Investigating a flower-insect forager network in a mountain grassland community using pollen DNA barcoding

Faced with the decline of pollinators, it is relevant to strengthen our understanding of the whole plant-pollinator web in semi-natural grasslands that serve as refuges for pollinator populations. The aim of this study was to explore the diversity of flower-foraging insects involved in pollen transfer in mountain semi-natural grasslands. Insects actively collecting pollen and/or nectar were caught in spring in six mountain semi-natural grasslands displaying a floristic richness gradient. Individual determinations of insects were made at the finest possible taxonomic scale and pollen loads were removed from the insect body. Using next-generation DNA sequencing, pollens were identified through the ribosomal DNA cistron using the ITS2 database and the ITS plant rDNA cistron sequences from Genbank. A total of 236 flower-foraging insects were collected. Diptera represented 82% of the total catches distantly followed by Hymenoptera (15%) and Apoidea (bees) (11%). Visual observations revealed that Diptera foraged on 16 of the 21 flower species visited by insects. DNA metabarcoding showed that 82% (191) of all of the collected insects were carrying pollen and 44% (104) were carrying two genera of plants or more. Our results demonstrate that Diptera are potential key-pollinators in mountain semi-natural grasslands that cannot be overlooked by the scientific community. However difficulties of taxonomic determination due to severe shortage of experts for Diptera have to be urgently overcome. Further studies on the link between pollen transfer and actual pollination in a global change context are also required. Moreover, our results support the idea that DNA metabarcoding provides accurate information about the plants-insects networks but it also pointed out sensitive issues, especially the necessity to build reliable national barcode databases.     

M3 cholinoreceptors alter electrical activity of rat left atrium via suppression of L-type Ca<Superscript>2+</Superscript> current without affecting K<Superscript>+</Superscript> conductance

Electrophysiological effects produced by selective activation of M3 cholinoreceptors were studied in isolated left atrium preparations from rat using the standard sharp glass microelectrode technique. The stimulation of M3 receptors was obtained by application of muscarinic agonist pilocarpine (10^?5 M) in the presence of selective M2 antagonist methoctramine (10^?7 M). Stimulation of M3 receptors induced marked reduction of action potential duration by 14.4 ± 2.4% and 16.1 ± 2.5% of control duration measured at 50 and 90% of repolarization, respectively. This effect was completely abolished by selective M3 blocker 4-DAMP (10^?8 M). In isolated myocytes obtained from the rat left atrium, similar pharmacological stimulation of M3 receptors led to suppression of peak L-type calcium current by 13.9 ± 2.6% of control amplitude (measured at +10 mV), but failed to affect K⁺ currents I _to, I _Kur, and I _Kir. In the absence of M2 blocker methoctramine, pilocarpine (10^?5 M) produced stronger attenuation of I _CaL and induced an increase in I _Kir. This additive inward rectifier current could be abolished by highly selective blocker of K_ir3.1/3.4 channels tertiapin-Q (10^?6 M) and therefore was identified as I _KACh. Thus, in the rat atrial myocardium activation of M3 receptors leads to shortening of action potentials via suppression of I _CaL, but does not enhance the major potassium currents involved in repolarization. Joint stimulation of M2 and M3 receptors produces stronger action potential shortening due to M2-mediated activation of I _KACh.     

Effects of landscape features on gene flow of valley oaks (<Emphasis Type="Italic">Quercus lobata</Emphasis>)

Landscape features affect habitat connectivity and patterns of gene flow and hence influence genetic structure among populations. We studied valley oak (Quercus lobata), a threatened species of California (USA) savannas and oak woodlands, with a distribution forming a ring around the Central Valley grasslands. Our main goal was to determine the role of topography and land cover on patterns of gene flow and to test whether elevation or land cover forms stronger barriers to gene flow among valley oak populations. We sampled valley oaks in 12 populations across the range of this species, genotyped each tree at eight nuclear microsatellite loci, and created a series of resistance surfaces by assigning different resistance values to land cover type and elevation. We also estimated recent migration rates and evaluated them with regard to landscape features. There was a significant but weak relationship between Euclidian distance and genetic distance. There was no relationship between genetic distances and land cover, but a significant relationship between genetic distances and elevation resistance. We conclude that gene flow is restricted by high elevations in the northern part of the valley oak range and by high elevations and the Central Valley further south. Migration rate analysis indicated some gene flow occurring east–west but we suggest that the high connectivity in the northern Central Valley is facilitating the formation of these links. We predict that southern populations may become more differentiated in the future through genetic isolation and local adaptation taking place in the face of climate change.     

Osmotic stress decreases complexity underlying the electrophysiological dynamic in soybean

• Studies on plant electrophysiology are mostly focused on specific traits of single cells. Inspired by the complexity of the signalling network in plants, and by analogy with neurons in human brains, we sought evidence of high complexity in the electrical dynamics of plant signalling and a likely relationship with environmental cues.
• An EEG‐like standard protocol was adopted for high‐resolution measurements of the electrical signal in Glycine max seedlings. The signals were continuously recorded in the same plants before and after osmotic stimuli with a ?2 MPa mannitol solution. Non‐linear time series analyses methods were used as follows: auto‐correlation and cross‐correlation function, power spectra density function, and complexity of the time series estimated as Approximate Entropy (ApEn).
• Using Approximate Entropy analysis we found that the level of temporal complexity of the electrical signals was affected by the environmental conditions, decreasing when the plant was subjected to a low osmotic potential. Electrical spikes observed only after stimuli followed a power law distribution, which is indicative of scale invariance.
• Our results suggest that changes in complexity of the electrical signals could be associated with water stress conditions in plants. We hypothesised that the power law distribution of the spikes could be explained by a self‐organised critical state (SOC) after osmotic stress.

     

Phylogenetic analysis of the genus <Emphasis Type="Italic">Argia</Emphasis> Rambur, 1842 (Odonata: Coenagrionidae), based on morphological characters of larvae and mitochondrial DNA sequences

The study of the evolutionary interrelationships among the species encompassed in the Neotropical genus Argia (Zygoptera: Coenagrionidae) has been neglected. The goal of this study is to infer the phylogenetic relationships among 36 species of Argia Rambur, 1842, using complementary data sets (i.e., larval morphology and mitochondrial DNA). The morphological data set comprises 76% of the larvae currently described for this genus and includes 97 morphological characters. From those, 47 characters have not been previously used in taxonomic studies involving dragonflies’ larvae. This is the first cladistic study based on larvae morphology for species within the suborder Zygoptera. Data partitions were analyzed individually, as well as total evidence, using parsimony and Bayesian inference as criteria for optimal-tree selection. The results support the monophyly of the North American species of Argia. This genus can be identified by the combination of eight synapomorphies, four of which are exclusively found in Argia. According to the optimal trees, the individual data sets (i.e., morphology and DNA sequences) have a high level of homoplasy, resulting in soft polytomies and low support for several nodes. The specific relationships of the terminal units differ between the phylogenies; nonetheless, there is historical congruence among them. Within Argia, five clades were consistently recovered. Most of those clades have been identified, at least in part, in previous phylogenetic and taxonomic studies. Indubitably, the morphological characters from larvae have historical signal useful for cladistic and taxonomic inference. Therefore, it should be a priority to pay more attention to this source of characters.     

Biosorption of Cr(VI) by Ceratocystis paradoxa MSR2 Using Isotherm Modelling,Kinetic Study and Optimization of Batch Parameters Using Response Surface Methodology

This study is focused on the possible use of Ceratocystis paradoxa MSR2 native biomass for Cr(VI) biosorption. The influence of experimental parameters such as initial pH, temperature, biomass dosage, initial Cr(VI) concentration and contact time were optimized using batch systems as well as response surface methodology (RSM). Maximum Cr(VI) removal of 68.72% was achieved, at an optimal condition of biomass dosage 2g L⁻¹, initial Cr(VI) concentration of 62.5 mg L⁻¹ and contact time of 60 min. The closeness of the experimental and the predicted values exhibit the success of RSM. The biosorption mechanism of MSR2 biosorbent was well described by Langmuir isotherm and a pseudo second order kinetic model, with a high regression coefficient. The thermodynamic study also revealed the spontaneity and exothermic nature of the process. The surface characterization using FT-IR analysis revealed the involvement of amine, carbonyl and carboxyl groups in the biosorption process. Additionally, desorption efficiency of 92% was found with 0.1 M HNO₃. The Cr(VI) removal efficiency, increased with increase in metal ion concentration, biomass concentration, temperature but with a decrease in pH. The size of the MSR2 biosorbent material was found to be 80 μm using particle size analyzer. Atomic force microscopy (AFM) visualizes the distribution of Cr(VI) on the biosorbent binding sites with alterations in the MSR2 surface structure. The SEM-EDAX analysis was also used to evaluate the binding characteristics of MSR2 strain with Cr(VI) metals. The mechanism of Cr(VI) removal of MSR2 biomass has also been proposed.