A review of the phylogeny and classification of the Asteraceae

The Asteraceae are commonly divided into two large subfamilies, the Cichorioideae (syn. Lactucoideae; Mutisieae, Cardueae, Lactuceae, Vernonieae, Liabeae, Arctoteae) and the Asteroideae (Inuleae, Astereae, Anthemideae, Senecioneae, Calenduleae, Heliantheae, Eupatorieae). Recent phylogenetic analyses based on morphological and chloroplast DNA data conclusively show that the Mutisieae-Barnadesiinae are the sister group to the rest of the family and that the Asteroideae tribes form a monophyletic group. The Vernonieae and Liabeae are sister tribes and the Eupatorieae are nested within a paraphyletic Heliantheae; otherwise tribal interrelationships are still largely uncertain. The Mutisieae-Barnadesiinae are excluded from the Mutisieae and elevated to the new subfamily Barnadesioideae. The two subfamilies Barnadesioideae and Asteroideae are monophyletic, whereas the status of the Cichorioideae remains uncertain. Analyses of chloroplast DNA data support the monophyly of the Cichorioideae; however, morphological data indicate that the subfamily is paraphyletic. Further studies are needed to test the monophyly of the Cichorioideae, as well as to further resolve tribal interrelationships in the two larger subfamilies.     

Was ferrocyanide a prebiotic reagent?

Hydrogen cyanide is the starting material for a diverse array of prebiotic syntheses, including those of amino acids and purines. Hydrogen cyanide also reacts with ferrous ions to give ferrocyanide, and so it is possible that ferrocyanide was common in the early ocean. This can only be true if the hydrogen cyanide concentration was high enough and the rate of reaction of cyanide with ferrous ions was fast enough. We show experimentally that the rate of formation of ferrocyanide is rapid even at low concentrations of hydrogen cyanide in the pH range 6–8, and therefore an equilibrium calculation is valid. The equilibrium concentrations of ferrocyanide are calculated as a function of hydrogen cyanide concentration, pH and temperature. The steady state concentration of hydrogen cyanide depends on the rate of synthesis by electric discharges and ultraviolet light and the rate of hydrolysis, which depends on pH and temperature. Our conclusions show that ferrocyanide was a major species in the prebiotic ocean only at the highest production rates of hydrogen cyanide in a strongly reducing atmosphere and at temperatures of 0°C or less, although small amounts would have been present at lower hydrogen cyanide production rates. The prebiotic application of ferrocyanide as a source of hydrated electrons, as a photochemical replication process, and in semi-permeable membranes is discussed.     

Evolution of the biosynthesis of the branched-chain amino acids

The origin of the biosynthetic pathways for the branched-chain amino acids cannot be understood in terms of the backwards development of the present acetolactate pathway because it contains unstable intermediates. We propose that the first biosynthesis of the branched-chain amino acids was by the reductive carboxylation of short branched chain fatty acids giving keto acids which were then transaminated. Similar reaction sequences mediated by nonspecific enzymes would produce serine and threonine from the abundant prebiotic compounds glycolic and lactic acids. The aromatic amino acids may also have first been synthesized in this way, e.g. tryptophan from indole acetic acid. The next step would have been the biosynthesis of leucine from -ketoisovaleric acid. The acetolactate pathway developed subsequently. The first version of the Krebs cycle, which was used for amino acid biosynthesis, would have been assembled by making use of the reductive carboxylation and leucine biosynthesis enzymes, and completed with the development of a single new enzyme, succinate dehydrogenase. This evolutionary scheme suggests that there may be limitations to inferring the origins of metabolism by a simple back extrapolation of current pathways.     

A portrait of a sucker using landscape genetics: how colonization and life history undermine the idealized dendritic metapopulation

Dendritic metapopulations have been attributed unique properties by in silico studies, including an elevated genetic diversity relative to a panmictic population of equal total size. These predictions have not been rigorously tested in nature, nor has there been full consideration of the interacting effects among contemporary landscape features, colonization history and life history traits of the target species. We tested for the effects of dendritic structure as well as the relative importance of life history, environmental barriers and historical colonization on the neutral genetic structure of a longnose sucker (Catostomus catostomus) metapopulation in the Kogaluk watershed of northern Labrador, Canada. Samples were collected from eight lakes, genotyped with 17 microsatellites, and aged using opercula. Lakes varied in differentiation, historical and contemporary connectivity, and life history traits. Isolation by distance was detected only by removing two highly genetically differentiated lakes, suggesting a lack of migration–drift equilibrium and the lingering influence of historical factors on genetic structure. Bayesian analyses supported colonization via the Kogaluk's headwaters. The historical concentration of genetic diversity in headwaters inferred by this result was supported by high historical and contemporary effective sizes of the headwater lake, T‐Bone. Alternatively, reduced allelic richness in headwaters confirmed the dendritic structure's influence on gene flow, but this did not translate to an elevated metapopulation effective size. A lack of equilibrium and upstream migration may have dampened the effects of dendritic structure. We suggest that interacting historical and contemporary factors prevent the achievement of the idealized traits of a dendritic metapopulation in nature.     

A batch correction method for liquid chromatography–mass spectrometry data that does not depend on quality control samples

The need for reproducible and comparable results is of increasing importance in non-targeted metabolomic studies, especially when differences between experimental groups are small. Liquid chromatography–mass spectrometry spectra are often acquired batch-wise so that necessary calibrations and cleaning of the instrument can take place. However this may introduce further sources of variation, such as differences in the conditions under which the acquisition of individual batches is performed. Quality control (QC) samples are frequently employed as a means of both judging and correcting this variation. Here we show that the use of QC samples can lead to problems. The non-linearity of the response can result in substantial differences between the recorded intensities of the QCs and experimental samples, making the required adjustment difficult to predict. Furthermore, changes in the response profile between one QC interspersion and the next cannot be accounted for and QC based correction can actually exacerbate the problems by introducing artificial differences. “Background correction” methods utilise all experimental samples to estimate the variation over time rather than relying on the QC samples alone. We compare non-QC correction methods with standard QC correction and demonstrate their success in reducing differences between replicate samples and their potential to highlight differences between experimental groups previously hidden by instrumental variation.     

A Presence-Only Model of Suitable Roosting Habitat for the Endangered Indiana Bat in the Southern Appalachians

We know little about how forest bats, which are cryptic and mobile, use roosts on a landscape scale. For widely distributed species like the endangered Indiana bat Myotis sodalis, identifying landscape-scale roost habitat associations will be important for managing the species in different regions where it occurs. For example, in the southern Appalachian Mountains, USA, M. sodalis roosts are scattered across a heavily forested landscape, which makes protecting individual roosts impractical during large-scale management activities. We created a predictive spatial model of summer roosting habitat to identify important predictors using the presence-only modeling program MaxEnt and an information theoretic approach for model comparison. Two of 26 candidate models together accounted for >0.93 of AICc weights. Elevation and forest type were top predictors of presence; aspect north/south and distance-to-ridge were also important. The final average best model indicated that 5% of the study area was suitable habitat and 0.5% was optimal. This model matched our field observations that, in the southern Appalachian Mountains, optimal roosting habitat for M. sodalis is near the ridge top in south-facing mixed pine-hardwood forests at elevations from 260–575 m. Our findings, coupled with data from other studies, suggest M. sodalis is flexible in roost habitat selection across different ecoregions with varying topography and land use patterns. We caution that, while mature pine-hardwood forests are important now, specific areas of suitable and optimal habitat will change over time. Combining the information theoretic approach with presence-only models makes it possible to develop landscape-scale habitat suitability maps for forest bats.     

Feeding effects on the neuroendocrine regulated development of fat body mitochondria in the cockroach Blaberus discoidalis

Fat body mitochondria in male Blaberus discoidalis showed a stepwise three-fold development in succinoxidase activity during the first 10 days of adult life. Long-term corpora cardiaca deficiency or prevention of feeding by oral blockage prevented the third step in succinoxidase development. Starvation alone did not prevent the complete development. Administration of corpora cardiaca extracts to orally blocked animals stimulated the final development of succinoxidase activity. It is speculated that the mechanical acts of feeding stimulate neurosecretory activity which increases the metabolic capacity of the fat body through effects on mitochondriogenesis.     

Carbon Assimilation Characteristics of the Aquatic CAM Plant, Isoetes howellii

The relationship between malic acid production and carbon assimilation was examined in the submerged aquatic Crassulacean acid metabolism (CAM) plant, Isoetes howellii Engelmann. Under natural conditions free-CO₂ level in the water was highest at 0600 hours and ¹⁴CO₂ assimilation rates in I. howellii were also highest at this time. After 0900 hours there was a similar pattern in (a) rate of free-CO₂ depletion from the water, (b) reduction of carbon assimilation rates, and (c) rate of deacidification in leaves. Rates of daytime deacidification increased under CO₂-free conditions and as irradiance intensity increased. Nighttime CO₂ uptake was estimated to contribute one-third to one-half of the total daily gross carbon assimilation. CO₂ uptake, however, accounted for only one-third to one-half of the overnight malic acid accumulation. Internal respiratory CO₂ may be a substrate for a large portion of overnight acid accumulation as leaves incubated overnight without CO₂ accumulated substantial levels of malic acid. Loss of CAM occurred in emergent leaf tips even though submerged bases continued CAM. Associated with loss of CAM in aerial leaves was an increase in total chlorophyll, a/b ratio, and carotenoids, and a decrease in leaf succulence. δ¹³C values of I. howellii were not clearly distinguishable from those for associated non-CAM submerged macrophytes.