Vegetation dynamics in abandoned crop fields on a Mediterranean island: Development of succession model and estimation of disturbance thresholds

This case study on the Sifnos island, Greece, assesses the main factors controlling vegetation succession following crop abandonment and describes the vegetation dynamics of maquis and phrygana formations in relation to alternative theories of secondary succession. Field survey data were collected and analysed at community as well as species level. The results show that vegetation succession on abandoned crop fields is determined by the combined effects of grazing intensity, soil and geological characteristics and time. The analysis determines the quantitative grazing thresholds that modify the successional pathway. Light grazing leads to dominance by maquis vegetation while overgrazing leads to phryganic vegetation. The proposed model shows that vegetation succession following crop abandonment is a complex multi-factor process where the final or the stable stage of the process is not predefined but depends on the factors affecting succession. An example of the use of succession models and disturbance thresholds as a policy assessment tool is presented by evaluating the likely vegetation impacts of the recent reform of the Common Agricultural Policy on Sifnos island over a 20–30-year time horizon.     

Conceiving a fetus for bone marrow donation: An ethical problem in prenatal diagnosis

We present a family who sought prenatal diagnosis in order to bear a healthy child to serve as an HLA–identical bone marrow donor for their son affected with Wiskott–Aldrich syndrome. They intended to abort HLA-incompatible fetuses who would have been unsuitable bone marrow donors. This case led us to conclude that prenatal diagnosis should not be used to benefit a third party or facilitate the conception or abortion of a fetus for the purpose of generating an organ for transplantation. The limits of parental autonomy and physician responsibility are discussed.     

Prenatal diagnosis of a new syndrome: Holoprosencephaly with hypokinesia

Markedly decreased fetal activity (akinesia/hypokinesia) is usually readily apparent to experienced mothers, and frequently this concern leads to attempts at prenatal diagnosis. We report prenatal diagnosis of two fetuses with congenital contractures, markedly decreased fetal movement, and microcephaly due to severe holoprosencephaly. Such familial recurrence to phenotypically normal parents suggests a newly recognized autosomal recessive or X-linked syndrome that is readily detectable by prenatal ultrasonography.     

Prenatal diagnosis of pseudo arylsulphatase a deficiency

Prenatal diagnosis was performed on a pregnancy at risk for metachromatic leukodystrophy (MLD) in a family with the pseudo arylsulphatase A deficiency trait. Extracts of cultured amniotic fluid cells were deficient in arylsulphatase A indicating that the fetus was either affected with MLD or had the benign pseudodeficiency trait. In the cerebroside sulphate loading test, the at risk cells hydrolysed sulphatide like control cultured amniotic fluid cells implying that the fetus had pseudodeficiency. The pregnancy was carried to term and a male child was delivered. Placenta, urine and fibroblasts had very low activities of arysulphatase A. However, no sulphatide could be detected in urine and growing fibroblasts responded normally in the cerebroside sulphate loading test, suggesting pseudodeficiency. At 29 months, the infant is healthy and shows no stigmata of MLD. The prediction based on the results of the cerebroside sulphate loading test on cultured amniotic fluid cells appeared to be borne out.     

46,XY/47,XY,+ 17p+ mosaicism in amniocytes associated with fetal abnormalities despite normal fetal blood karyotype

46,XY/47,XY, + 17p + mosaicism was found in two primary amniotic fluid cultures (AFCs). Fetal blood karyotype was normal, but ultrasonography revealed Dandy-Walker malformation and bilateral choroid plexus cysts. Following termination of pregnancy, fetal examination revealed post-axial polydactyly and neuroblastoma-in-situ affecting both adrenals in addition to the cerebellar abnormalities. Mosaicism for the aberrant cell line was confirmed in all fetal tissues sampled and in the placenta.     

Interstitial deletions without phenotypic effect: Prenatal diagnosis of a new family and brief review

A 39-year-old woman (G4P1SAB2) was referred for amniocentesis for advanced maternal age. An interstitial deletion of the G-dark band 11 pi 2 was found in the fetus. Blood from the mother and her previous son was cultured and the same deletion was found in both. The absence of phenotypic effect in this family further confirms that G-dark euchromatic deletions are compatible with a normal phenotype, and underlines the importance of checking familial karyotypes even when apparently unbalanced structural rearrangements are found at prenatal diagnosis.     

Biophysical energy analyses of non-market values of the Ebro Delta

Non-market values were estimated with energy analysis under four land cover scenarios in the Ebro Delta, Spain. The market value of agriculture, the primary use value, is compared. Conversion of the natural landscape to agricultural fields has resulted in a drop in total annual non-market value from $721 million in the pristine scenario to $11 million in the present scenario. The market value of the agricultural crops has risen over time, from $10 million to almost $52 million, contributing the major portion of the total value of the Delta. However, the rate of return has decreased from the pristine to the present delta, indicating that more energy is required to produce a smaller output. Energy analyses reveal that one form of value—non-market value—is being traded for another—market value.     

Using habitat suitability index and particle dispersion models for early detection of marine invaders.

Eradication and control of invasive species are often possible only if populations are detected when they are small and localized. To be efficient, detection surveys should be targeted at locations where there is the greatest risk of incursions. We examine the utility of habitat suitability index (HSI) and particle dispersion models for targeting sampling for marine pests. Habitat suitability index models are a simple way to identify suitable habitat when species distribution data are lacking. We compared the performance of HSI models with statistical models derived from independent data from New Zealand on the distribution of two nonindigenous bivalves: Theora lubrica and Musculista senhousia. Logistic regression models developed using the HSI scores as predictors of the presence/absence of Theora and Musculista explained 26.7% and 6.2% of the deviance in the data, respectively. Odds ratios for the HSI scores were greater than unity, indicating that they were genuine predictors of the presence/ absence of each species. The fit and predictive accuracy of each logistic model were improved when simulated patterns of dispersion from the nearest port were added as a predictor variable. Nevertheless, the combined model explained, at best, 46.5% of the deviance in the distribution of Theora and correctly predicted 56% of true presences and 50% of all cases. Omission errors were between 6% and 16%. Although statistical distribution models built directly from environmental predictors always outperformed the equivalent HSI models, the gain in model fit and accuracy was modest. High residual deviance in both types of model suggests that the distributions realized by Theora and Musculista in the field data were influenced by factors not explicitly modeled as explanatory variables and by error in the environmental data used to project suitable habitat for the species. Our results highlight the difficulty of accurately predicting the distribution of invasive marine species that exhibit low habitat occupancy and patchy distributions in time and space. Although the HSI and statistical models had utility as predictors of the likely distribution of nonindigenous marine species, the level of spatial accuracy achieved with them may be well below expectations for sensitive surveillance programs.     

Population dynamics of naturalised Manila clams <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> in British coastal waters

The Manila clam Ruditapes philippinarum was introduced to Poole Harbour (lat 50°N) on the south coast of England in 1988 as a novel species for aquaculture. Contrary to expectations, this species naturalised. We report on individual growth patterns, recruitment, mortality and production within this population. On the intertidal mudflats the abundance of clams (>5 mm in length) varied seasonally between 18 and 56 individuals m⁻². There appear to be two recruitment events per year and there were 6 year classes in the population. A mid-summer decline in abundance was partly due to increased mortality but probably also a result of down-shore migration in response to high water temperatures and the development of anoxic conditions. A winter fishery removes c 75% of clams of fishable size (maximum shell length ≥40 mm) and c 20% of the annual production. The fishery depresses the maximum age and size attained by the clams but appears to be sustainable. Clam mortality due to factors other than fishing is highest in late-winter to early spring. The growth of the clams is intermediate in comparison with many published studies but remarkably good given their intertidal position. As on the coasts of the Adriatic Sea, where the clam is also non-native, the Manila clam has thrived in a shallow, eutrophic, lagoon-like system on the English coast. While the Poole Harbour population is currently Europe’s most northerly reported self-sustaining, naturalised population, given forecasts of increasing air and sea temperatures it might be expected that this species will eventually spread to more sites around the coasts of Northern Europe with associated economic and ecological consequences.