Application of the Red List Index as an indicator of habitat change

For the first time ever, the International Union for Conservation of Nature Red List Index for habitat types was calculated for an entire country, Finland. The RLIs were based on species threat assessments from 2000 and 2010 and included habitat definitions for all 10,131 species of 12 organism groups. The RLIs were bootstrapped to track statistically significant changes. The RLI changes of species grouped by habitats were negative for all habitat types except for forests and rural biotopes which showed a stable trend. Trends of beetles and true bugs were positive in rural and forest habitats. Other 16 observed trends of species group and habitat combinations were negative. Several trends observed were in accordance with studies focusing on particular taxa and habitats, and drivers for their change. This study demonstrates the usefulness of the RLI as a tool for observing habitat change based on species threat assessment data.     

Über die Untersuchungen von A. H. Blaauw,betreffend die Beziehung zwischen Lichtintensität und Beleuchtungsdauer bei der phototropischen Krümmung von Keimlingen vonAvena sativa

Ohne ZusammenfassungProceedings of the Meetings of Saturday September 26, 1908.Die vorliegende Übersetzung, zu der Herr Prof. Went mich gütigst autorisierte, rechtfertigt sich durch die in theoretischer, ganz besonders aber in methodologischer Hinsicht überaus wichtigen Ergebnisse Blaauws. Die Untersuchung bestätigt zunächst ein Gesetz, das der Übersetzer für die Abhängigkeit der Präsentationszeit von der Lichtintensität festgestellt hat (die diesbezügliche Abhandlung war Herrn Prof. Went zur Zeit, als er dieses Referat schrieb, noch nicht zu Gesicht gekommen), verfolgt aber diese Gesetzmäßigkeit innerhalb wesentlich weiterer Grenzen. Die Feststellung ganz besonders, daß bei entsprechend intensiver Beleuchtung die Präsentationszeit bis auf 1/1000 Sekunde sinkt, zusammengehalten mit den Tatsachen der feinen Unterschiedsempfind-lichkeit der Pflanzen (Wiesner) und der außerordentlich kurzen Perzeptions-zeit (Fitting), muß die reizphysiologische Methodik reformieren und sie zu ebenso exaktem Arbeiten anspornen, wie es bei psychophysischen Experimenten längst der Fall ist.     

Dissociable Perceptual Effects of Visual Adaptation

Neurons in the visual cortex are responsive to the presentation of oriented and curved line segments, which are thought to act as primitives for the visual processing of shapes and objects. Prolonged adaptation to such stimuli gives rise to two related perceptual effects: a slow change in the appearance of the adapting stimulus (perceptual drift), and the distortion of subsequently presented test stimuli (adaptational aftereffects). Here we used a psychophysical nulling technique to dissociate and quantify these two classical observations in order to examine their underlying mechanisms and their relationship to one another. In agreement with previous work, we found that during adaptation horizontal and vertical straight lines serve as attractors for perceived orientation and curvature. However, the rate of perceptual drift for different stimuli was not predictive of the corresponding aftereffect magnitudes, indicating that the two perceptual effects are governed by distinct neural processes. Finally, the rate of perceptual drift for curved line segments did not depend on the spatial scale of the stimulus, suggesting that its mechanisms lie outside strictly retinotopic processing stages. These findings provide new evidence that the visual system relies on statistically salient intrinsic reference stimuli for the processing of visual patterns, and point to perceptual drift as an experimental window for studying the mechanisms of visual perception.     

Sulfide induces phosphate release from polyphosphate in cultures of a marine Beggiatoa strain

Sulfur bacteria such as Beggiatoa or Thiomargarita have a particularly high capacity for storage because of their large size. In addition to sulfur and nitrate, these bacteria also store phosphorus in the form of polyphosphate. Thiomargarita namibiensis has been shown to release phosphate from internally stored polyphosphate in pulses creating steep peaks of phosphate in the sediment and thereby inducing the precipitation of phosphorus-rich minerals. Large sulfur bacteria populate sediments at the sites of recent phosphorite formation and are found as fossils in ancient phosphorite deposits. Therefore, it can be assumed that this physiology contributes to the removal of bioavailable phosphorus from the marine system and thus is important for the global phosphorus cycle. We investigated under defined laboratory conditions which parameters stimulate the decomposition of polyphosphate and the release of phosphate in a marine Beggiatoa strain. Initially, we tested phosphate release in response to anoxia and high concentrations of acetate, because acetate is described as the relevant stimulus for phosphate release in activated sludge. To our surprise, the Beggiatoa strain did not release phosphate in response to this treatment. Instead, we could clearly show that increasing sulfide concentrations and anoxia resulted in a decomposition of polyphosphate. This physiological reaction is a yet unknown mode of bacterial polyphosphate usage and provides a new explanation for high phosphate concentrations in sulfidic marine sediments.     

Genetic variation maintained in multilocus models of additive quantitative traits under stabilizing selection.

Stabilizing selection for an intermediate optimum is generally considered to deplete genetic variation in quantitative traits. However, conflicting results from various types of models have been obtained. While classical analyses assuming a large number of independent additive loci with individually small effects indicated that no genetic variation is preserved under stabilizing selection, several analyses of two-locus models showed the contrary. We perform a complete analysis of a generalization of Wright's two-locus quadratic-optimum model and investigate numerically the ability of quadratic stabilizing selection to maintain genetic variation in additive quantitative traits controlled by up to five loci. A statistical approach is employed by choosing randomly 4000 parameter sets (allelic effects, recombination rates, and strength of selection) for a given number of loci. For each parameter set we iterate the recursion equations that describe the dynamics of gamete frequencies starting from 20 randomly chosen initial conditions until an equilibrium is reached, record the quantities of interest, and calculate their corresponding mean values. As the number of loci increases from two to five, the fraction of the genome expected to be polymorphic declines surprisingly rapidly, and the loci that are polymorphic increasingly are those with small effects on the trait. As a result, the genetic variance expected to be maintained under stabilizing selection decreases very rapidly with increased number of loci. The equilibrium structure expected under stabilizing selection on an additive trait differs markedly from that expected under selection with no constraints on genotypic fitness values. The expected genetic variance, the expected polymorphic fraction of the genome, as well as other quantities of interest, are only weakly dependent on the selection intensity and the level of recombination.     

Chromosome counts in some Alchemilla species from north-east Anatolia

This paper presents the results of karyological analysis of seven Alchemilla species collected from north-east Anatolia, Turkey, belonging to Alchemilla sect. Alchemilla subsect. Heliodrosium ser. Vulgares and subsect. Calycanthum ser. Elatae and ser. Calycinae. The following chromosome numbers were determined: A. haraldi 2n = 85–105, A. heterophylla 2n = 85–97, A. hirtipedicellata 2n = 86–100, A. oriturcica 2n = 86–102, A. persica 2n = 78–99, A. procerrima 2n = 69–78 and A. trabzonica 2n = 78–88. The chromosome numbers of three of these seven species are presented for the first time.