High genetic and morphological diversity despite range contraction in the diploid Hieracium eriophorum (Asteraceae) endemic to the coastal sand dunes of south‐west France

Endemic plants inhabiting coastal sand dunes show augmented extinction risks due to the dynamic nature of dunes and strong human pressure on coastal areas. To investigate the survival strategies and threats to long‐term survival of such species, we combined genetic, morphological and biogeographical approaches, using the example of Hieracium eriophorum (Asteraceae) and its putative cryptic sister species H. prostratum, which are endemic to the longest coastal sand dune in Europe. An analysis of amplified fragment length polymorphism revealed high within‐population genetic variability, and slight isolation by distance was the only indication of genetic population structure. Thus, no signs of genetic threats to survival were found. Furthermore, genetic and morphometric data provided no evidence for the existence of two species. Therefore, we propose to synonymize H. prostratum with H. eriophorum and provide a nomenclatural overview with typification. Finally, an analysis of historical distribution records showed that, during the last 100 years, the species was lost from its range margins, where its habitat became fragmented. Taken together, our results suggest that one successful survival strategy of narrow endemics may be the achievement of large local population sizes on a small geographical scale, thus avoiding the genetic problems inherent to small and fragmented populations. Dune management policies should thus take care that the current tendencies to allow more erosion will not result in too severe fragmentation of the remaining continuous stretches of dune habitat. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 365–377.     

Impaired macrophage phagocytosis of bacteria in severe asthma

Background

Bacteria are frequently cultured from sputum samples of severe asthma patients suggesting a defect in bacterial clearance from the airway. We measured the capacity of macrophages from patients with asthma to phagocytose bacteria.

Methods

Phagocytosis of fluorescently-labelled polystyrene beads, Haemophilus influenzae or Staphylococcus aureus by broncholaveolar lavage alveolar macrophages (AM) and by monocyte-derived macrophages (MDM) from non-asthmatics, mild-moderate and severe asthmatic patients was assessed using fluorimetry.

Results

There were no differences in phagocytosis of polystyrene beads by AMs or MDMs from any of the subject groups. There was reduced phagocytosis of Haemophilus influenzae and Staphylococcus aureus in MDMs from patients with severe asthma compared to non-severe asthma (p < 0.05 and p < 0.01, respectively) and healthy subjects (p < 0.01and p < 0.001, respectively). Phagocytosis of Haemophilus influenzae and Staphylococcus aureus by AM was also reduced in severe asthma compared to normal subjects (p < 0.05). Dexamethasone and formoterol did not suppress phagocytosis of bacteria by MDMs from any of the groups.

Conclusions

Persistence of bacteria in the lower airways may result partly from a reduced phagocytic capacity of macrophages for bacteria. This may contribute to increased exacerbations, airway colonization and persistence of inflammation.     

Host specificity and reproductive success of yucca moths (Tegeticula spp. Lepidoptera: Prodoxidae) mirror patterns of gene flow between host plant varieties of the Joshua tree (Yucca brevifolia: Agavaceae)

Coevolution between flowering plants and their pollinators is thought to have generated much of the diversity of life on Earth, but the population processes that may have produced these macroevolutionary patterns remain unclear. Mathematical models of coevolution in obligate pollination mutualisms suggest that phenotype matching between plants and their pollinators can generate reproductive isolation. Here, we test this hypothesis using a natural experiment that examines the role of natural selection on phenotype matching between yuccas and yucca moths (Tegeticula spp.) in mediating reproductive isolation between two varieties of Joshua tree (Yucca brevifolia var. brevifolia and Y. brevifolia var. jaegeriana). Using passive monitoring techniques, DNA barcoding, microsatellite DNA genotyping, and sibship reconstruction, we track host specificity and the fitness consequences of host choice in a zone of sympatry. We show that the two moth species differ in their degree of host specificity and that oviposition on a foreign host plant results in the production of fewer offspring. This difference in host specificity between the two moth species mirrors patterns of chloroplast introgression from west to east between host varieties, suggesting that natural selection acting on pollinator phenotypes mediates gene flow and reproductive isolation between Joshua‐tree varieties.     

The influence of weather and microclimate on Dalbulus maidis (Homoptera: Cicadellidae) flight activity and the incidence of diseases within maize and bean monocultures and bicultures in tropical America

Mixed cropping systems in tropical America have been shown to be less prone than monocultures to damage from pathogens carried by insects. This finding formed the basis for a series of experiments conducted in Costa Rica to evaluate the hypothesis that mixed cropping systems create a physical environment that influences vector movement and consequently the spread of leafhopper-borne pathogens. The principle finding of the study is that both the mixture of plants and planting density have little influence on the spread of pathogens by Dalbulus maidis, an oligophagus leafhopper which prefers maize, within maize and bean single and mixed cropping systems. Leafhopper flight activity proved similar for high and low density monocultures and bicultures. The number of leafhoppers immigrating to and emigrating from a field appears dependent on the size of the field, not the density of maize plants. Single and mixed crops with the same density of maize plants were equally prone to damage by pathogens carried by leafhoppers. The lower percentage infection in high density than in low density maize treatments resulted from fewer vectors per plant in the former.     

EXTRACTING MORE INFORMATION FROM THE TRIANGLE TASK

In a recent paper Berglund et al. (1993) applied the triangle task in conjunction with economic incentives to assess the bias and sensitivity of panelists discriminating between food and beverage products. A re-examination of the data from that study casts doubt on their interpretation of the results. Detection theory analyses of performance in sensory difference tests are increasingly used in food science and, where appropriate, permit independent bias and sensitivity measures to be extracted from discrimination data without the additional costs associated with the economic incentives test.     

ADVANTAGES OF THE SAME-DIFFERENT METHOD OVER THE TRIANGULAR METHOD FOR THE MEASUREMENT OF TASTE DISCRIMINATION

The triangular method, the same-different rating method, and the standard same-different method were each used with 10 tasters to obtain estimates of the discriminability of two concentrations of a colorless beverage. There were no significant differences in d', an index of discriminability, among the three tasks. In the light of this parity, a choice amongst the methods should be driven by practical considerations. When receiver operating characteristics (ROCs) were fitted to the rating data, the model underlying published tables of d' was strongly supported, so that discriminability can be assessed from same-different data either by entering tables or by fitting ROC curves. Same-different methods appear more acceptable to tasters than the triangular method.     

Plasmodium lophurae: Membrane Proteins of Erythrocyte-free Plasmodia and Malaria-Infected Red Cells*

SYNOPSIS. Plasma membranes of normal duckling erythrocytes were prepared by blender homogenization and nitrogen decompression. Surface membrane vesicles of red cells infected with the avian malaria Plasmodium lophurae were produced by nitrogen decompression. Membranes of erythrocyte-free malaria parasites were removed from cytoplasmic constituents by Dounce homogenization. These membranes were collected by centrifugation in a sucrose step gradient and purified on a linear sucrose gradient. Red cell membranes had a buoyant density of 1.159 g/cm³, whereas plasmodial membranes banded at 2 densities: 1.110 g/cm³ and 1.158 g/cm³. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the isolated red cell membranes revealed 7 major protein bands with molecular weights (MW) ranging from 230,000 to 22,000, and 3 glycoprotein bands with MW of 160,000, 88,000 and 37,000. Parasite membranes also had 7 major bands with MW ranging from 100,000 to 22,000. No glycoproteins were identifiable in these membranes. The proteins of the surface membranes from infected red cells had MW similar to those from normal red cells; however, there was some evidence of a reduction in the amount of the high MW polypeptides. The red cell membrane contained 79 nmoles sialic acid/mg membrane protein, whereas plasmodial membranes had 8 nmoles sialic acid/mg membrane protein. The sialic acid content of the surface membranes of infected red cells was significantly smaller than that of normal cells. Lactoperoxidase-glucose oxidase-catalyzed iodination of intact normal and malaria-infected erythrocytes labeled 7 surface components. Although no observable differences in iodinatable proteins were seen in these preparations, there was a striking reduction in the iodinatability of erythrocytic membranes obtained from P. lophurae-infected cells. Erythrocyte-free plasmodia bound very little radioactive iodine; the small amount of radioactivity was distributed among 3 major bands with MW of 42,000, 32,000 and 28,000. It is suggested that the alterations of the surface of the P. lophurae-infected erythrocyte do not occur by a wholesale insertion of plasmodial membrane proteins into the red cell plasma membrane, but rather that there are parasite-mediated modifications of existing membrane polypeptides.     

Protein Synthesis by a Cell-Free Preparation from the Bird Malaria,Plasmodium lophurae*

SYNOPSIS. Cytoplasmic polyribosomes were isolated from the avian malaria parasite Plasmodium lophurae by lysis with 0.15% Triton X-100 followed by high speed centrifugation through a discontinuous sucrose gradient. Polyribosomes were protected from nuclease degradation using 100 μg/ml heparin or 50 μg/ml dextran sulfate. Cell-free incorporation of radioisotope-labeled amino acids required a pH 5 fraction (duck reticulocyte), Mg²⁺, and an energy-generating system. The protein synthesizing system was stimulated by the addition of polyuridylic acid. Optimum conditions for protein synthesis by the plasmodial system are described. The effects of drugs on the cell-free protein synthesizing system using duck reticulocyte and plasmodial ribosomes are reported.     

Isolation,Characterization and Synthesis of DNA from a Malaria Parasite*

SYNOPSIS. Methods for the isolation and purification of DNA from the intraerythrocytic stages of the avian malaria parasite Plasmodium lophurae are described. The DNA of P. lophurae was found to have a 19 mole-percent guanine plus cytosine (G+C) composition as determined by melting temperature and density measurements in CsCl gradients, whereas that of the host cell nucleus was 35 molepercent G+C. Synthesis of DNA by P. lophurae was studied by following the incorporation of P³² during the in vitro growth of plasmodia in infected cell suspension cultures. DNA synthesis was linear during the multiple nuclear divisions of a single growth cycle in highly synchronous cultures. Separation of P³² labeled parasite DNA from the DNA of the duck erythrocyte on CsCl gradients showed that only parasite DNA was synthesized.