Geographic variations in Helleborus foetidus elaiosome lipid composition: implications for dispersal by ants

Summary. Geographic variations in the correspondence between diaspore phenotypes and disperser behavior are thought to determine the evolution of plant-animal dispersal mutualisms. Helleborus foetidus is a widely distributed plant in Western Europe, which seeds bear a lipid rich elaiosome attracting ant dispersers. Laboratory cross-tests were conducted to check the correspondence between diaspore phenotypes and ant preference in two localities of the Iberian Peninsula, Caurel and Cazorla, separated by 750 km. Diaspores from Caurel were systematically preferred to those from Cazorla by Formica lugubris (the major disperser at Caurel), and Aphaenogatser iberica and Camponotus cruentatus (both major dispersers at Cazorla). Further bioassays conducted on A. iberica only showed that differences in elaiosome traits were sufficient to explain ant preference. Separation of the lipid fractions composing the elaiosome revealed that triglycerides, diglycerides and free fatty acids were all dominated by oleic acid. The elaiosomes from Caurel contained relatively more free oleic acid but were less concentrated in linoleyl-containing triglycerides, free palmitic acid and free linoleic acid than those from Cazorla. The three lipid fractions were attractive to ants but dummies soaked with the free fatty acids extracted from Caurel were preferred to those from Cazorla. Taken together, these results reinforce the idea that oleic acid is a major releaser of seed collection by ants and suggest that geographic variations in free fatty acid composition affect the probability of diaspore removal by ants which in turn potentially determine plant demography.     

Emergence of increased division of labor as a function of group size

Empirical evidence suggests that division of labor in insect societies is positively related to group size both within and across taxa. Response threshold models (RTM) have been commonly used to analyze patterns of division of labor. However, these models have been explored empirically and theoretically for only a limited number of tasks, and few studies have examined predictions of the model as colony size and work availability change. We theoretically examine how group size influences division of labor using a fixed response-threshold model. We simultaneously explore how expected by-products of increased colony size, including demand (total work need relative to total work force available) and task number, affect this relationship. Our results indicate that both low demand and high task number positively influence division of labor. We suggest that these changes parallel what is observed within social groups as their size increases, and that, in part, the commonly observed increased division of labor with increasing group size is emergent.     

First trimester prenatal diagnosis of haemophilia A: Two years' experience

We evaluated the feasibility, reliability, and acceptability of prenatal diagnosis of haemophilia A by DNA analysis of chorionic villi. Twenty-two women at risk to transmit the abnormal gene were referred for prenatal diagnosis, two of them twice. Two of the 22 women appeared to be non-carriers by DNA analysis. In one of these women, the results were known only after chorionic villus sampling had been carried out. Thirteen of the twenty carriers were heterozygous for an intragenic (Bell or Xbal) marker; six women were only heterozygous for the extragenic DXS52 (Stl4) locus. One of the women was homozygous for all the presently known DNA markers within or closely linked with the factor VIII locus. Twelve of the 22 fetuses at risk were male, ten were female. Seven of the 12 male fetuses were shown to be affected and were subsequently aborted. Four male fetuses appeared to be not affected. In one case, the diagnosis was made by use of an extragenic marker. The woman rejected fetal blood sampling to confirm the diagnosis. After birth, a normal factor VIII level was found in three of the four cases. The fourth pregnancy is still continuing. In one of the 12 male fetuses, no diagnosis at the gene level was possible. DNA analysis is expected to provide maximum certainty as to the phenotype of the fetus for approximately 60 per cent of the women; for another 37 per cent a rate of misdiagnosis of 4–5 per cent applies. In only 3 per cent of the cases will no diagnosis at the gene level be possible as yet. The new possibility of a prenatal diagnosis in the first trimester of pregnancy enabled some of these women to have a family of their own and was appreciated in particular by the women who underwent fetoscopy in an earlier pregnancy.     

4-n-Nonylphenol and 17-beta estradiol may induce common DNA effects in developing barnacle larvae

There is a growing concern over the potential effects of environmental endocrine disrupters on both human and wildlife populations. However, to date, minimal research has been conducted to determine the effect of estrogens and xenoestrogens at the DNA level. In this study, we used the random amplified polymorphic DNA (RAPD) assay to evaluate the effects on the genomic DNA of barnacle larvae that had been exposed to 17beta-estradiol (E2) and low concentrations of 4-n-nonylphenol (NP). DNA effects include DNA damage as well as mutations and possibly other effects at the DNA level that can be induced by chemical or physical agents that directly and/or indirectly interact with genomic DNA. Not only did exposure to NP and E2 induce changes in RAPD profiles in the exposed barnacle larvae when compared to control patterns, but also, and more importantly, there were similarities in the RAPD modifications in the exposed populations that had been treated to either chemical. We propose that NP and E2 induced some common DNA effects in barnacle larvae and that these specific modifications in RAPD patterns may arise as a consequence of hot spot DNA damage (e.g. DNA adducts) and/or mutations (point mutations or genomic rearrangements). This could help to explain how xenoestrogens mimic the effects produced by natural estrogens. In conclusion, in the field of endocrine disruption, the study of DNA effects induced by estrogens and/or xenoestrogens warrants further investigation. Indeed, changes at the DNA levcl may be the precursors of some of the numerous effects reported at higher levels of biological organisation such as the feminization of males, developmental abnormalities, and infertility.     

Flood-risk management strategies for an uncertain future: living with Rhine River floods in The Netherlands?

Social pressure on alluvial plains and deltas is large, both from an economic point of view and from a nature conservation point of view. Gradually, flood risks increase with economic development, because the expected damage increases, and with higher dikes, because the flooding depth increases. Global change, changing social desires, but also changing views, require a revision of flood-risk management strategies for the long term. These should be based on resilience as opposed to the resistence strategy of heightening dikes. Resilience strategies for flood-risk management imply that the river is allowed to temporarily flood large areas, whereas the flood damage is minimized by adapting land use. Such strategies are thus based on risk management and 'living with floods' instead of on hazard control. For The Netherlands, one of the most densely populated deltas in the world, alternative resilience strategies have been elaborated and assessed for their hydraulic functioning and 'sustainability criteria'.     

Modelling of the life cycle of Chironomus species using an energy-based model

Little is known about the differences between the species of the genus Chironomus relatively to their life cycle strategies. This knowledge is however crucial to fully understand the response of the Chironomus community to field perturbations. Here, we proposed to study four Chironomus species by using an energy-based model to describe growth, emergence and reproduction. We used data from the literature for two species (Chironomus plumosus and Chironomus tentans) and data from our experiments for two other species (Chironomus prasinus and Chironomus riparius). We showed that our model is able to accurately describe the life-history attributes for all the species tested, which suggests that Chironomus species have the same fundamental characteristics (low maintenance energetic costs, isomorphism), which makes possible the building of a common modelling framework to assess effects of toxicants at individual and population level. The species showed a few differences relatively to the parameters of the models with possible consequences when assessing effects of chemicals on Chironomus community. For instance, due to differences in growth parameters, C. riparius population dynamics should be more sensitive to effects on individual growth than C. prasinus or C. plumosus ones.     

Living within fallen palm leaves: the discovery of an unknown Blommersia (Mantellidae: Anura) reveals a new reproductive strategy in the amphibians of Madagascar

We describe a new mantelline frog of the genus Blommersia found in rainforest in North East Madagascar, from the protected areas of Ambatovaky, Betampona, Masoala, and Zahamena. Blommersia angolafa n.sp. is a small frog, with a body size of 17–21 mm, expanded finger and toe tips, and colouration ranging from yellow to dark brown, with pale-bluish spots on the flanks and light tips of fingers and toes. A peculiar aspect characterising this new species is its novel life history and reproductive mode. Both sexes live and breed in a phytotelmic habitat of water accumulated within fallen prophylls and fallen leaf sheaths of at least three species of Dypsis palms. Within these phytotelmata, egg laying and complete larval development occur. Thus, B. angolafa n.sp. represents a new evolutionary lineage of Malagasy frogs in which phytotelmy is known. Up to now, reproduction in phytotelmata in Malagasy frogs has been reported for many cophyline microhylids, most species of Guibemantis, Mantella laevigata, and possibly in a still-undescribed species belonging to the genus Spinomantis. We consider the reproductive mode of B. angolafa as a derived character, having evolved from the more typical reproduction in lentic water bodies. The general scarcity of lentic habitats in Malagasy rainforests may have provided the conditions that favoured the evolution of this phytotelmic breeding strategy. The new species, being specialised to a habitat represented by a few selected Dypsis species, potentially suffers the selective exploitation of these palms.