Plant phylogeny drives arboreal caterpillar assemblages across the Holarctic

1. Assemblages of insect herbivores are structured by plant traits such as nutrient content, secondary metabolites, physical traits, and phenology. Many of these traits are phylogenetically conserved, implying a decrease in trait similarity with increasing phylogenetic distance of the host plant taxa. Thus, a metric of phylogenetic distances and relationships can be considered a proxy for phylogenetically conserved plant traits and used to predict variation in herbivorous insect assemblages among co‐occurring plant species.
2. Using a Holarctic dataset of exposed‐feeding and shelter‐building caterpillars, we aimed at showing how phylogenetic relationships among host plants explain compositional changes and characteristics of herbivore assemblages.
3. Our plant–caterpillar network data derived from plot‐based samplings at three different continents included >28,000 individual caterpillar–plant interactions. We tested whether increasing phylogenetic distance of the host plants leads to a decrease in caterpillar assemblage overlap. We further investigated to what degree phylogenetic isolation of a host tree species within the local community explains abundance, density, richness, and mean specialization of its associated caterpillar assemblage.
4. The overlap of caterpillar assemblages decreased with increasing phylogenetic distance among the host tree species. Phylogenetic isolation of a host plant within the local plant community was correlated with lower richness and mean specialization of the associated caterpillar assemblages. Phylogenetic isolation had no effect on caterpillar abundance or density. The effects of plant phylogeny were consistent across exposed‐feeding and shelter‐building caterpillars.
5. Our study reveals that distance metrics obtained from host plant phylogeny are useful predictors to explain compositional turnover among hosts and host‐specific variations in richness and mean specialization of associated insect herbivore assemblages in temperate broadleaf forests. As phylogenetic information of plant communities is becoming increasingly available, further large‐scale studies are needed to investigate to what degree plant phylogeny structures herbivore assemblages in other biomes and ecosystems.

     

Determination of 7-methylguanine, N2,N2-dimethylguanosine, and pseudouridine in ultrafiltrated serum of healthy adults by high-performance liquid chromatography

7-Methylguanine (m7Gua), N2,N2-dimethylguanosine (m2(2)Guo), and pseudouridine (psi) are degradation products from RNA turnover and can be used as markers for the whole-body turnover of mRNA-cap, tRNA, and rRNA (in healthy individuals, urinary excretion of these catabolites follows a regular pattern; the relative molar ratio of psi:m7Gua:m2(2)Guo is approximately 100:19:6). HPLC methods were developed to measure serum concentrations of these RNA catabolites after deproteinization of the samples by ultrafiltration through microcollodion bags with a nominal exclusion Mr of 12,400. For healthy adults the following values (mean +/- SD) were found: psi, 2760 +/- 460 nmol/liter (n = 10); m7Gua, 129.7 +/- 24.0 nmol/liter (n = 13); m2(2)Guo, 31.0 +/- 3.7 nmol/liter (n = 9). The relative molar ratio of these substances in serum derived from our data is approximately 100:4.7:1.1. 7-Methylguanosine (m7Guo) added to serum is to a large extent converted to the corresponding free base, m7Gua, the form which is excreted in urine.     

Accuracy of alternative representations for integrated biochemical systems

The Michaelis-Menten formalism often provides appropriate representations of individual enzyme-catalyzed reactions in vitro but is not well suited for the mathematical analysis of complex biochemical networks. Mathematically tractable alternatives are the linear formalism and the power-law formalism. Within the power-law formalism there are alternative ways to represent biochemical processes, depending upon the degree to which fluxes and concentrations are aggregated. Two of the most relevant variants for dealing with biochemical pathways are treated in this paper. In one variant, aggregation leads to a rate law for each enzyme-catalyzed reaction, which is then represented by a power-law function. In the other, aggregation produces a composite rate law for either net rate of increase or net rate of decrease of each system constituent; the composite rate laws are then represented by a power-law function. The first variant is the mathematical basis for a method of biochemical analysis called metabolic control, the latter for biochemical systems theory. We compare the accuracy of the linear and of the two power-law representations for networks of biochemical reactions governed by Michaelis-Menten and Hill kinetics. Michaelis-Menten kinetics are always represented more accurately by power-law than by linear functions. Hill kinetics are in most cases best modeled by power-law functions, but in some cases linear functions are best. Aggregation into composite rate laws for net increase or net decrease of each system constituent almost always improves the accuracy of the power-law representation. The improvement in accuracy is one of several factors that contribute to the wide range of validity of this power-law representation. Other contributing factors that are discussed include the nonlinear character of the power-law formalism, homeostatic regulatory mechanisms in living systems, and simplification of rate laws by regulatory mechanisms in vivo.     

cDNA cloning and sequencing of tarantula hemocyanin subunits

Summary Tarantula heart cDNA libraries were screened with synthetic oligonucleotide probes deduced from the highly conserved amino acid sequences of the two copper-binding sites, copper A and copper B, found in chelicerate hemocyanins. Positive cDNA clones could be obtained and four different cDNA types were characterized.     

Correlation between low CSA plasma concentration and severity of acute GvHD in bone marrow transplantation

Between 1982 and 1986 51 patients were treated with ciclosporin a (CSA) to prevent graft versus host disease (GvHD) after bone marrow transplantation (BMT). Major side effects of the drug were tremor, hypertension, hepatotoxicity and nephrotoxicity. Acute GvHD 0 degree to II degree occurred in 80% of our patients, and GvHD III degree and IV degree in 20% despite the use of CSA. Two to four days before the onset of GvHD, CSA serum levels were significantly lower on the average in patients who developed GvHD III degree and IV degree compared to the others. Our data indicate that plasma CSA concentrations higher than 250 ng/ml should be achieved to reduce the severity of GvHD after BMT.     

Bilateral brainstem connections of the rat supratrigeminal region

Efferent and afferent connections of the supratrigeminal region were studied in the rat using iontophoretically delivered horseradish peroxidase and Phaseolus vulgaris leuco-agglutinin. Projections of supratrigeminal efferents were found to the contralateral supratrigeminal region, to the ipsi- and contralateral trigeminal motor nuclei and the medullary reticular formation, and to the ipsilateral facial and hypoglossal motor nuclei. Neurons projecting to the supratrigeminal region were located in the contralateral supratrigeminal nucleus, in the ipsilateral mesencephalic trigeminal nucleus and bilaterally in the medullary reticular formation. This organization is discussed with respect to bilateral oral motor control mechanisms.     

Notes on the phylogeny of the nautiloidea

Critical notes on the monograph “Phylogeny of the Nautiloidea” by J. Dzik (1984), especially with respect to cephalopod material from the Lower Palaeozoic of Bohemia are presented. Oncocerid type of muscle scars in the Lower Devonian genusPtenoceras as well as succession of growth stages of the shell in Silurian genusSphooceras is figured.     

Cell cycles and growth laws: the CCC model

In the cell-cycle-with-control model (CCC model), cells have to satisfy a condition before they are allowed to pass a control point during G1. Different cycle durations within a cell population are explained by individual time spans needed to satisfy the passing condition. If the distribution of cycle durations is time invariant, the population will grow exponentially. However, if the average cycle duration becomes longer, while the population grows, non-exponential population growth results. Simple functions for the lengthening of the average cycle duration, like linear or exponential ones, yield the well-known growth laws found in the biological literature. The same functions can be represented by an "S-system" differential equation that was derived earlier as an approximation for biochemical systems with many fast reactions (metabolism) and one slow process (e.g. ageing).     

Interstitial fluid pressure changes in pregnant rats

In pregnant rats significant interstitial fluid pressure changes could be detected by means of capsules chronically implanted into the subcutaneous tissue. The capsular pressure increased significantly from a control value of -4.3 +/- 0.5 mmHg to -0.7 +/- 0.5 mmHg during the first period of pregnancy. Immediately before parturition the capsular pressure returned to the control level. During lactation the pressure rose as high as + 0.5 +/- 0.9 mmHg. After lactation the pressure returned again to the control value. By determining the extracellular fluid and plasma volume, as well as protein concentration in plasma and capsular fluid, the hydrostatic and colloid osmotic forces operating in the extracellular space could be analysed. It has been concluded that the observed capsular pressure changes during pregnancy are not solely of volumetric or colloid osmotic origin.     

Ecological and methodological drivers of non-stationarity in tree growth response to climate

Radial tree growth is sensitive to environmental conditions, making observed growth increments an important indicator of climate change effects on forest growth. However, unprecedented climate variability could lead to non-stationarity, that is, a decoupling of tree growth responses from climate over time, potentially inducing biases in climate reconstructions and forest growth projections. Little is known about whether and to what extent environmental conditions, species, and model type and resolution affect the occurrence and magnitude of non-stationarity. To systematically assess potential drivers of non-stationarity, we compiled tree-ring width chronologies of two conifer species, Picea abies and Pinus sylvestris, distributed across cold, dry, and mixed climates. We analyzed 147 sites across the Europe including the distribution margins of these species as well as moderate sites. We calibrated four numerical models (linear vs. non-linear, daily vs. monthly resolution) to simulate growth chronologies based on temperature and soil moisture data. Climate–growth models were tested in independent verification periods to quantify their non-stationarity, which was assessed based on bootstrapped transfer function stability tests. The degree of non-stationarity varied between species, site climatic conditions, and models. Chronologies of P. sylvestris showed stronger non-stationarity compared with Picea abies stands with a high degree of stationarity. Sites with mixed climatic signals were most affected by non-stationarity compared with sites sampled at cold and dry species distribution margins. Moreover, linear models with daily resolution exhibited greater non-stationarity compared with monthly-resolved non-linear models. We conclude that non-stationarity in climate–growth responses is a multifactorial phenomenon driven by the interaction of site climatic conditions, tree species, and methodological features of the modeling approach. Given the existence of multiple drivers and the frequent occurrence of non-stationarity, we recommend that temporal non-stationarity rather than stationarity should be considered as the baseline model of climate–growth response for temperate forests.