur far inland in fast moving waters that drain steep mountain environments. In comparing populations from these two types of environments, we find a strong association between stream habitat type and the degree of superfetation within populations. Fish from inland populations have higher levels of superfetation than their coastal counterparts. In addition, geometric morphometric analysis revealed that inland populations are also more fusiform than fish from coastal locations. Combined, these two lines of evidence support the ‘morphological constraint’ hypothesis, and suggest that the life history strategy of superfetation could be driven by environmental pressures that favor a more streamlined phenotype.
The relative role of dispersal and local interactions for alpine plant community diversity under simulated climate warming
Authors: Klanderud Kari , Totland Ørjan 
Published: December 2007

Most studies on factors determining diversity are conducted in temperate or warm regions, whereas studies in climatically harsh and low productivity areas, such as alpine regions, are rare. We examined the relative roles of seed availability and different biotic and abiotic factors for the diversity of an alpine plant community in southern Norway. Furthermore, because climate warming is predicted to be an important driver of alpine species diversity, we assessed how the relative impacts of dispersal and local interactions on diversity might change under experimental warming (open top chambers, OTCs).Addition of seeds from 27 regional species increased community diversity. The establishment of the species was negatively related both to the diversity of the existing system and the cover of the abundant dwarf shrubDryas octopetala. These results show that both species dispersal limitation and local biotic interactions are important factors for alpine plant community diversity. Despite relatively harsh environmental conditions and low productivity, competition from the resident vegetation appeared to have a greater role for species establishment and diversity than facilitation and experimental warming. Higher temperature appeared to increase the negative relationship between resident species diversity and species establishment. This may suggest that climate warming can increase the role of interspecific competition for alpine plant community structure, and thus alter the long‐term effects of biotic interactions on diversity.
The French Vocational Education and Training System: like an unrecognised prototype?
Authors: BOUDER ANNIE , KIRSCH JEAN‐LOUIS 
Published: December 2007

The genesis of this article is based on the observation by the authors that the French training system has witnessed an evolution since the 1970s that corresponds to the one that was later recommended by the European authorities, i.e.:

the creation of a national qualifications framework that integrates general and vocational training and initial and continuing education;
a description of qualifications in terms of occupational standards that corresponds to learning outcomes and includes the concept of competence.

Hence, the proposal of an article in two parts:

the first describes the construction process of a national qualifications framework in France. It gives the highlights of the debates that accompanied this construct and stresses the closeness one can find with the present discussions at the European level;
basing itself on this, the second part of the article assesses the results of the implementation of this system in relation to the European goals such as the shift from a system that is steered by supply to one that is steered by demand and the better coherence of qualifications and their transparency for the users.