Modelling time‐varying low‐temperature‐induced mortality rates for pupae of Tuta absoluta (Gelechiidae,Lepidoptera)

In a series of laboratory experiments, acclimated pupae of Tuta absoluta were exposed to various constant low temperatures in order to estimate their maximum survival times (Kaplan–Meier, Lt_99.99). A Weibull function was fitted to the data points, describing maximum survival time as a function of temperature. In another experiment at ?6°C, the progress of mortality increasing with exposure time was identified. These values were fitted by a sigmoidal function converging asymptotically to 100% mortality for very long exposure times. Analysing mortality data from the maximum survival experiment by a generalized linear model showed a significant common slope parameter (p < .001) that reveals parallelism of the survival curves at each temperature if a log time axis is used. These curves appear stretched (time scaled) if plotted with a nonlogarithmic time axis. By combining these mathematical relations, it was possible to calculate a species‐specific ‘mortality surface’ which exhibits mortalities, depending on temperature and duration of exposure. In order to accumulate hourly mortalities for courses of varying temperatures, an algorithm was developed which yields mortality values from that surface taking into account the attained mortality level. In validation experiments, recorded mortalities were compared against modelled mortalities. Prediction of mortality was partially supported by the model, but pupae experiencing intensely fluctuating temperatures showed decreased mortality, probably caused by rapid cold hardening during exposure. Despite this observation, mortality data converged to distinct levels very close to 100% depending on the intensity of temperature fluctuations that were characteristic for different types of experiments. The highest mortality limit occurred at intensely fluctuating temperatures in laboratory experiments. This constituted a benchmark that was not reached under various field conditions. Thus, it was possible to identify temperature limits for the extinction of field populations of Tuta absoluta pupae.     

Understanding extinction debts: spatio–temporal scales,mechanisms and a roadmap for future research

Extinction debt refers to delayed species extinctions expected as a consequence of ecosystem perturbation. Quantifying such extinctions and investigating long‐term consequences of perturbations has proven challenging, because perturbations are not isolated and occur across various spatial and temporal scales, from local habitat losses to global warming. Additionally, the relative importance of eco‐evolutionary processes varies across scales, because levels of ecological organization, i.e. individuals, (meta)populations and (meta)communities, respond hierarchically to perturbations. To summarize our current knowledge of the scales and mechanisms influencing extinction debts, we reviewed recent empirical, theoretical and methodological studies addressing either the spatio–temporal scales of extinction debts or the eco‐evolutionary mechanisms delaying extinctions. Extinction debts were detected across a range of ecosystems and taxonomic groups, with estimates ranging from 9 to 90% of current species richness. The duration over which debts have been sustained varies from 5 to 570 yr, and projections of the total period required to settle a debt can extend to 1000 yr. Reported causes of delayed extinctions are 1) life‐history traits that prolong individual survival, and 2) population and metapopulation dynamics that maintain populations under deteriorated conditions. Other potential factors that may extend survival time such as microevolutionary dynamics, or delayed extinctions of interaction partners, have rarely been analyzed. Therefore, we propose a roadmap for future research with three key avenues: 1) the microevolutionary dynamics of extinction processes, 2) the disjunctive loss of interacting species and 3) the impact of multiple regimes of perturbation on the payment of debts. For their ability to integrate processes occurring at different levels of ecological organization, we highlight mechanistic simulation models as tools to address these knowledge gaps and to deepen our understanding of extinction dynamics.     

东太平洋赤道海域茎柔鱼的营养生态位和肠道微生物组成

掌握海洋生物的营养生态位特征及其应对环境变化的响应机制,对于评估渔业和气候变化对海洋生态系统功能的影响至关重要.茎柔鱼(Dosidicus gigas)是东太平洋重要的渔业经济物种,在生态系统中具有承上启下的重要生态作用.在气候变化的大背景下,掌握茎柔鱼应对气候变化的响应过程将有利于合理把控其资源状况.本研究采用稳定同...     

Ferrocene-based inhibitors of hepatitis C virus replication that target NS5A with low picomolar in vitro antiviral activity

An unprecedented series of organometallic HCV (hepatitis C virus) NS5A (nonstructural 5A protein) replication complex inhibitors that incorporates a 1,1′-ferrocenediyl scaffold was explored. This scaffold introduces the elements of linear flexibility and non-planar topology that are unconventional for this class of inhibitors. Data from 2-D NMR spectroscopic analyses of these complexes in solution support an anti (unstacked) arrangement of the pharmacophoric groups. Several complexes demonstrate single-digit picomolar in vitro activity in an HCV genotype-1b replicon system. One complex to arise from this investigation (10a) exhibits exceptional picomolar activity against HCV genotype 1a and 1b replicons, low hepatocellular cytotoxicity, and good pharmacokinetic properties in rat.     

Natural variation in Arabidopsis lyrata vernalization requirement conferred by a FRIGIDA indel polymorphism

Species share homologous genes to a large extent, but it isnot yet known to what degree the same loci have been targetsfor natural selection in different species. Natural variationin flowering time is determined to a large degree by 2 genes,FLOWERING LOCUS C and FRIGIDA, in Arabidopsis thaliana. Here,we examine whether FRIGIDA has a role in differences in floweringtime between and within natural populations of Arabidopsis lyrata,a close outcrossing perennial relative of A. thaliana. We found2 FRIGIDA sequence variants producing potentially functionalproteins but with a length difference of 14 amino acids. Thesevariants conferred a 15-day difference in flowering time inan association experiment in 2 Scandinavian populations. Thedifference in flowering time between alleles was confirmed withtransformation to A. thaliana. Because the north European late-floweringpopulations harbor both late- and early sequence variants atintermediate frequencies and the late-flowering variant is mostfrequent in the southern early flowering European population,other genetic factors must be responsible for the floweringtime differences between the populations. The length polymorphismoccurs at high frequencies also in several North American populations.The occurrence of functional variants at intermediate frequenciesin several populations suggests that the variation may be maintainedby balancing selection. This is in contrast to A. thaliana,where independent loss-of-function mutations at the FRIGIDAgene are responsible for differences between populations andlocal adaptation.     

TiLIA: a software package for image analysis of firefly flash patterns

As flash signaling patterns of fireflies are species specific, signal‐pattern analysis is important for understanding this system of communication. Here, we present time‐lapse image analysis (TiLIA), a free open‐source software package for signal and flight pattern analyses of fireflies that uses video‐recorded image data. TiLIA enables flight path tracing of individual fireflies and provides frame‐by‐frame coordinates and light intensity data. As an example of TiLIA capabilities, we demonstrate flash pattern analysis of the fireflies Luciola cruciata and L. lateralis during courtship behavior.     

Habitat use and its implications to functional morphology: niche partitioning and the evolution of locomotory morphology in Lake Tanganyikan cichlids (Perciformes: Cichlidae)

Animal locomotory morphology, i.e. morphological features involved in locomotion, is under the influence of a diverse set of ecological and behavioral factors. In teleost fish, habitat choice and foraging strategy are major determinants of locomotory morphology. In this study, we assess the influence of habitat use and foraging strategy on important locomotory traits, namely the size of the pectoral and caudal fins and the weight of the pectoral fin muscles, as applied to one of the most astonishing cases of adaptive radiation: the species flock of cichlid fishes in East African Lake Tanganyika. We also examine the course of niche partitioning along two main habitat axes, the benthic vs. limnetic and the sandy vs. rocky substrate axis. The results are then compared with available data on the cichlid adaptive radiation of neighbouring Lake Malawi. We find that pectoral fin size and muscle weight correlate with habitat use within the water column, as well as with substrate composition and foraging strategies. Niche partitioning along the benthic–limnetic axis in Lake Tanganyikan cichlids seems to follow a similar course as in Lake Malawi, while the course of habitat use with respect to substrate composition appears to differ between the cichlid assemblages of these two lakes.     

Real‐time PCR identification of the ambrosia beetles,Trypodendron domesticum (L.) and Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae)

The European hardwood ambrosia beetle (Trypodendron domesticum) and the striped ambrosia beetle (Trypodendron lineatum) are wood‐boring pests that can cause serious damage to lumber, resulting in a need for management of these pests in logging and lumber industries. Natural populations of ambrosia beetles exist throughout the world, but movement of ambrosia beetles into new habitats, particularly via international trade, can result in the establishment of invasive species that have the potential to spread into new territory. Efforts to monitor ambrosia beetle populations are time‐consuming and could be greatly enhanced by the use of molecular methods, which would provide accurate and rapid identification of potentially problematic species. Here, we present new real‐time PCR assays for the detection and identification of T. domesticum and T. lineatum. The methods described herein can be used with a variety of sampling strategies to enable timely and well‐informed decision‐making in efforts to control these ambrosia beetles.     

Factors influencing nitrate depletion in a rural stream

A mass balance procedure was used to analyze rates of nitrate depletion in three adjacent reaches of West Duffin Creek, Ontario, Canada. Daily nitrate losses in individual reaches were highly variable (0.5–24 kg N) during low and moderate stream flows in May–October, 1982–1985. Nitrate removal efficiency (nitrate loss as a % of nitrate input) showed a rapid exponential decline with increased nitrate inputs to each reach. Nitrate losses and nitrate removal efficiency also had a significant negative correlation with stream discharge. The association of large nitrate loads with high stream discharge reduced the nitrate removal capacity of the stream because of shorter residence times and a higher ratio of water volume to stream bed area. Water temperature exhibited a significant positive correlation with nitrate loss which may reflect increased denitrification at higher temperatures.Variations in nitrate losses and nitrate removal efficiency between the three reaches were highly influenced by differences in water residence time. Standarized nitrate losses with respect to water residence time revealed a longitudinal decline in nitrate depletion between the reaches which was associated with a downstream decrease in stream nitrate concentration and in the organic carbon content of fine textured sediments from pool habitats.     

Comparison of the Morphology Development of Polymer–Fullerene and Polymer–Polymer Solar Cells during Solution‐Shearing Blade Coating

In this work, the detailed morphology studies of polymer poly(3‐hexylthiophene‐2,5‐diyl) (P3HT):fullerene(PCBM) and polymer(P3HT):polymer naphthalene diimide thiophene (PNDIT) solar cell are presented to understand the challenge for getting high performance all‐polymer solar cells. The in situ X‐ray scattering and optical interferometry and ex situ hard and soft X‐ray scattering and imaging techniques are used to characterize the bulk heterojunction (BHJ) ink during drying and in dried state. The crystallization of P3HT polymers in P3HT:PCBM bulk heterojunction shows very different behavior compared to that of P3HT:PNDIT BHJ due to different mobilities of P3HT in the donor:acceptor glass. Supplemented by the ex situ grazing incidence X‐ray diffraction and soft X‐ray scattering, PNDIT has a lower tendency to form a mixed phase with P3HT than PCBM, which may be the key to inhibit the donor polymer crystallization process, thus creating preferred small phase separation between the donor and acceptor polymer.