Phylogeny and biogeography of the Vitrinidae (Gastropoda: Stylommatophora)

The phylogeny of the Vitrinidae is reconstructed in a cladistic analysis based on characters of the genitalia, the copulation behaviour and the radula. The genera with an atrial stimulator turned out to be the earliest branches of the Vitrinidae, whereas the genera with a glandula amatoria form a monophyletic, taxonomically apomorphic group. The differences between the proposed phylogeny and previous hypotheses are discussed. The ancestral areas of the Vitrinidae and its sister group, the limacoid slugs Boettgerillidae–Limacidae–Agriolimacidae, are estimated using weighted ancestral area analysis. The Vitrinidae and the limacoid slugs might have originated by a vicariance event between Central Europe and the Near East. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 2002, 134 , 347–358.     

Coexistence of natural enemies in a multitrophic host–parasitoid system

Abstract.  1. This study explored the temporal and spatial aspects of coexistence over many generations in a multispecies host–parasitoid assemblage.
2. The long-term interaction between the cabbage root fly, Delia radicum (Diptera: Anthomyiidae), and two of its natural enemies, Trybliographa rapae (Hymenoptera: Fitigidae) and Aleochara bilineata (Coleoptera: Staphylinidae), in a cultivated field at Silwood Park over 19 years was explored.
3. Although time series showed that the populations were regulated, the impact of the natural enemies was highly variable. Within-year determinants showed that the spatial response of the specialist parasitoid, T. rapae , was predominantly independent of host density while A. bilineata acted simply as a randomly foraging generalist parasitoid.
4. These findings are compared and contrasted with an earlier investigation of the same system when only the first 9 years of the time series were available. This study demonstrated the potential of long-term field studies for exploring hypotheses on population regulation, persistence, and coexistence.     

Introducing the Multivariate Dale Model in Population‐Based Genetic Association Studies

Until recently, the most common parametric approaches to study the combined effects of several genetic polymorphisms located within a gene or in a small genomic region are, at the genotype level, logistic regressions and at the haplotype level, haplotype analyses. An alternative modeling approach, based on the case/control principle, is to regard exposures (e.g., genetic data such as derived from Single Nucleotide Polymorphisms – SNPs) as random and disease status as fixed and to use a marginal multivariate model that accounts for inter‐relationships between exposures. One such model is the multivariate Dale model. This model is based on multiple logistic regressions. That is why the model, applied in a case/control setting, leads to straightforward interpretations that are similar to those drawn in a classical logistic modeling framework. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ecology and biogeography of plant communities associated with the post Plio-Pleistocene relict Rhododendron ponticum subsp. baeticum in southern Spain

Aims Rhododendron ponticum L. is reputed to be a post Plio‐Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500‐m main transect in each site, along the stream or river course, in which we placed five 20‐m‐long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. ponticum individuals. Results Rhododendron ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.     

Nitrogen and Phosphorus in the Finnish Energy System, 1900–2003

In producing power, humans move the nutrients nitrogen (N) and phosphorus (P) from their long‐term geological and biological stocks and release or emit them in soil, water, and the atmosphere. In Finland, peat combustion is an important driver of N and P fluxes from the environment to human economy. The flows of N and P in the Finnish energy system were quantified with partial substance flow analysis, and the driving forces of emissions of nitrogen oxides (NOx) were analyzed using the ImPACT model. In the year 2000 in Finland, 140,000 tonnes of nitrogen entered the energy system, mainly in peat and hard coal. Combustion released an estimated 66,000 tonnes of N as nitrogen oxides (NOx) and nitrous oxides (N2O) and another 74,000 tonnes as elemental N2. Most of the emissions were borne in traffic. At the same time, 6,000 tonnes of P was estimated to enter the Finnish energy system, mostly in peat and wood. Ash was mainly used in earth construction and disposed in landfills; thus negligible levels of P were recycled back to nature. During the twentieth century, fuel‐borne input of N increased 20‐fold, and of P 8‐fold. In 1900–1950, the increasing use of hard coal slowly boosted N input, whereas wood fuels were the main carrier of P. Since 1970, the fluxes have been on the rise. NOx emissions leveled off in the 1980s, though, and then declined in conjunction with improvements in combustion technologies such as NOx removal (de‐NOx) technologies in energy production and catalytic converters in cars.     

Estimating woody and herbaceous vegetation cover from time series satellite observations

In this paper we test a method to estimate the tree and grass vegetation cover over Australia from satellite-derived normalized difference vegetation index (NDVI) time series (monthly 1981–91, ≈5 km pixels) observations. The evergreen cover is assumed to track along the base of the NDVI time series, which is assumed to be equivalent to the woody vegetation cover. The base of the NDVI time series is estimated using modifications to a classical econometric model (i.e. time series is the sum of trend, seasonal and random components). Estimates of the average evergreen component during 1982–85 and 1986–89 were generally consistent with known vegetation distributions. Changes in evergreen cover were largely restricted to the south-west and south-east of Australia. Those changes were largely the result of differences in rainfall between the two periods. The proposed method for estimating woody vegetation cover is found to be generally robust. However, there are some regions where the grass (or pasture) is mostly evergreen. Some possible refinements are proposed to handle such cases.     

Instrumental test to estimate a model of forecast yield: a non-parametric application to the pollen index in South Italy

A statistical test is described to verify the characteristics of the biological information contained in the dynamics of the flowering process. The test focuses on interactions between the pollen index and climatic variables to investigate if the biological indicator can synthesise the information of the pre-flowering phases. The multiple-regression model is built upon two pre-flowering climate macro-indicators extracted by Principal Component Analysis (PCA) and the optimised pollen index is obtained by non-parametric estimation. The empirical analysis is applied to 15 stations located in southern Italy in regions that have a longstanding tradition of olive production. Using the variance explained, we find that an optimised pollen index is fairly well predicted by the pre-flowering climatic data. We conclude that the optimised pollen index makes more parsimonious the modelling for predicting olive production.     

The biometry of gills of 0-group European flounder

The gill surface area of 0-group, post-metamorphic Pleuronectes flesus L. was examined using digital image analysis software and expressed in relation to body mass according to the equation log Y=loga+c logW ( a =239·02; c =0·723). The components that constitute gill area, total filament length, interlamellar space and unilateral lamellar area were measured. The measurement of the length of every filament on all eight arches showed that commonly used methods of calculation can lead to an under-estimation of up to 24% of total filament length. Direct measurements of unilateral lamellar area with digital image analysis showed that previously reported gill area data for the same species was over-estimated by as much as 58%. In addition, in this species the neglect of gill pouch asymmetry after metamorphosis, can bring about a 14% over-estimation of total gill area.