The discovery of a series of genetic and serological markers associated with disease susceptibility and phenotype in inflammatory bowel disease has led to the prospect of an integrated classification system involving clinical, serological and genetic parameters. The Working Party has reviewed current clinical classification systems in Crohn's disease, ulcerative colitis and indeterminate colitis, and provided recommendations for clinical classification in practice. Progress with respect to integrating serological and genetic markers has been examined in detail, and the implications are discussed. While an integrated system is not proposed for clinical use at present, the introduction of a widely acceptable clinical subclassification is strongly advocated, which would allow detailed correlations among serotype, genotype and clinical phenotype to be examined and confirmed in independent cohorts of patients and, thereby, provide a vital foundation for future work.

/pdf/toward-an-integrated-clinical-molecular-and-serological-4qawah6knq.pdf

Toward an Integrated Clinical, Molecular and Serological Classification of Inflammatory Bowel Disease: Report of a Working Party of the 2005 Montreal World Congress of Gastroenterology

The main drivers of global environmental change (CO2 enrichment, nitrogen deposition, climate, biotic invasions and land use) cause extinctions and alter species distributions, and recent evidence shows that they exert pervasive impacts on various antagonistic and mutualistic interactions among species. In this review, we synthesize data from 688 published studies to show that these drivers often alter competitive interactions among plants and animals, exert multitrophic effects on the decomposer food web, increase intensity of pathogen infection, weaken mutualisms involving plants, and enhance herbivory while having variable effects on predation. A recurrent finding is that there is substantial variability among studies in both the magnitude and direction of effects of any given GEC driver on any given type of biotic interaction. Further, we show that higher order effects among multiple drivers acting simultaneously create challenges in predicting future responses to global environmental change, and that extrapolating these complex impacts across entire networks of species interactions yields unanticipated effects on ecosystems. Finally, we conclude that in order to reliably predict the effects of GEC on community and ecosystem processes, the greatest single challenge will be to determine how biotic and abiotic context alters the direction and magnitude of GEC effects on biotic interactions.

/pdf/global-change-and-species-interactions-in-terrestrial-26w7hzgeca.pdf

Global change and species interactions in terrestrial ecosystems.

In this paper, we tested whether the spatial distribution of a given species in more or less fragmented and disturbed landscapes depends on the species habitat specialization. We studied 891 spatial replicates from the French Breeding Bird Survey (FBBS) monitored at least two years during 2001 �2005, and two independent landscape databases measuring respectively landscape fragmentation and recent landscape disturbance on each FBBS replicate. We used a continuous habitat specialization index for the 105 most common bird species monitored by the FBBS. We further modelled the spatial variation in abundance of each species according to fragmentation and disturbance across FBBS replicates, accounting for habitat differences and spatial trends. We then tested whether more or less specialized species responded to landscape fragmentation and disturbance. We found that the more specialist a species, the more negative its spatial response to landscape fragmentation and disturbance. Although there was a very high variation around these tendencies indicating that there are many other drivers of species distribution, our results suggest that measuring specialization may be helpful in predicting which species are likely to thrive in human degraded landscapes. We also emphasize the need to consider both positive and negative species responses when assessing consequences of habitat change in communities.

Distribution of specialist and generalist species along spatial gradients of habitat disturbance and fragmentation

The usefulness of mixtures (multiline cultivars and cultivar mixtures) for disease management has been well demonstrated for rusts and powdery mildews of small grain crops. Such mixtures are more useful under some epidemiological conditions than under others, and experimental methodology, especially problems of scale, may be crucial in evaluating the potential efficacy of mixtures on disease. There are now examples of mixtures providing both low and high degrees of disease control for a wide range of pathosystems, including crops with large plants, and pathogens that demonstrate low host specificity, or are splash dispersed, soilborne, or insect vectored. Though most analyses of pathogen evolution in mixtures consider static costs of virulence to be the main mechanism countering selection for pathogen complexity, many other potential mechanisms need to be investigated. Agronomic and marketing considerations must be carefully evaluated when implementing mixture approaches to crop management. Practical difficulties associated with mixtures have often been overestimated, however, and mixtures will likely play an increasingly important role as we develop more sustainable agricultural systems.

Use of multiline cultivars and cultivar mixtures for disease management

Aim Wo rldwide, functional homogenization is now considered to be one of the most prominent forms of biotic impoverishment induced by current global changes. Ye t this process has hardly been quantified on a large scale through simple indices, and the connection between landscape disturbance and functional homogenization has hardly been established. Here we test whether changes in land use and landscape fragmentation are associated with functional homogenization of bird communities at a national scale. Location France. Methods We estimated functional homogenization of a community as the average specialization of the species present in that community. We studied the spatial variation of this community specialization index (CSI) using 1028 replicates from the French Breeding Bird Survey along spatial gradients of landscape fragmentation and recent landscape disturbance, measured independently, and accounting for spatial autocorrelation. Results The CSI was very sensitive to both measures of environmental degradation: on average, 23% of the difference in the CSI values between two sample sites was attributed to the difference in fragmentation and the disturbance between sites. This negative correlation between CSI and sources of landscape degradation was consistent over various habitats and biogeographical zones. Main conclusions We demonstrate that the functional homogenization of bird communities is strongly positively correlated to landscape disturbance and fragmentation. We suggest that the CSI is particularly effective for measuring functional homogenization on both local and global scales for any sort of organism and with abundance or presence‐absence data.

Functional biotic homogenization of bird communities in disturbed landscapes

Response of a desert lizard community to habitat degradation: Do ideas about habitat specialists/generalists hold?

Summary

1. With increases in river discharge over time and space, zooplankton generally encounter increased turbulence, turbidity, hydraulic forces, downstream advection and food limitations, all of which should affect species diversity and densities. Of these factors, the role of turbulence on the distribution of zooplankton is least known along longitudinal and lateral dimensions in river networks.



2. We tested the factorial effects of turbulence and grazing level on Ohio River potamoplankton in spring and summer using twelve 1600-L, outdoor mesocosms. Turbulence was calculated using the Froude number for equal depths but with current velocities of 0.064 and 0.32 m s−1. Grazing levels corresponded to a high density treatment (=ambient river densities of rotifers, copepods and cladocerans) and a low density treatment (initially no zooplankton >64 μm). All tanks had the same water residence time, and hydraulic stress was minimized by circular flow patterns.



3. Zooplankton densities and population growth rates were significantly affected by turbulence level and season. In general, rotifer populations grew faster in high turbulence tanks (though Keratella and Brachionus populations flourished in both treatments in summer) and microcrustaceans thrived better in low turbulence environments. The larger, calanoid copepods handled more turbulent conditions much better than cyclopoids or nauplii. Zooplankton had no detectable effects on particulate organic carbon concentrations in either month (values were higher in spring), but rotifers reduced chlorophyll concentrations in both months.



4. The relative importance of turbulence in controlling potamoplankton is probably to vary not only on a longitudinal basis in river networks but also with both the hydrogeomorphic complexity of river reaches and the type and amount of river regulation. Plans for river rehabilitation and management should incorporate non-turbulent habitats in large rivers as a means of enhancing zooplankton populations and providing an important food web component for planktivores.

Impact of turbulence on riverine zooplankton: a mesocosm experiment

To predict possible effects of global climatic change (via changes in ambient water temperatures and suspended sediments) on two exotic bivalves (zebra mussel, Dreissena polymorpha, and quagga mussel, Dreissena bugensis), we evaluated survival and growth at three temperatures (ambient, ambient + 2°C, and ambient + 4°C) and two turbidities (ambient and twice ambient) in outdoor tanks for approximately 3 months during both warm and cool seasons. We compared responses of zebra and quagga mussels from southwestern Lake Erie and zebra mussel from the Ohio River at Louisville, Kentucky. Experimental increases in temperature significantly enhanced growth rates in fall - early winter but not during summer - early fall. Elevated temperatures increased mortality in the warm season but not in the cool season. Zebra mussel survived better (especially the Ohio River population) than did quagga mussel at high temperatures. Inorganic turbidity had few detectable effects; relationships, where significant, varied with tem...

Responses of Ohio River and Lake Erie dreissenid molluscs to changes in temperature and turbidity

The use of landmarks to define territorial boundaries.

Disease seventy and crop yield were compared in monocultures and mixtures of two wheat cultivars. one susceptible and one resistant to Puccinia graminis f. sp. tritici. Part of each plot was inoculated and part treated with fungicide. Rust seventy was inversely related to the proportion of resistant plants present. Weight of grain in 100 heads of the susceptible cultivar increased as the amount of rust decreased. The susceptible cultivar yielded less than the resistant cultivar in monoculture, but was a stronger competitor in mixtures. Competitive abilities of the cultivars were independent of severity of rust in the mixtures studied.

Gary A. Cobbs

Papers

Response of a desert lizard community to habitat degradation: Do ideas about habitat specialists/generalists hold?

Impact of turbulence on riverine zooplankton: a mesocosm experiment

Responses of Ohio River and Lake Erie dreissenid molluscs to changes in temperature and turbidity

The use of landmarks to define territorial boundaries.

Effects of disease and plant competition on yield in monocultures and mixtures of two wheat cultivars