Cyclical Parthenogenesis Research Articles

Load frequency control performance enhancement of an electric vehicle integrated time-delay multi-microgrid system

ABSTRACT Frequency control in a microgrid (μG) is problematic due to low inertia of distributed generators (DGs) and uncertainty of the renewable energy source-dependent DGs. Consequently, deploying distributed storage units (DSUs) in a μG is crucial for quickly arresting frequency deviations. The electric vehicle (EV) technology, as DSU, is being preferred over conventional energy storage due to its lower cost and slower degradation rate, facilitating demand side response in a μG. The adoption of the EV technology necessitates an open communication infrastructure in the μG, with a pre-existing communication time delay (CTD). This article explores the impact of EV integration on load frequency control (LFC) performance of a multi-microgrid (MμG) system and determines an optimal CTD value simultaneously. A cyclical parthenogenesis algorithm-optimized 2DOF-FOPID controller is implemented to obtain dynamic responses of the MμG system. Simulation results reveal significant improvements in dynamic responses when integrating EVs in the MμG, with a 97.33% increase in objective function value. The recommended controller also outperforms standard controllers in terms of how quickly frequency and tie-line power variations settle down to zero. Thus, the proposed controller meets the LFC requirements. Robustness of the proposed LFC scheme is tested against parametric variations in the MμG system.

RpUGT344J7 is involved in the reproduction switch of Rhopalosiphum padi with holocyclic life cycle.

Many aphid species exhibit both cyclical parthenogenesis (CP) and the obligate parthenogenesis (OP) life history, which are genetically determined. In CP aphid lineages, the parthenogenetic individuals can switch from asexual to sexual reproduction quickly in response to environmental factors such as changes in photoperiod and temperature. However, the OP aphid lineages do not undergo sexual reproduction under any conditions. So far, mechanisms underlying the reproduction switch in CP aphids have not been fully elucidated. Rhopalosiphum padi, a serious worldwide insect pest of wheat, has both CP and OP lineages. Uridine diphosphate-glycosyltransferases (UGTs) are enzymes that participate in the metabolic detoxification of xenobiotics. Here, we identified 43 RpUGT genes from R. padi genome and transcriptome sequences, and found that: (1) the UGT content of the CP lineage was significantly higher than that in the OP lineage at the key time points when CP lineage mainly produce virginoparae, gynoparae, and males under inducing condition, while there were no significant difference under normal conditions; (2) RpUGT344J7 gene was highly expressed during the time points when CP lineages produce gynopara and males; (3) the critical time points for CP lineages to produce virginoparaee, gynoparae, and males were affected when the CP lineages were injected with dsRpUGT344J7; (4) the knockdown of RpUGT344J7 caused a significant reduction in the total number of virginoparae, gynoparae, and males in the offspring under inducing condition. The findings contribute to our understanding of the molecular mechanisms underlying the quick shift from asexual to sexual reproduction in aphid species.

DNA methylation machinery is involved in development and reproduction in the viviparous pea aphid (Acyrthosiphon pisum).

Epigenetic mechanisms, such as DNA methylation, have been proposed to mediate plastic responses in insects. The pea aphid (Acyrthosiphon pisum), like the majority of extant aphids, displays cyclical parthenogenesis - the ability of mothers to switch the reproductive mode of their offspring from reproducing parthenogenetically to sexually in response to environmental cues. The pea aphid genome encodes two paralogs of the de novo DNA methyltransferase gene, dnmt3a and dnmt3x. Here we show, using phylogenetic analysis, that this gene duplication event occurred at least 150 million years ago, likely after the divergence of the lineage leading to the Aphidomorpha (phylloxerans, adelgids and true aphids) from that leading to the scale insects (Coccomorpha) and that the two paralogs are maintained in the genomes of all aphids examined. We also show that the mRNA of both dnmt3 paralogs is maternally expressed in the viviparous aphid ovary. During development both paralogs are expressed in the germ cells of embryos beginning at stage 5 and persisting throughout development. Treatment with 5-azactyidine, a chemical that generally inhibits the DNA methylation machinery, leads to defects of oocytes and early-stage embryos and causes a proportion of later stage embryos to be born dead or die soon after birth. These phenotypes suggest a role for DNA methyltransferases in reproduction, consistent with that seen in other insects. Taking the vast evolutionary history of the dnmt3 paralogs, and the localisation of their mRNAs in the ovary, we suggest there is a role for dnmt3a and/or dnmt3x in early development, and a role for DNA methylation machinery in reproduction and development of the viviparous pea aphid.

Modelling suggests Wolbachia-induced cytoplasmic incompatibility in oak gall wasps with cyclical parthenogenesis.

Oak gall wasps typically exhibit a life cycle with one sexual and one asexual generation each year. These wasps can carry various endosymbionts, one of which is the maternally inherited bacterium Wolbachia that can induce several reproductive manipulations on its host. Cytoplasmic incompatibility (CI) has been described as the most prominent of these manipulations. CI leads to embryonic mortality in the hosts' offspring when infected males mate with either uninfected females or with females that harbour different Wolbachia strains. It has been hypothesized that Wolbachia can induce CI in oak gall wasps. To address this hypothesis, we derived a mathematical model to investigate the spread of a bacterial infection in naive populations and to determine the plausibility of CI occurrence. To validate our model, we used published data from Wolbachia-infected Belonocnema kinseyi populations in two approaches. Our first approach uses measurements of infection frequencies and maternal transmission in the sexual generation. For the second approach, we extended the model to compare predictions to estimates of mtDNA-haplotypes, which, like Wolbachia, are maternally inherited, and can therefore be associated with the infection. Both approaches indicate that CI is present in these populations. Our model can be generalized to investigate the occurrence of CI not only for oak gall wasps but also for other species.

Phylloxera and Aphids Show Distinct Features of Genome Evolution Despite Similar Reproductive Modes.

Genomes of aphids (family Aphididae) show several unusual evolutionary patterns. In particular, within the XO sex determination system of aphids, the X chromosome exhibits a lower rate of interchromosomal rearrangements, fewer highly expressed genes, and faster evolution at nonsynonymous sites compared with the autosomes. In contrast, other hemipteran lineages have similar rates of interchromosomal rearrangement for autosomes and X chromosomes. One possible explanation for these differences is the aphid's life cycle of cyclical parthenogenesis, where multiple asexual generations alternate with 1 sexual generation. If true, we should see similar features in the genomes of Phylloxeridae, an outgroup of aphids which also undergoes cyclical parthenogenesis. To investigate this, we generated a chromosome-level assembly for the grape phylloxera, an agriculturally important species of Phylloxeridae, and identified its single X chromosome. We then performed synteny analysis using the phylloxerid genome and 30 high-quality genomes of aphids and other hemipteran species. Unexpectedly, we found that the phylloxera does not share aphids' patterns of chromosome evolution. By estimating interchromosomal rearrangement rates on an absolute time scale, we found that rates are elevated for aphid autosomes compared with their X chromosomes, but this pattern does not extend to the phylloxera branch. Potentially, the conservation of X chromosome gene content is due to selection on XO males that appear in the sexual generation. We also examined gene duplication patterns across Hemiptera and uncovered horizontal gene transfer events contributing to phylloxera evolution.

Contrasting Evolutionary Patterns Between Sexual and Asexual Lineages in a Genomic Region Linked to Reproductive Mode Variation in the pea aphid.

Although asexual lineages evolved from sexual lineages in many different taxa, the genetics of sex loss remains poorly understood. We addressed this issue in the pea aphid Acyrthosiphon pisum, whose natural populations encompass lineages performing cyclical parthenogenesis (CP) and producing one sexual generation per year, as well as obligate parthenogenetic (OP) lineages that can no longer produce sexual females but can still produce males. An SNP-based, whole-genome scan of CP and OP populations sequenced in pools (103 individuals from 6 populations) revealed that an X-linked region is associated with the variation in reproductive mode. This 840-kb region is highly divergent between CP and OP populations (FST = 34.9%), with >2,000 SNPs or short Indels showing a high degree of association with the phenotypic trait. In OP populations specifically, this region also shows reduced diversity and Tajima's D, consistent with the OP phenotype being a derived trait in aphids. Interestingly, the low genetic differentiation between CP and OP populations at the rest of the genome (FST = 2.5%) suggests gene flow between them. Males from OP lineages thus likely transmit their op allele to new genomic backgrounds. These genetic exchanges, combined with the selection of the OP and CP reproductive modes under different climates, probably contribute to the long-term persistence of the cp and op alleles.

The Transcriptomic Signature of Cyclical Parthenogenesis.

Cyclical parthenogenesis, where females can engage in sexual or asexual reproduction depending on environmental conditions, represents a novel reproductive phenotype that emerged during eukaryotic evolution. The fact that environmental conditions can trigger cyclical parthenogens to engage in distinct reproductive modes strongly suggests that gene expression plays a key role in the origin of cyclical parthenogenesis. However, the genetic basis underlying cyclical parthenogenesis remains understudied. In this study, we characterize the female transcriptomic signature of sexual versus asexual reproduction in the cyclically parthenogenetic microcrustacean Daphnia pulex and Daphnia pulicaria. Our analyses of differentially expressed genes (DEGs), pathway enrichment, and gene ontology (GO) term enrichment clearly show that compared with sexual reproduction, the asexual reproductive stage is characterized by both the underregulation of meiosis and cell cycle genes and the upregulation of metabolic genes. The consensus set of DEGs that this study identifies within the meiotic, cell cycle, and metabolic pathways serves as candidate genes for future studies investigating how the two reproductive cycles in cyclical parthenogenesis are mediated at a molecular level. Furthermore, our analyses identify some cases of divergent expression among gene family members (e.g., doublesex and NOTCH2) associated with asexual or sexual reproductive stage, suggesting potential functional divergence among gene family members.

Transcriptomics and the origin of obligate parthenogenesis.

Despite the presence of obligately parthenogenetic (OP) lineages derived from sexual ancestors in diverse phylogenetic groups, the genetic mechanisms giving rise to the OP lineages remain poorly understood. The freshwater microcrustacean Daphnia pulex typically reproduces via cyclical parthenogenesis. However, some populations of OP D. pulex have emerged due to ancestral hybridization and introgression events between two cyclically parthenogenetic (CP) species D. pulex and D. pulicaria. These OP hybrids produce both subitaneous and resting eggs parthenogenetically, deviating from CP isolates where resting eggs are produced via conventional meiosis and mating. This study examines the genome-wide expression and alternative splicing patterns of early subitaneous versus early resting egg production in OP D. pulex isolates to gain insight into the genes and mechanisms underlying this transition to obligate parthenogenesis. Our differential expression and functional enrichment analyses revealed a downregulation of meiosis and cell cycle genes during early resting egg production, as well as divergent expression patterns of metabolism, biosynthesis, and signaling pathways between the two reproductive modes. These results provide important gene candidates for future experimental verification, including the CDC20 gene that activates the anaphase-promoting complex in meiosis.

Masculinization of the X-chromosome in aphid soma and gonads

Males and females share essentially the same genome but differ in their optimal values for many phenotypic traits, which can result in intra-locus conflict between the sexes. Aphids display XX/X0 sex chromosomes and combine unusual X chromosome inheritance with cyclical parthenogenesis. Theoretical and empirical works support the hypothesis that the large excess of male-biased genes observed on the aphid X chromosome compared to autosomes evolved in response to sexual conflicts, by restricting the products of sexually antagonistic alleles to the sex they benefits. However, whether such masculinization of the X affects all tissues (as expected if it evolved in response to sexual conflicts) or is limited to specific tissues remains an open question. Here, we measured gene expression in three different somatic and gonadic tissues of males, sexual females and parthenogenetic females of the pea aphid. We observed a masculinization of the X in each of the studied tissues, with male-biased genes being 2.5 to 3.5 more frequent on the X than expected. We also tested the hypothesis that gene duplication can facilitate the attenuation of conflicts by allowing gene copies to neo- or sub-functionalize and reach sex-specific optima. As predicted, X-linked copies of duplicated genes having their other copies on autosomes were more frequently male-biased (40.5% of the genes) than duplicated autosomal genes (6.6%) or X-linked single-copy genes (32.5%). These results highlight a peculiar pattern of expression of X-linked genes in aphids at the tissue level and provide further support for sex-biased expression as a mechanism to attenuate intra-locus sexual conflicts.

Chaotically Enhanced Meta-Heuristic Algorithms for Optimal Design of Truss Structures with Frequency Constraints

The natural frequencies of any structure contain useful information about the dynamic behavior of that structure, and by controlling these frequencies, the destructive effects of dynamic loads, including the resonance phenomenon, can be minimized. Truss optimization by applying dynamic constraints has been widely welcomed by researchers in recent decades and has been presented as a challenging topic. The main reason for this choice is quick access to dynamic information by examining natural frequencies. Also, frequency constraint relations are highly nonlinear and non-convex and have implicit variables, so using mathematical and derivative methods will be very difficult and time consuming. In this regard, the use of meta-heuristic algorithms in truss weight optimization with frequency constraints has good results, but with the introduction of form variables, these algorithms trap at local optima. In this research, by applying chaos map in meta-heuristic algorithms, suitable conditions have been provided to escape from local optima and access to global optimums. These algorithms include Chaotic Cyclical Parthenogenesis Algorithms (CCPA), Chaotic Biogeography-Based Optimization (CBBO), Chaotic Teaching-Learning-Based Optimization (CTLBO) and Chaotic Particle Swarm Optimization (CPSO), respectively. Also, by using different scenarios, a good balance has been achieved between the exploration and exploitation of the algorithms.

Aberrant ontogeneses and life cycles in Paraneoptera.

The paper is a third part of the themed issue “Aberrant cytogenetic and reproductive patterns in the evolution of Paraneoptera”, prepared by a Russian-Bulgarian research team on the basis of long-term collaborative studies. This chapter reviews different peculiar aberrations in the ontogenesis of Paraneoptera, such as the appearance of the quiescent apodal and/or arostrate instars, exuviatrial, pupillarial and pseudopupillarial development, cyclic parthenogenesis, etc. The material and methods, terminology and the nomenclature of the used taxonomic names are listed in the first chapter of the issue (Gavrilov-Zimin et al. 2021).

Progress in the characterization of insulin-like peptides in aphids: Immunohistochemical mapping of ILP4

Aphids were the first animals described as photoperiodic due to their seasonal switch from viviparous parthenogenesis to sexual reproduction (cyclical parthenogenesis) caused by the shortening of the photoperiod in autumn. This switch produces a single sexual generation of oviparous females and males that mate and lay diapausing cold-resistant eggs that can overcome the unfavourable environmental conditions typical of winter in temperate regions. Previous studies have hinted at a possible implication of two insulin-like peptides (ILP1 and ILP4) in the aphid seasonal response, changing their expression levels between different photoperiodic conditions. Moreover, in situ localization of their transcripts in particular neurosecretory cells (NSCs) in the aphid brain supported the idea that these neuropeptides could correspond to the formerly called virginoparin, an uncharacterized factor originally proposed to be transported directly to the aphid embryos to promote their development as parthenogenetic individuals. To further investigate the fate of these ILPs, we raised a specific antiserum against one of them (ILP4) and mapped this neuropeptide by immunohistochemistry (IHC) in Acyrthosiphon pisum and Megoura viciae aphids. Coincident with in situ localization, our results show that ILP4 is synthesized in two groups (one in each brain hemisphere) of four neurosecretory cells in the pars intercerebralis (NSC group I) and then it is transported outside the brain to the corpora cardiaca. From there, three nerves (two laterals and one medial) transport it to the abdomen. Although no precise site of release has been found, the terminations of these nerves near the germaria would be compatible with the proposal of a direct connection between group I of NSCs and the reproductive system by localized release. In addition, we detected some collateral arborizations originating from the eight NSCs going to the pars lateralis, where clock neurons and some photoreceptors have been previously localized, suggesting a possible communication between the circadian and photoperiodic systems.

Distribution and population trends of two New Zealand endemic aphids (Hemiptera, Aphididae, Aphidinae)

ABSTRACT Visual observations for colonies of Aphis healyi Cottier on Carmichaelia odorata Benth. bushes and Schizaphis sp. indet. on Aciphylla aurea W.R.B. Oliv. shrubs were made over several seasons at usually 4- to 8-week intervals (but seldom over winter) at two South Island, New Zealand sites (420 and 880 m above sea level, respectively). The presence of aphid parasitoid mummies was also noted. On several occasions, aphid samples were taken to verify species and identify morphs. Both aphid species appear to be monoecious (i.e. not alternating between woody and herbaceous plant hosts), with A. healyi exhibiting cyclical parthenogenesis and overwintering as eggs (i.e. holocyclic) and Schizaphis sp. indet. exhibiting year round parthenogenesis and overwintering as active morphs (i.e. anholocyclic). Aphis healyi colonies were found from December to May with the greatest numbers of colonies being found from December to February. Schizaphis sp. indet. colonies were found throughout the year, including mid-winter, with the greatest numbers of colonies usually being found from October to December. Updated distribution data indicate that both species are more widespread than previously reported, with A. healyi found from the Poor Knights Islands in the north to Southland in the south, and the Schizaphis sp. indet. on Aciphylla spp. found throughout the South Island but not the North Island. This short communication adds population, ecological and biological knowledge on these relatively poorly understood endemic aphid species from New Zealand that informs their conservation status.

Molecular Placement of an Outbreak-Causing Gall Wasp,Zapatella davisae(Hymenoptera: Cynipidae), with Comments on Phylogenetic Arrangements in the Tribe Cynipini

AbstractGall wasps (Hymenoptera: Cynipidae) have fascinated researchers for centuries due to the elaborate diversity of charismatic galls they produce, the presence of unique reproductive systems (e.g., a form of cyclical parthenogenesis), the possible convergent evolution of semiparasitic gall wasp forms (i.e., “inquilines”), and their multitrophic interactions. While many classifications for gall wasps have been proposed, recent DNA sequence efforts combined with taxonomic revisions are beginning to clarify the evolutionary relationships of this group. To date, however, a well resolved phylogeny is lacking, complicating the study of outbreak-causing pest species. Outbreaks by one such species, the black oak gall wasp, Zapatella davisae Buffington & Melika (Hymenoptera: Cynipidae: Cynipini), have led to extensive damage and mortality of black oaks, Quercus velutina L. (Fagales: Fagaceae), in the northeastern United States. Here we sequenced fragments of the nuclear ribosomal gene 28S, and the nuclear protein coding gene long-wavelength opsin from samples of Z. davisae collected on Cape Cod, MA, and Long Island, NY. Using these sequences and sequences previously published from the mitochondrial locus cytochrome b, we performed Bayesian and maximum likelihood multilocus phylogenetic reconstructions based on a concatenated alignment including species of gall wasps in the tribe Cynipini from which all three loci were present in the GenBank database. Confirming morphological work, we find that Z. davisae is most closely related to species in the genera Callirhytis and Neuroterus, and appears to be a basal member of the “Quercus” section of the tribe Cynipini. We find that recent generic reclassifications within the Cynipini have made great progress towards clarifying the taxonomic relationships of species of gall-inducing wasps in this tribe, and we comment on several classifications that require additional research.

Domain decomposition of finite element models utilizing eight meta-heuristic algorithms: A comparative study

In this paper, the k-median of a graph is used to decompose the domain (mesh) of the continuous two- and three-dimensional finite element models. The problem of k-median is stated as an optimization problem and is solved by utilizing eight robust meta-heuristic algorithms. The Artificial Bee Colony algorithm (ABC), Cyclical Parthenogenesis algorithm (CPA), Cuckoo Search algorithm (CS), Teaching-Learning Based Optimization algorithm (TLBO), Tug of War Optimization algorithm (TWO), Water Evaporation Optimization algorithm (WEO), Ray Optimization algorithm (RO), and Vibrating Particles System algorithm (VPS) constitute the set of algorithms that are employed in the present study. In order to tune the parameters of the meta-heuristics, the Taguchi method is used. The efficiency and robustness of the algorithms are investigated through two- and three- dimensional finite element models.

Optimal design of planar steel frame structures utilizing meta-heuristic optimization algorithms

Meta-heuristic algorithms are applied in optimization problems in a variety of fields, including engineering, economics, and computer science. In this paper, seven population-based meta-heuristic algorithms are employed for size optimization of two-dimensional steel frame structures. These algorithms consist of the Artificial Bee Colony algorithm, Big Bang-Big Crunch algorithm, Cyclical Parthenogenesis Algorithm, Cuckoo Search algorithm, Thermal Exchange Optimization algorithm, Teaching-Learning-Based Optimization algorithm, and Water Evaporation Optimization algorithm. Optimization aims to minimize the weight of rigid-jointed steel frame structures while satisfying some constraints on displacement and stress limits. The design is based on the requirements of the AISC Load and Resistance Factor Design (LRFD). The capability and robustness of the algorithms are investigated through three well-known steel frame benchmarks.

Population genetic structure and predominance of cyclical parthenogenesis in the bird cherry-oat aphid Rhopalosiphum padi in England.

Genetic diversity is the determinant for pest species’ success and vector competence. Understanding the ecological and evolutionary processes that determine the genetic diversity is fundamental to help identify the spatial scale at which pest populations are best managed. In the present study, we present the first comprehensive analysis of the genetic diversity and evolution of Rhopalosiphum padi, a major pest of cereals and a main vector of the barley yellow dwarf virus (BYDV), in England. We have used a genotyping‐by‐sequencing approach to study whether (a) there is any underlying population genetic structure at a national and regional scale in this pest that can disperse long distances; (b) the populations evolve as a response to environmental change and selective pressures; and (c) the populations comprise anholocyclic lineages. Individual R. padi were collected using the Rothamsted Insect Survey's suction‐trap network at several sites across England between 2004 and 2016 as part of the RIS long‐term nationwide surveillance. Results identified two genetic clusters in England that mostly corresponded to a North–South division, although gene flow is ongoing between the two subpopulations. These genetic clusters do not correspond to different life cycle types, and cyclical parthenogenesis is predominant in England. Results also show that there is dispersal with gene flow across England, although there is a reduction between the northern and southern sites with the south‐western population being the most genetically differentiated. There is no evidence for isolation by distance and other factors such as primary host distribution, uncommon in the south and absent in the south‐west, could influence the dispersal patterns. Finally, results also show no evidence for the evolution of the R. padi population, and it is demographically stable despite the ongoing environmental change. These results are discussed in view of their relevance to pest management and the transmission of BYDV.

Optimal Design of Reinforced Concrete Cantilever Retaining Walls Utilizing Eleven Meta-Heuristic Algorithms: A Comparative Study

In this paper, optimum design of reinforced concrete cantilever retaining walls is performed under static and dynamic loading conditions utilizing eleven population-based meta-heuristic algorithms. These algorithms consist of Artificial Bee Colony algorithm, Big Bang-Big Crunch algorithm, Teaching-Learning-Based Optimization algorithm, Imperialist Competitive Algorithm, Cuckoo Search algorithm, Charged System Search algorithm, Ray Optimization algorithm, Tug of War Optimization algorithm, Water Evaporation Optimization algorithm, Vibrating Particles System algorithm, and Cyclical Parthenogenesis Algorithm. Two well-known methods consisting of the Rankine and Coulomb methods are used to determine lateral earth pressures acting on cantilever retaining wall under static loading condition. In addition, Mononobe-Okabe method is employed for dynamic loading condition. The design is based on ACI 318-05 and the goal of optimization is to minimize the cost function of the cantilever retaining wall. The performance of the utilized algorithms is investigated through an optimization example of cantilever retaining wall. In addition, convergence histories of the algorithms are provided for better understanding of their performance.

A comprehensive epigenomic analysis of phenotypically distinguishable, genetically identical female and male Daphnia pulex

BackgroundDaphnia species reproduce by cyclic parthenogenesis involving both sexual and asexual reproduction. The sex of the offspring is environmentally determined and mediated via endocrine signalling by the mother. Interestingly, male and female Daphnia can be genetically identical, yet display large differences in behaviour, morphology, lifespan and metabolic activity. Our goal was to integrate multiple omics datasets, including gene expression, splicing, histone modification and DNA methylation data generated from genetically identical female and male Daphnia pulex under controlled laboratory settings with the aim of achieving a better understanding of the underlying epigenetic factors that may contribute to the phenotypic differences observed between the two genders.ResultsIn this study we demonstrate that gene expression level is positively correlated with increased DNA methylation, and histone H3 trimethylation at lysine 4 (H3K4me3) at predicted promoter regions. Conversely, elevated histone H3 trimethylation at lysine 27 (H3K27me3), distributed across the entire transcript length, is negatively correlated with gene expression level. Interestingly, male Daphnia are dominated with epigenetic modifications that globally promote elevated gene expression, while female Daphnia are dominated with epigenetic modifications that reduce gene expression globally. For examples, CpG methylation (positively correlated with gene expression level) is significantly higher in almost all differentially methylated sites in male compared to female Daphnia. Furthermore, H3K4me3 modifications are higher in male compared to female Daphnia in more than 3/4 of the differentially regulated promoters. On the other hand, H3K27me3 is higher in female compared to male Daphnia in more than 5/6 of differentially modified sites. However, both sexes demonstrate roughly equal number of genes that are up-regulated in one gender compared to the other sex. Since, gene expression analyses typically assume that most genes are expressed at equal level among samples and different conditions, and thus cannot detect global changes affecting most genes.ConclusionsThe epigenetic differences between male and female in Daphnia pulex are vast and dominated by changes that promote elevated gene expression in male Daphnia. Furthermore, the differences observed in both gene expression changes and epigenetic modifications between the genders relate to pathways that are physiologically relevant to the observed phenotypic differences.

In-field prevalence of resistant grain aphid <em>Sitobion avenae</em> (Fabricius)

A concerning development for Irish agriculture is the detection of partial resistance in the main aphid pest (Sitobion avenae) of cereal crops to the most widely used pyrethroid insecticide compound. The mechanism of this resistance, termed ‘knockdown resistance’ (kdr), affects pyrethroid binding and enables S. avenae to survive insecticide exposure. This partial resistance to insecticide means that S . avenae can continue to inflict feeding damage and transmit barley yellow dwarf virus (BYDV), which may carry a significant yield penalty. The incidence and persistence of resistant S. avenae in the Irish population is currently unknown. To address this knowledge gap, in-field sampling of S. avenae was carried out from 2016 to 2018 in the 11 major cereal-growing counties, and 621 cases of S. avenae were screened. Genotyping was used to screen S. avenae for kdr and to determine the diversity of clones in the resistant and susceptible genotypes, thus testing the hypothesis of resistance in a single dominant super-clone. The data were statistically analysed to determine annual variation in resistance levels. Findings revealed that resistant S. avenae are widespread across Ireland, occurring in all the major cereal-growing counties. Despite an initial high prevalence of resistant S. avenae (54%), matching levels detected in the UK, prevalence in Irish field populations appeared not to be increasing over the duration of this study, suggesting that pyrethroids remain largely effective at managing aphid populations. Resistance was detected in a single dominant SA3 super-clone, which may be explained by the loss of cyclical parthenogenesis as a potential impact of resistance alleles.