Habitat variation,mutualism and predation shape the spatio‐temporal dynamics of tansy aphids

1. Spatially distributed resources can lead to the formation of metapopulations, where individual subpopulations are often small and can experience frequent local extinction events followed by recolonisation. An example of terrestrial metapopulations are specialised phytophagous insects on their patchily distributed host plants. 2. The present study investigated the population dynamics of a specialised aphid (Metopeurum fuscoviride) on its patchily distributed host plant (Tanacetum vulgare) and associated community of mutualistic ants and predators in a small‐scale field site. Furthermore, aphid habitat differences (plant size, C/N ratio, location and surrounding vegetation) were quantified, and seasonal timing and precipitation were considered. 3. Seasonal timing and precipitation both had effects on aphid colonisation, extinction events and aphid colony persistence. Towards the end of the season, and after higher precipitation, aphid colonisation events decreased and extinction events increased. Plant size and location as well as aphid within‐field dispersal determined the spatio‐temporal distribution of aphid colonies. 4. Mutualistic ants (Lasius niger and Myrmica rubra) increased the chance of establishment of aphid colonies. However, when M. rubra was tending, aphid colony persistence was reduced. Aphid persistence and extinction were dependent on aphid abundance, as a higher colony size reduced the probability of extinction by predation. 5. The results emphasise the importance of dispersal limitation, population growth and the presence of mutualists when studying the spatio‐temporal dynamics of tansy aphids, particularly in a small‐scale field site.     

Chloroplast DNA‐based studies in molecular ecology may be compromised by nuclear‐encoded plastid sequence

Ongoing genetic transfer from mitochondria and plastids into the nucleus is a well‐documented fact. While in metazoan molecular ecology the need for surveillance against pseudogene‐mediated artefacts when analysing mtDNA sequences is commonly accepted, no comparable measurements have been established for plastid‐based studies. We highlight the impact and management of nuclear mitochondrial insertions, argue that nuclear plastid sequences represent an underestimated but major factor in plant molecular ecology, and discuss potential avenues of remedy in chloroplast studies.     

Some Reactions of 4′-Thionucleosides and Their Sulfones

Abstract

We report interesting and novel reactions of 4′-thionucleosides and their sulfone derivatives when a good leaving group is present in the 5′-position. The results have important implications for the phosphorylation of these nucleoside analogues by standard chemical procedures. Possible mechanisms for these reactions are discussed.

     

Night-time sun-compass behaviour of honey bees at the equator

ABSTRACT. In accordance with the peculiarities of the sun's azimuthal path near the equator, African honey bees observed in their night-time dances apparently allowed for the azimuth moving backwards at night relative to its day-time movement. In several cases the bees evidently inferred the actual azimuthal position of the sun, rather than the one that would result from extrapolating a uniform movement of the sun.     

Aspects of Nutrition and the Metabolism of Copper in Isopods

Terrestrial immigrants from the sea have to cope with two importantnutritional problems: a shift in pathways of absorption, andthe altered availability of nutrients. The more terrestrialspecies of littoral crustaceans switch to food as the main sourceof water and salts. No serious difficulties accompany the oraluptake of mobile ions, but the vegetarians amongst the immigrantsare required to assume a new attitude with regard to the assimilationor heavier metals. Some important heavy elements, notably Cuand Zn, are soluble in sea water but form rather intractableorganic complexes in plant tissues. Herbivorous amphipods andisopods on land are incapable of extracting copper directlyfrom their primary food sources. To compensate for this shortcoming,help is enlisted from microorganisms, which render the copperpresent in ill-digested fecal material available to the crustaceans.Moreover, in terrestrial and intertidal herbivorous crustaceans—ascompared with their marine relatives—the storage capacityof the hepatopancreas, as well as the efficiency of Cu-assimilation,is augmented; compartmentalization of Cu-storage is more rigorouslycarried through; the movements of Cu and Zn within the bodyare more strictly regulated, copper, for example, being exchangedbetween different compartments in the course of endogenouslyor exogenously induced phases of the animal's life cycle.     

Aldolase and Actin Protect Rabbit Muscle Lactate Dehydrogenase from Ascorbate Inhibition

Muscle-type LDH (LDH-m4) activity is critical for efficient anaerobic glycolysis. The results here show that rabbit LDH-M4 is inhibited by concentrations of ascorbate normally found in tissues. Aldolase and muscle G-actin were found to protect and to reverse inhibitions of LDH-m4 by ascorbate. G-actins showed some species specificity. Myosin, tropomyosin and troponin from rabbit muscle and muscle proteins from other animal sources had no affect on the inhibitions by ascorbate. The substrate inhibition of LDH-m4 by pyruvate is partially relieved by the presence of aldolase and lowers the Km without affecting the Vm. G-actin under similar conditions has no affect. It is believed that these studies reflect some of the resting properties of glycolytic enzymes that bind and unbind to contractile elements. It is proposed that ascorbate facilitates the storage of glycogen in muscle at rest by inhibiting glycolysis.     

Unravelling the genetic complexity of sorghum seedling development under low‐temperature conditions

Sorghum is a promising alternative to maize for bioenergy production in Europe; however, its use is currently limited by poor adaptation to low temperatures during and after germination. We collected multi‐trait phenotype data under optimal and suboptimal temperatures in a genetically diverse recombinant inbred line (RIL) mapping population showing contrasting segregation patterns for pre‐ and post‐emergence chilling tolerance. Germination, emergence, seedling development, root architecture and seedling survival were assessed in two different seedlots. Emergence and root establishment were found to be the key determinants of development and survival under chilling stress. Highly interactive epistatic quantitative trait loci (QTL) hotspots, including a previously unknown QTL on Sb06 with a significant effect on prolonged chilling survival, were found to regulate different physiological mechanisms contributing to maintenance of growth and development despite the chilling temperatures. The major QTL regions harbour promising candidate genes with known roles in abiotic stress tolerance. Identification of loci in the QTL hotspot regions conferring maintenance of cell division and growth under early chilling stress represents a promising step towards breeding for successful establishment of sorghum in temperate climates.     

Detection and Prediction of Tooth Mobility During the Periodontitis Healing Process

The focus of the article is on a generic approach to prediction of a healing process based on automatic measurement and modelling of mechanical disease indicators. As a specific example the healing process after treatment of advanced periodontitis is characterised and predicted based on measurement of tooth mobility (TM). For the measurement a new mechatronic instrument was developed that includes a pneumatically driven probe with incorporated sensors of tooth displacement and loading force. TM is measured by a computer controlled data acquisition system and predicted by a non-parametric regression. Similarly as in the characterisation of technical processes, a measured sample is described by TM time series detected on a particular patient, while the regression is determined by a set of samples obtained from a group of patients following periodontal therapy. The influence of surgical access therapy and systemic administration of metronidazole as an adjunct to the mechanical treatment is demonstrated. For this purpose the average changes of tooth mobility are determined on variously treated subgroups. A new method of healing process prediction is demonstrated and its performance is described by a prediction quality.