Matching consumer feeding behaviours and resource traits: a fourth‐corner problem in food‐web theory

For decades, food web theory has proposed phenomenological models for the underlying structure of ecological networks. Generally, these models rely on latent niche variables that match the feeding behaviour of consumers with their resource traits. In this paper, we used a comprehensive database to evaluate different hypotheses on the best dependency structure of trait‐matching patterns between consumers and resource traits. We found that consumer feeding behaviours had complex interactions with resource traits; however, few dimensions (i.e. latent variables) could reproduce the trait‐matching patterns. We discuss our findings in the light of three food web models designed to reproduce the multidimensionality of food web data; additionally, we discuss how using species traits clarify food webs beyond species pairwise interactions and enable studies to infer ecological generality at larger scales, despite potential taxonomic differences, variations in ecological conditions and differences in species abundance between communities.     

Ricerche sul tessuto parasimpatico dell'ovaio umano

Zusammenfassung Die vom Verf. am menschlichen Material angestellten Forschungen haben den Beweis erbracht, da? mit einer fast konstanten H?ufigkeit im Ovargebiet (Markteil, Hilus, Ligamentum latum) Zellanh?ufungen epithelioidalen Aussehens vorkommen, die eine chromaffine Reaktion aufweisen und in der N?he oder an der Peripherie der sympathischen Nerven oder auch im Innern derselben zwischen den einzelnen Nervenfasern zu liegen kommen. Diese Elemente, meist oval?rer oder polygonaler Form, bergen in sich ein acidophiles, k?rnchenhaltiges oder spugn?ses Protoplasma; der Kern, gew?hnlich klein und exzentrisch gelagert, besitzt eine rundliche Form und ist nur schwer f?rbbar. Das Zellprotoplasma enth?lt oft Fett, Pigmente, manchmal auch Kristalloide. Solche Zellanh?ufungen fehlen wahrscheinlich nie in der Ovargegend des reifen Weibes; nur selten müssen zwecks ihrer Auffindung besondere Serienschnitte angefertigt werden, w?hrend gew?hnlich schon ein entsprechendes Fixierungsverfahren genügt, die Beobachtung oft sehr zahlreicher solcher Gebilde zu erm?glichen. Mit gro?er Wahrscheinlichkeit kann angenommen werden, da? es zwischen diesem im reifen Alter vorzufindenden Gewebe und dem im F?tus und bei Neugeborenen vorhandenen, mit analoger genitaler Lokalisierung, eine gewisse Kontinuit?t gibt. Die vermutliche Homologie der parasympathischen Zellen mit der sogenannten interstitiellen Drüse des Hodens kann nicht ohne weiteres angenommen werden, da ja sonst auch eine sichere bindegewebige Herkunft der parasympathischen Elemente angenommen werden mü?te. Von einem allgemeinen Standpunkt aus ist es nicht ausgeschlossen, da? das parasympathische Ovargewebe auch des innigen topographischen Zusammenhanges wegen, dazu bestimmt sei lokal auf dieselben einzuwirken, sei es vermittels des Adrenalins sei es an Hand eines anderen Inkrets; man kann auch einen Zusammenhang dieses Gewebes und anderer Genitaldrüsen (innensekretorischer) nicht ausschlie?en.

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Con 5 figure nel testo.     

Reciprocal intraguild predation and predator coexistence

Intraguild predation is a mix of competition and predation and occurs when one species feeds on another species that uses similar resources. Theory predicts that intraguild predation hampers coexistence of species involved, but it is common in nature. It has been suggested that increasing habitat complexity and the presence of alternative food may promote coexistence. Reciprocal intraguild predation limits possibilities for coexistence even further. Habitat complexity and the presence of alternative food are believed to promote coexistence. We investigated this using two species of predatory mites, Iphiseiodes zuluagai and Euseius concordis, by assessing co‐occurrence in the field and on arenas differing in spatial structure in the laboratory. The predators co‐occured on the same plants in the field. In the laboratory, adults of the two mites fed on juveniles of the other species, both in the presence and the absence of a shared food source, showing that the two species are involved in reciprocal intraguild predation. Adults of I. zuluagai also attacked adults of E. concordis. This suggests limited possibilities for coexistence of the two species. Indeed, E. concordis invariably went extinct extremely rapidly on arenas without spatial structure with populations consisting of all stages of the two predators and with a shared resource. Coexistence was prolonged on host plant leaves with extra food sources, but E. concordis still went extinct. On small, intact plants, coexistence of the two species was much longer, and ended with the other species, I. zuluagai, often going extinct. These results suggest that spatial structure and the presence of alternative food increase the coexistence period of intraguild predators.     

Orientation of Pea Stem Mitochondrial H+-Pyrophosphatase and Its Different Characteristics from the Tonoplast Counterpart

Proton pumping pyrophosphatase (H⁺-PP_iase) of pea stem mitochondriaappears to be localized on the inner surface of the inner membrane.Aminohexanediphosphonate and dichloromethylenediphosphonateexert different inhibitory effects on this activity and on thatof tonoplast. Antibody raised against membrane-bound mitochondrialH⁺-PP_iase does not react with tonoplast vesicles. Thus, plantmitochondrial H⁺PP_iase seems to have a molecular structure differentfrom that of vacuolar H⁺-PP_iase. (Received August 2, 1996; Accepted October 18, 1996)     

2,3-Dihydro-6,7-dichloro-pyrido[2,3-b]pyrazine-8-oxide as selective glycine antagonist with in vivo activity

2,3-Dihydro-6,7-dichloro-pyrido[2,3-b]pyrazine-8-oxide was synthesized and evaluated for in vitro/in vivo antagonistic activity at the strychnine insensitive glycine binding site on the NMDA receptor revealing it to be a useful tool to evaluate the effectiveness of glycine antagonists in vivo.     

Poly(ADP-ribose) synthesis: a useful parameter for identifying apoptotic cells

Cell death by apoptosis was analysed in HeLa cells either treated with the antitumoral drug bleomycin or depleted of growth factors by long-term culture without medium change. The interference of apoptosis with normal cell cycle progression was followed by flow cytometry in cells stained with propidium iodide and with antibody to S-phase-related PCNA protein. Bleomycin-treated cells showed a net accumulation in G₂/M phase paralleled by the appearance of material with a subdiploid DNA content. Cells with a subdiploid DNA content were also present in growth factor-depleted cultures and were shown to derive from all the cell cycle phases. To identify apoptotic features in HeLa cell cultures, we applied a recently developed assay based on the simultaneous analysis in the single cell of three parameters, namely chromatin condensation, DNA degradation and poly(ADP-ribose) synthesis. Apoptotic cells were visualized by sequential reactions: Hoechst staining, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling assay and immunoreaction with anti-poly(ADP-ribose) monoclonal antibody. Positive reactions were obtained for cells at different stages of the apoptotic programme showing condensed nuclei, fragmented chromatin and apoptotic bodies This revised version was published online in November 2006 with corrections to the Cover Date.     

The dependence of fish community structure and dynamics on floodplain and riparian ecotone zone in Parana River,Brazil

Flood intensity was a main factor determining access to the riparian/floodplain ecotonal resources of the upper Parana River, Brazil, and in consequence determining yield of the dominant trophic groups, which are fish feeding on flooded grasslands and on riparian fruits and leaves. Prey and predator density both declined in years of low floods, and predators did not recover until the next year of high flood, more slowly than in the case prey fish, most probably due to differences in life cycle length. The life cycle of one of the most important species, Curimba (Prochilodus lineatus — Characidae) depends on access to the floodplain lagoons and return to the reservoir after maturation for intensive growth. The riparian/floodplain habitat complexity and connectivity has great significance for fish community dynamics and fisheries yield, and may serve a reason to create a national park in the last floodplain section of the upper Parana River.     

Endosperm-specific demethylation and activation of specific alleles of α-tubulin genes of Zea mays L.

We have investigated the methylation status of the -tubulin genes, and the degree of accumulation of their mRNAs in endosperm, embryo and seedling tissues of Zea mays L. We have found that many of the -tubulin genes are differentially demethylated in the endosperm relative to the embryo and seedling. However, only for tub2 and tub4 could a correlation between DNA demethylation and increased RNA accumulation be detected. By analyzing the inbred lines W64A and A69Y and their reciprocal crosses, we have also identified in the endosperm two -tubulin genes, tub3 and tub4, that are differentially demethylated if transmitted by the maternal germline, but that remain hypermethylated when transmitted by the paternal germline.     

Applications of ecological stoichiometry for sustainable acquisition of ecosystem services

Human activities have differentially altered biogeochemical cycling at local, regional and global scales. We propose that a stoichiometric approach, examining the fluxes of multiple elements and the ratio between them, may be a useful tool for better understanding human effects on ecosystem processes and services. The different scale of impacts of the elements carbon, nitrogen and phosphorus and the different nature of their biogeochemical cycles, imply a large variation of their stoichiometric ratios in space and time and thus divergent impacts on biota.
In this paper, we examine the effects of anthropogenic perturbations on nutrient ratios in ecosystems in two examples and one case study. Altered stoichiometry in agricultural systems (example 1) can affect not only crop yield and quality but also the interactions between plants and their pollinators, pests and pathogens. Human activities have also altered stoichiometry in coastal ecosystems (example 2). Increased N loading has especially lead to increased N:P and reduced Si:N ratios, with detrimental effects on ecosystem services derived from coastal pelagic food webs, such as fish yield and water quality. The terrestrial–aquatic linkage in stoichiometric alterations is illustrated with a case study, the Mississippi River watershed, where anthropogenic activities have caused stoichiometric changes that have propagated through the watershed into the northern Gulf of Mexico.
Coupled with altered stoichiometric nutrient inputs are the inherent differences in variation and sensitivity of different ecosystems to anthropogenic disturbance. Furthermore, the connections among the components of a watershed may result in downstream cascades of disrupted functioning. Applying a multiple element perspective to understanding and addressing societal needs is a new direction for both ecological stoichiometry and sustainability.     

Do domatia mediate mutualistic interactions between coffee plants and predatory mites?

Many plant species possess structures on their leaves that often harbour predatory or fungivorous mites. These so‐called domatia are thought to mediate a mutualistic interaction; the plant gains protection because mites decimate plant pathogenic fungi or herbivores, whereas the mites find shelter in the domatia. We tested this hypothesis using two species of coffee (Coffea spp.) plants that posses domatia consisting of small cavities at the underside of the leaves, and which often harbour mites. We assessed densities of domatia, of the predatory mite Iphiseiodes zuluagai Denmark and Muma (Acari: Phytoseiidae) and of herbivorous mites Oligonychus ilicis (McGregor) (Acari: Tetranychidae) and Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) on Coffea arabica L. (Rubiaceae) and Coffea canephora Pierre in the field. Over a period of 50 days, C. arabica harboured on average 7.5 times more predatory mites and 0.4–0.66 fewer prey mites than C. canephora. Hence, the higher density of predatory mites on C. arabica could not be explained by higher densities of prey. However, the density of domatia on C. arabica was on average 1.65 times higher than on C. canephora, and within each species, leaves with higher densities of domatia also harboured more predators. This suggests a positive effect of domatia on predatory mites. In the laboratory, survival of adult female predatory mites on leaves of C. arabica with open domatia was indeed significantly higher than on leaves with closed domatia. Hence, predatory mites benefited from the domatia. However, plants with higher densities of domatia did not harbour fewer herbivores. Taken together, our study only provides partial evidence for a mutualistic interaction between coffee plants and predatory mites, mediated by domatia.