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BACKGROUND: Cnaphalocrocis medinalis is one of the major rice insect pests in Asia. Chlorantraniliprole is one of the most important insecticides for the control of C. medinalis. In this study, a field‐resistant population and a susceptible strain of C. medinalis were used to evaluate the inheritance of chlorantraniliprole resistance and fitness costs in the field. RESULTS: The field‐resistant population (Cm‐RR) showed 128.4‐fold resistance to chlorantraniliprole compared with the susceptible strain (Cm‐SS). The dose–response of reciprocal cross progeny (F1 and F1′) showed no significant difference, which indicated the inheritance of resistance to chlorantraniliprole in C. medinalis was autosomal. The degrees of dominance (D) of resistance for F1 and F1′ were −0.19 and −0.05, respectively, indicating that the chlorantraniliprole resistance of C. medinalis was incompletely recessive inheritance. At the same time, significant differences between observed and expected mortalities of self‐cross (F2 and F2′) and backcross (BC and BC′) progenies suggested chlorantraniliprole resistance is controlled by multiple genes. Furthermore, the Cm‐RR population had a relative fitness of 0.32 with a substantially decreased pupation rate, emergence rate, fecundity, and substantially increased developmental time of larval and pupa stages. CONCLUSION: Current research showed that the inheritance of chlorantraniliprole resistance to C. medinalis was autosomal, incompletely recessive and multigene. The field‐resistant population had a relative fitness of 0.32 when compared with the susceptible strain. This study provided valuable information for facilitating the development of chlorantraniliprole resistance management strategies. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Simple Summary: Resistance to insecticides is one of the main factors that makes it difficult to control the diamondback moth, Plutella xylostella, on Brassica crops. Recurrent control failures lead to more frequent insecticide applications, use of higher doses, and decreased yield. This results in environmental pollution, increased population resistance, and economic loss. Studies that elucidate the characteristics of resistance are necessary to improve pest control strategies and overcome this problem. Resistance, in turn, carries a fitness cost, which impairs the biological characteristics, or fitness, of the resistant population compared to a susceptible population in environments without insecticides. Thus, the present study evaluated the fitness cost of resistance to lufenuron in a P. xylostella population, as well as the stability of this resistance in the resistant population without selection pressure for four generations. As a result, we observed that the resistant population demonstrated greater resistance than the susceptible population of P. xylostella, as well as a low fitness cost which was associated with lufenuron resistance. This information supports the adoption of strategies such as preserving refuge areas near crops for susceptible insects and natural enemies, helping to dilute resistance in the field, as well as other strategies. The diamondback moth (DBM), Plutella xylostella, is the main pest of Brassicas crops worldwide, and its recorded resistance to 101 active ingredients indicates it is difficult to control. The purpose of this study was to investigate the hypothesis that P. xylostella has fitness costs associated with its resistance to lufenuron, a chitin-synthesis inhibitor insecticide. Thus, concentration–mortality bioassays were performed for susceptible (REC-S), resistant (BZR-R) populations, their progenies F1 and F1′, and one established population without selection pressure (BZR-Rns) after four generations. A fertility life table was used to assess the biological performance of the REC-S and BZR-R. BZR-Rns of P. xylostella. The larval stage, longevity, and survival differed between populations. The reproductive rate (R0) was significantly lower in the F1 (♀R × ♂S) (28.19) and F1′ (♀S × ♂R) (34.06) progenies compared with their parents, but not with the relaxed BZR-Rns (39.39). The mean generation time (T), intrinsic rate of population growth (rm), and doubling time (DT) differed between REC-S and progenies, with fitness of 0.52 and 0.64 for F1 and F1′, respectively. Overall, the results suggest that the resistance of P. xylostella to lufenuron is stable and that low fitness costs appear to be associated with resistance to lufenuron, although heterozygotes showed lower fitness than their parents. Strategies such as preserving refuge areas, rotation of modes of action, etc., are essential for resistance management and prolonging the efficacy of control agents; this highlights the importance of integrated insecticide resistance management. [ABSTRACT FROM AUTHOR]

In its initial form, the expensive son hypothesis postulates that sons from male‐biased sexually dimorphic species require more food during growth than daughters, which ultimately incur fitness costs for mothers predominantly producing and rearing sons. We first dissect the evolutionary framework in which the expensive son hypothesis is rooted, and we provide a critical reappraisal of its differences from other evolutionary theories proposed in the field of sex allocation. Then, we synthesize the current (and absence of) support for the costs of producing and rearing sons on maternal fitness components (future reproduction and survival). Regarding the consequences in terms of future reproduction, we highlight that species with pronounced sexual size dimorphism display a higher cost of sons than of daughters on subsequent reproductive performance, at least in mammals. However, in most studies, the relative fitness costs of producing and rearing sons and daughters can be due to sex‐biased maternal allocation strategies rather than differences in energetic demands of offspring, which constitutes an alternative mechanism to the expensive son hypothesis stricto sensu. We observe that empirical studies investigating the differential costs of sons and daughters on maternal survival in non‐human animals remain rare, especially for long‐term survival. Indeed, most studies have investigated the influence of offspring sex (or litter sex ratio) at year T on survival at year T + 1, and they rarely provide a support to the expensive son hypothesis. On the contrary, in humans, most studies have focused on the relationship between proportion of sons and maternal lifespan, but these results are inconsistent. Our study highlights new avenues for future research that should provide a comprehensive view of the expensive son hypothesis, by notably disentangling the effects of offspring behaviour from the effect of sex‐specific maternal allocation. Moreover, we emphasize that future studies should also embrace the mechanistic side of the expensive son hypothesis, largely neglected so far, by deciphering the physiological pathways linking son's production to maternal health and fitness. [ABSTRACT FROM AUTHOR]

Climate change is associated with increased mean temperatures and amplitudes manifesting both acutely and chronically, triggering organism stress responses that confer fitness costs and/or benefits. The larger grain borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is an invasive postharvest agricultural pest. While host shift is its well‐known potential invasive mechanism, how repeated intergenerational stress environments may influence offspring phenotypes is largely unknown. We thus evaluated physiological and ecological performance of LGB following repeated intergenerational acute heat acclimation to insinuate its likely responses to projected increased bouts of heat stress associated with climate change. Parental colonies were acutely heat‐acclimated separately at 35°C and 38°C; 80% RH for 2 h in climate chambers and released onto sterilized maize grain at optimal conditions (32°C, 80% RH). The F1 progenies were, respectively, acclimated at the same conditions and incubated to F2 generation. We then evaluated physiological and ecological performance under optimal conditions across parental, F1 and F2 generations. Our results showed that plasticity was highly trait dependent, and that acclimation did not affect F1 and F2 critical thermal maxima, but did improve critical thermal minima. However, while acclimation improved heat knockdown time at F1, repeated acclimation significantly reduced heat knockdown times at F2, suggesting plasticity erosion with generational repeated acclimations. Acute acclimation negatively affected ecological performance of F1 generations although this was restored with repeated acclimation in F2 populations. Our results suggest that the LGB may inflict more economic damage with repeated heat stress due to generational adaptation to temperature stress. The results contribute to knowledge on pest forecasting modelling under changing climates and provides a framework for phytosanitary adjustments in heat treatment protocols for international grain trade. [ABSTRACT FROM AUTHOR]

An introduction to a novel habitat represents a challenge to plants because they likely would face new interactions and possibly different physical context. When plant populations arrive to a new region free from herbivores, we can expect an evolutionary change in their defense level, although this may be contingent on the type of defense, resistance or tolerance, and cost of defense. Here, we addressed questions on the evolution of tolerance to damage in non-native Spanish populations of Datura stramonium by means of two comparative greenhouse experiments. We found differences in seed production, specific leaf area, and biomass allocation to stems and roots between ranges. Compared to the Mexican native populations of this species, non-native populations produced less seeds despite damage and allocate more biomass to roots and less to stems, and had higher specific leaf area values. Plasticity to leaf damage was similar between populations and no difference in tolerance to damage between native and non-native populations was detected. Costs for tolerance were detected in both regions. Two plasticity traits of leaves were associated with tolerance and were similar between regions. These results suggest that tolerance remains beneficial to plants in the non-native region despite it incurs in fitness costs and that damage by herbivores is low in the non-native region. The study of the underlying traits of tolerance can improve our understanding on the evolution of tolerance in novel environments, free from plants' specialist herbivores. [ABSTRACT FROM AUTHOR]

The increase in bacterial antibiotic resistance poses a significant threat to the effectiveness of antibiotics, and there is growing evidence suggesting that global warming may speed up this process. However, the direct influence of temperature on the development of antibiotic resistance and the underlying mechanisms is not yet fully understood. Here we show that antibiotic resistance exhibits a nonlinear response to elevated temperatures under the combined stress of temperatures and antibiotics. We find that the effectiveness of gatifloxacin against Escherichia coli significantly diminishes at 42 °C, while resistance increases 256-fold at 27 °C. Additionally, the increased transcription levels of genes such as marA, ygfA, and ibpB with rising temperatures, along with gene mutations at different sites, explain the observed variability in resistance patterns. These findings highlight the complexity of antibiotic resistance evolution and the urgent need for comprehensive studies to understand and mitigate the effects of global warming on antibiotic resistance.

Bacillus thuringiensis (Bt) toxins are potential alternatives to synthetic insecticides for the control of lepidopteran pests. However, the evolution of resistance in some insect pest populations is a threat and can reduce the effectiveness of Bt toxins. In this review, we summarize the results of 161 studies from 20 countries reporting field and laboratory-evolved resistance, cross-resistance, and inheritance, mechanisms, and fitness costs of resistance to different Bt toxins. The studies refer mainly to insects from the United States of America (70), followed by China (31), Brazil (19), India (12), Malaysia (9), Spain (3), and Australia (3). The majority of the studies revealed that most of the pest populations showed susceptibility and a lack of cross-resistance to Bt toxins. Factors that delay resistance include recessive inheritance of resistance, the low initial frequency of resistant alleles, increased fitness costs, abundant refuges of non-Bt, and pyramided Bt crops. The results of field and laboratory resistance, cross-resistance, and inheritance, mechanisms, and fitness cost of resistance are advantageous for predicting the threat of future resistance and making effective strategies to sustain the effectiveness of Bt crops. [ABSTRACT FROM AUTHOR]

Antibiotic resistance genes (ARGs) benefit host bacteria in environments containing corresponding antibiotics, but it is less clear how they are maintained in environments where antibiotic selection is weak or sporadic. In particular, few studies have measured if the direct effect of ARGs on host fitness is fixed or if it depends on the host strain, perhaps marking some ARG–host combinations as selective refuges that can maintain ARGs in the absence of antibiotic selection. We quantified the fitness effects of six ARGs in 11 diverse Escherichia spp. strains. Three ARGs (blaTEM-116, cat and dfrA5, encoding resistance to β-lactams, chloramphenicol, and trimethoprim, respectively) imposed an overall cost, but all ARGs had an effect in at least one host strain, reflecting a significant strain interaction effect. A simulation predicts these interactions can cause the success of ARGs to depend on available host strains, and, to a lesser extent, can cause host strain success to depend on the ARGs present in a community. These results indicate the importance of considering ARG effects across different host strains, and especially the potential of refuge strains to allow resistance to persist in the absence of direct selection, in efforts to understand resistance dynamics. [ABSTRACT FROM AUTHOR]

Drosophila remains a pre-eminent insect model system for host–virus interaction, but the host range and fitness consequences of the drosophilid virome are poorly understood. Metagenomic studies have reported approximately 200 viruses associated with Drosophilidae, but few isolates are available to characterize the Drosophila immune response, and most characterization has relied on injection and systemic infection. Here, we use a more natural infection route to characterize the fitness effects of infection and to study a wider range of viruses. We exposed laboratory Drosophila melanogaster to 23 naturally occurring viruses from wild-collected drosophilids. We recorded transmission rates along with two components of female fitness: survival and the lifetime number of adult offspring produced. Nine different viruses transmitted during contact with laboratory D. melanogaster, although for the majority, rates of transmission were less than 20%. Five virus infections led to a significant decrease in lifespan (D. melanogaster Nora virus, D. immigrans Nora virus, Muthill virus, galbut virus and Prestney Burn virus), and three led to a reduction in the total number of offspring. Our findings demonstrate the utility of the Drosophila model for community-level studies of host–virus interactions, and suggest that viral infection could be a substantial fitness burden on wild flies. [ABSTRACT FROM AUTHOR]

Bacteriophages exert strong selection on their bacterial hosts to evolve resistance. At the same time, the fitness costs on bacteria following phage resistance may change their virulence, which may affect the therapeutic outcomes of phage therapy. In this study, we set out to assess the costs of phage resistance on the in vitro virulence of priority 1 nosocomial pathogenic bacterium, Acinetobacter baumannii. By subjecting phage-resistant variant Ev5-WHG of A. baumannii WHG40004 to several in vitro virulence profiles, we found that its resistance to phage is associated with reduced fitness in host microenvironments. Also, the mutant exhibited impaired adhesion and invasion to mammalian cells, as well as increased susceptibility to macrophage phagocytosis. Furthermore, the whole-genome sequencing of the mutant revealed that there exist multiple mutations which may play a role in phage resistance and altered virulence. Altogether, this study demonstrates that resistance to phage can significantly alter phenotypes associated with virulence in Acinetobacter baumannii. [ABSTRACT FROM AUTHOR]

The pine wood nematode (PWN) uses several Monochamus species as vehicles, through a temporary hitchhiking process known as phoresy, enabling it to access new host plant resources. Monochamus saltuarius acts as a new and major vector of the PWN in Northeastern China, showing lower PWN carrying capacity and a shorter transmission cycle compared to established vectors. The apparently altered symbiotic relationship offers an interesting area for researching the costs and adaptions involved in nematode–beetle, a specialized phoresy. We analyzed the response and fitness costs of M. saltuarius through physiological measurements and transcriptomics. The PWN exerted adverse repercussions on the growth and development of M. saltuarius. The PWN accelerated larval development into pupae, while beetle adults carrying the PWN exhibited an elevated abnormality rate and mortality, and reduced starvation resistance. During the pupal stage, the expression of growth-related genes, including ecdysone-inducible genes (E74EA), cuticle proteins, and chitin genes (CHTs), markedly increased. Meanwhile, the induced immune response, mainly by the IMD and Toll signaling pathways, could be a contributing factor to adult abnormality and mortality. Adult gonads and trachea exhibited enrichment in pathways related to fatty acid elongation, biosynthesis, and metabolism. FASN, ELOVL, and SCD possibly contributed to resistance against PWN. Our research indicated that phoretic interactions between vector beetles and PWN vary throughout the vector's lifespan, particularly before and after entry into the trachea. This study highlighted the fitness costs of immunity and metabolism on the vector beetle, indicating the adaptation mechanisms and evolutionary trade-offs to PWN. [ABSTRACT FROM AUTHOR]

Populations may survive environmental deterioration by evolutionary adaptation. However, such evolutionary rescue events may be associated with ecological costs, such as reduction in growth performance and loss of ecologically important genetic diversity. Those negative ecological consequences may be mitigated by additional adaptive evolution. Both the ecological costs and the opportunities for additional evolution are contingent on the severity of environmental deterioration. Here, we hypothesize that populations evolutionarily rescued from faster, relative to slow, environmental deterioration suffer more severe long-term fitness decline and diversity loss. An experiment with the model adaptive radiation of bacterium Pseudomonas fluorescens exposed to abruptly or gradually increased antibiotic stress supported our hypothesis. The effect of additional adaptive evolution in recovering population size and ecological diversity was far from perfect. Cautions are therefore needed in predicting the role of rapid evolution for mitigating the impacts of environmental changes, in particular very fast environmental deterioration. We also found that bacterial populations rescued from gradually increased antibiotic stress evolved higher levels of antibiotic resistance, lending more support to aggressive chemotherapy in pathogen control. [ABSTRACT FROM AUTHOR]

To delay the resistance of pests to Bt cotton producing Cry1Ac, pyramided cotton has been planted to replace Cry1Ac-cotton. However, the resistance mechanism of insects to Cry2Ab is rarely researched. In this study, a Cry2Ab-resistant Helicoverpa armigera strain (96-2Ab60) was selected in laboratory, which had a resistance ratio of 778.84-fold compared to the 96S susceptible strain. Genetic analysis showed that the resistance of 96-2Ab60 strain was controlled by more than one locus, and inheritance mode was incompletely dominant. The Cry2Ab-resistant H. armigera had high cross-resistance to Cry1Ac (284.28-fold), Cry1Fa (282.50-fold), Cry1Aa (> 71.40-fold), Cry2Aa (30.14-fold) toxins, and low cross-resistance to Cry1Ab (9.94-fold) and Cry1Ca (> 8.05-fold), while it had no cross-resistance to abamectin and spinetoram and negative cross-resistance to Vip3Aa toxin (0.14-fold). The fitness costs of 96-2Ab60 resistant strain were evaluated on toxin-free artificial diet, compared with 96S strain, the life table parameters such as pupa survival rate, pupa weight, oviposition period, hatching rate of egg, r, and λ in 96-2Ab60 were significantly decreased, and total pre-oviposition and T were significantly increased. There were obvious fitness costs in 96-2Ab60 strain whose fitness value Rf (0.7341) was lower than that of the 96S strain. The larval mortalities of 96-2Ab60 and 96S fed on either DP33B (single-toxin cotton) or Bollgard II (pyramided cotton) were significantly higher than those fed on non-Bt cotton; however, the mortalities of 96-2Ab60 were obviously reduced compared with 96S. These results indicated that although these two Bt cottons could kill part of 96-2Ab60 larvae, 96-2Ab60 already had resistance to them. These results provide useful information to further understand Cry2Ab resistance mechanism and apply pyramided cotton for managing resistance in H. armigera. [ABSTRACT FROM AUTHOR]

The chemical application is considered one of the most crucial methods for controlling insect pests, especially in intensive farming practices. Owing to the chemical application, insect pests are exposed to toxic chemical insecticides along with other stress factors in the environment. Insects require energy and resources for survival and adaptation to cope with these conditions. Also, insects use behavioral, physiological, and genetic mechanisms to combat stressors, like new environments, which may include chemicals insecticides. Sometimes, the continuous selection pressure of insecticides is metabolically costly, which leads to resistance development through constitutive upregulation of detoxification genes and/or target-site mutations. These actions are costly and can potentially affect the biological traits, including development and reproduction parameters and other key variables that ultimately affect the overall fitness of insects. This review synthesizes published in-depth information on fitness costs induced by insecticide resistance in insect pests in the past decade. It thereby highlights the insecticides resistant to insect populations that might help design integrated pest management (IPM) programs for controlling the spread of resistant populations. [ABSTRACT FROM AUTHOR]

BACKGROUND: Helicoverpa zea, an economic pest in the south‐eastern United States, has evolved practical resistance to Bacillus thuringiensis (Bt) Cry toxins in maize and cotton. Insect resistance management (IRM) programs have historically required planting of structured non‐Bt maize, but because of its low adoption, the use of seed blends has been considered. To generate knowledge on target pest biology and ecology to help improve IRM strategies, nine field trials were conducted in 2019 and 2020 in Florida, Georgia, North Carolina, and South Carolina to evaluate the impact of Bt (Cry1Ab + Cry1F or Cry1Ab + Cry1F + Vip3A) and non‐Bt maize plants in blended and structured refuge treatments on H. zea pupal survival, weight, soil pupation depth, adult flight parameters, and adult time to eclosion. RESULTS: From a very large sample size and geography, we found a significant difference in pupal mortality and weight among treatments in seed blends with Vip3A, implying that cross‐pollination occurred between Bt and non‐Bt maize ears. There was no treatment effect for pupation depth, adult flight distance, and eclosion time. CONCLUSION: Results of this study demonstrate the potential impact of different refuge strategies on phenological development and survival of an important pest species of regulatory concern. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Despite increasing knowledge of the fitness costs of viability and fecundity involved in the herbicide-resistant weeds, relatively little is known about the linkage between herbicide resistance costs and phytochemical cues in weed species and biotypes. This study demonstrated relative fitness and phytochemical responses in six herbicide-resistant weeds and their susceptible counterparts. There were significant differences in the parameters of viability (growth and photosynthesis), fecundity fitness (flowering and seed biomass) and a ubiquitous phytochemical (–)-loliolide levels between herbicide-resistant weeds and their susceptible counterparts. Fitness costs occurred in herbicide-resistant Digitaria sanguinalis and Leptochloa chinensis but they were not observed in herbicide-resistant Alopecurus japonicas, Eleusine indica, Ammannia arenaria, and Echinochloa crus-galli. Correlation analysis indicated that the morphological characteristics of resistant and susceptible weeds were negatively correlated with (–)-loliolide concentration, but positively correlated with lipid peroxidation malondialdehyde and total phenol contents. Principal component analysis showed that the lower the (–)-loliolide concentration, the stronger the adaptability in E. crus-galli and E. indica. Therefore, not all herbicide-resistant weeds have fitness costs, but the findings showed several examples of resistance leading to improved fitness even in the absence of herbicides. In particular, (–)-loliolide may act as a phytochemical cue to explain the fitness cost of herbicide-resistant weeds by regulating vitality and fecundity. [ABSTRACT FROM AUTHOR]

Birds must contend with an array of anthropogenic threats during their migratory journeys. Many migrants are killed due to encounters with artificial light, introduced species, pollutants, and other anthropogenic hazards, while survivors of these encounters can suffer longer-lasting negative effects. The nonlethal effects of anthropogenic threats on migrating birds are less well understood than direct mortality, yet both potentially contribute to population declines. For example, building collisions frequently kill migrating birds, but the numbers of migrants that survive with an impaired ability to fly, refuel, or navigate to their destination on time is not well understood. Though not immediately fatal, such injuries can lead to delayed mortality and, ultimately, reduced lifetime reproductive success. Furthermore, migrants are likely to encounter multiple threats on their journeys, which can interact synergistically to further reduce fitness. For instance, light pollution attracts and disorients migrants, increasing the likelihood of window strikes, and surviving birds may be more vulnerable to predation from introduced predators. While considerable attention has focused on the lethal effects of anthropogenic threats, here, we review nonlethal effects of eight types of threats during migration, their interactions, and the pathways through which they can exert fitness costs. In doing so, we identify knowledge gaps and suggest areas for future research. In the absence of more information, we propose that the greatest reduction in the cumulative lethal and nonlethal impacts of anthropogenic hazards will be achieved by addressing threat types, like artificial light at night, that interact with and compound the impact of additional threats. Direct mortality from anthropogenic sources is recognized as a key driver of population declines, but a full understanding of the impacts of human activity on migrating birds must include the cumulative and interacting effects that extend beyond immediate mortality en route to influence overall migration success and lifetime fitness. [ABSTRACT FROM AUTHOR]

The chemical application is considered one of the most crucial methods for controlling insect pests, especially in intensive farming practices. Owing to the chemical application, insect pests are exposed to toxic chemical insecticides along with other stress factors in the environment. Insects require energy and resources for survival and adaptation to cope with these conditions. Also, insects use behavioral, physiological, and genetic mechanisms to combat stressors, like new environments, which may include chemicals insecticides. Sometimes, the continuous selection pressure of insecticides is metabolically costly, which leads to resistance development through constitutive upregulation of detoxification genes and/or target-site mutations. These actions are costly and can potentially affect the biological traits, including development and reproduction parameters and other key variables that ultimately affect the overall fitness of insects. This review synthesizes published in-depth information on fitness costs induced by insecticide resistance in insect pests in the past decade. It thereby highlights the insecticides resistant to insect populations that might help design integrated pest management (IPM) programs for controlling the spread of resistant populations.

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a major insect pest of rice in Asia and is mainly controlled with insecticides. Dinotefuran has been commercialized for control of N. lugens in China since 2013; however, the characteristics and mechanisms of resistance to dinotefuran are still unclear. Here, we conducted a long-term (from 2013 to 2021) and large geographical scale (11 provinces) resistance monitoring program for dinotefuran in the BPH in China. Before 2020, field populations of N. lugens have developed moderate resistance to dinotefuran, while since 2020, most field populations of N. lugens have developed high resistance. To develop a better resistance management strategy, a dinotefuran-resistant (Din-R) strain of N. lugens was selected in the laboratory to investigate the inheritance, possible mechanisms of resistance and potential fitness costs. This Din-R strain developed resistance to imidacloprid, nitenpyram and thiamethoxam. The dinotefuran resistance was controlled by multiple genes. RNA interference (RNAi)-mediated suppression of NlCYP6ER1, NlCYP6CS1 and NlCYP314A1 expression increased the susceptibility of N. lugens to dinotefuran. Transgenic lines of Drosophila melanogaster expressing NlCYP6ER1 or NlCYP314A1 were less susceptible to all four neonicotinoids. Furthermore, the Din-R strain had a relative fitness of 0.64 with a substantially decreased survival rate, emergence rate and fecundity. Collectively, our results showed that dinotefuran resistance was mediated by multiple CYP genes. The high expression of these genes was related to the cross-resistance of N. lugens to other neonicotinoids. This study provided valuable information for facilitating the development of neonicotinoids resistance management strategies. [ABSTRACT FROM AUTHOR]

Wolbachia is an endosymbiotic Alphaproteobacteria that can suppress insect-borne diseases through decreasing host virus transmission (population replacement) or through decreasing host population density (population suppression). We contrast natural Wolbachia infections in insect populations with Wolbachia transinfections in mosquitoes to gain insights into factors potentially affecting the long-term success of Wolbachia releases. Natural Wolbachia infections can spread rapidly, whereas the slow spread of transinfections is governed by deleterious effects on host fitness and demographic factors. Cytoplasmic incompatibility (CI) generated by Wolbachia is central to both population replacement and suppression programs, but CI in nature can be variable and evolve, as can Wolbachia fitness effects and virus blocking. Wolbachia spread is also influenced by environmental factors that decrease Wolbachia titer and reduce maternal Wolbachia transmission frequency. More information is needed on the interactions between Wolbachia and host nuclear/mitochondrial genomes, the interaction between invasion success and local ecological factors, and the long-term stability of Wolbachia-mediated virus blocking.

The brown planthopper, Nilaparvata lugens (Stål), is a major pest of rice crops, and its control is critical for food security. Pymetrozine has been recommended as an alternative to imidacloprid for controlling N. lugens, but the pest has developed high resistance to it, making its prohibition and restriction urgent. To address this issue, we conducted a study using a mixture of pymetrozine and zhongshengmycin with the effective ratio of 1:40, to evaluate the fitness costs in N. lugens. Our results showed that N. lugens had a relative fitness of 0.03 under this ratio, with significantly reduced longevity, female and male adult periods, total pre-oviposition days, and fecundity. Moreover, the expression levels of the uricase gene (EC1.7.3.3) and farnesyl diphosphate farnesyl transferase gene (EC2.5.1.21) were reduced in N. lugens. These genes are involved in urea metabolism and steroid biosynthesis pathway, respectively, and their suppression can interfere with the normal nutritional function of N. lugens. Our study demonstrates that the combination of chemical insecticides and antimicrobials can delay the development of resistance and improve the efficiency of pest control. This information is valuable for researchers developing management strategies to delay the development of pymetrozine resistance in N. lugens. [ABSTRACT FROM AUTHOR]

Helicoverpa zea (Boddie) is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis (Bt) maize and cotton in the United States. Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034. In this study, two tests (Test‐I and Test‐II) were conducted to evaluate the relative fitness of Bt‐susceptible and ‐resistant H. zea on non‐Bt diet (Test‐I and Test‐II) and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration (Test‐II only). Insect populations evaluated in Test‐I were two Bt‐susceptible strains and three Bt‐resistant strains (a single‐protein Cry1A.105‐, a single‐protein Cry2Ab2‐, and a dual‐protein Cry1A.105/Cry2Ab2‐resistant strains). Test‐II analyzed the same two susceptible strains, three backcrossed‐and‐reselected Cry1A.105/Cry2Ab2‐single‐/dual‐protein‐resistant strains, and three F1 heterozygous strains. Measurements of life table parameters showed that neither the single‐ nor dual‐protein Cry1A.105/Cry2Ab2 resistance in H. zea was associated with fitness costs under the test conditions. The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant, and the dual‐protein resistance was completely dominant. The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species. Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H. zea. [ABSTRACT FROM AUTHOR]

Drug rotation (cycling), in which multiple drugs are administrated alternatively, has the potential for limiting resistance evolution in pathogens. The frequency of drug alternation could be a major factor to determine the effectiveness of drug rotation. Drug rotation practices often have low frequency of drug alternation, with an expectation of resistance reversion. Here we, based on evolutionary rescue and compensatory evolution theories, suggest that fast drug rotation can limit resistance evolution in the first place. This is because fast drug rotation would give little time for the evolutionarily rescued populations to recover in population size and genetic diversity, and thus decrease the chance of future evolutionary rescue under alternate environmental stresses. We experimentally tested this hypothesis using the bacterium Pseudomonas fluorescens and two antibiotics (chloramphenicol and rifampin). Increasing drug rotation frequency reduced the chance of evolutionary rescue, and most of the finally surviving bacterial populations were resistant to both drugs. Drug resistance incurred significant fitness costs, which did not differ among the drug treatment histories. A link between population sizes during the early stages of drug treatment and the end‐point fates of populations (extinction vs survival) suggested that population size recovery and compensatory evolution before drug shift increase the chance of population survival. Our results therefore advocate fast drug rotation as a promising approach to reduce bacterial resistance evolution, which in particular could be a substitute for drug combination when the latter has safety risks. [ABSTRACT FROM AUTHOR]

As the pace of global warming accelerates, so do the threats to human health, urgent priority among them being antibiotic-resistant infections. In the context of global warming, this review summarises the direct and indirect effects of rising surface water temperatures on the development of bacterial antibiotic resistance. First, the resistance of typical pathogens such as E. coli increased with average temperature. This is not only related to increased bacterial growth rate and horizontal gene transfer frequency at high temperatures but also heat shock responses and cumulative effects. Secondly, the acceleration of bacterial growth indirectly promotes antibiotic residues in surface water, which is conducive to the growth and spread of resistant bacteria. Furthermore, the cascading effects of global warming, including the release of nutrients into the water and the resulting increase of bacteria and algae, indirectly promote the improvement of resistance. Water treatment processes exposed to high temperatures also increase the risk of resistance in surface water. The fitness costs of antibiotic resistance under these dynamic conditions are also discussed, concluding the relationship between various factors and resistance persistence. It was expected to provide a comprehensive basis for mitigating antibiotic resistance in the face of global warming. [Display omitted] [ABSTRACT FROM AUTHOR]

Emamectin benzoate is an avermectin bio-insecticide commonly used for managing several insect pests including Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a major polyphagous pest of many cultivated crops. The current study was conducted to evaluate the effects of emamectin benzoate on the fitness of S. litura populations exhibiting differential susceptibility to insecticide. The selection process and all the bioassays were carried out using 6-day-old 2nd instar larvae of S. litura. A field-collected population of S. litura was divided into two groups: one selected with emamectin benzoate for eight generations (EB-Sel) and the other kept unexposed (Unsel-Lab) to insecticide in the laboratory. An increase in resistance ratio from 1.71-fold in the F 1 generation to 22.54-fold in the F 8 generation of the EB-Sel population was observed compared to the Unsel-Lab (F 8) population. The EB-Sel and Unsel-Lab populations were treated with their respective lethal and sub-lethal concentrations which resulted in an extended development period, decreased larval survival, and adult emergence along with increased morphological abnormalities in adults. Significant reductions were observed in both male and female longevity, fecundity, egg hatching, net reproductive rate (R 0), intrinsic rate of increase (r m), and finite rate of increase (λ) in EB-Sel and Unsel-Lab populations. Higher concentrations of the insecticide also reduced the relative fitness (R f) of S. litura larvae, with maximum effect at LC 50 of the EB-Sel population where the R f value was 0.32 compared to the Unsel-Lab population. Both populations have been affected by emamectin benzoate exposure, however, the impact was more pronounced in the EB-Sel population indicating fitness costs. Our results suggested the fitness cost linked to emamectin benzoate resistance in S. litura which might favor managing insecticide resistance by reducing the frequency of resistant alleles by removing selection pressure. Consequently, our research provides significant insights to devise better pest management strategies for S. litura. [Display omitted] • Spodoptera litura was collected from fields and exposed to emamectin benzoate for eight generations. • The selection pressure increases resistance ratio in selected population to 22.54-fold compared to unselected population. • The insecticide exposure adversely impacted the life history traits of S. litura. • The relative fitness value of the selected strain was significantly low compared to unselected population. [ABSTRACT FROM AUTHOR]

The rate and accuracy of translation hinges upon multiple components – including transfer RNA (tRNA) pools, tRNA modifying enzymes, and rRNA molecules – many of which are redundant in terms of gene copy number or function. It has been hypothesized that the redundancy evolves under selection, driven by its impacts on growth rate. However, we lack empirical measurements of the fitness costs and benefits of redundancy, and we have poor a understanding of how this redundancy is organized across components. We manipulated redundancy in multiple translation components of Escherichia coli by deleting 28 tRNA genes, 3 tRNA modifying systems, and 4 rRNA operons in various combinations. We find that redundancy in tRNA pools is beneficial when nutrients are plentiful and costly under nutrient limitation. This nutrient-dependent cost of redundant tRNA genes stems from upper limits to translation capacity and growth rate, and therefore varies as a function of the maximum growth rate attainable in a given nutrient niche. The loss of redundancy in rRNA genes and tRNA modifying enzymes had similar nutrient-dependent fitness consequences. Importantly, these effects are also contingent upon interactions across translation components, indicating a layered hierarchy from copy number of tRNA and rRNA genes to their expression and downstream processing. Overall, our results indicate both positive and negative selection on redundancy in translation components, depending on a species’ evolutionary history with feasts and famines.

Helminths are common parasites of wild ungulates that can have substantial costs for growth, mortality and reproduction. Whilst these costs are relatively well documented for mature animals, knowledge of helminths' impacts on juveniles is more limited. Identifying these effects is important because young individuals are often heavily infected, and juvenile mortality is a key process regulating wild populations. Here, we investigated associations between helminth infection and overwinter survival in juvenile wild red deer (Cervus elaphus) on the Isle of Rum, Scotland. We collected fecal samples non-invasively from known individuals and used them to count propagules of 3 helminth taxa (strongyle nematodes, Fasciola hepatica and Elaphostrongylus cervi). Using generalized linear models, we investigated associations between parasite counts and overwinter survival for calves and yearlings. Strongyles were associated with reduced survival in both age classes, and F. hepatica was associated with reduced survival in yearlings, whilst E. cervi infection showed no association with survival in either age class. This study provides observational evidence for fitness costs of helminth infection in juveniles of a wild mammal, and suggests that these parasites could play a role in regulating population dynamics. [ABSTRACT FROM AUTHOR]

Abstract Sequestration, that is, the accumulation of plant toxins into body tissues for defense, was predicted to incur physiological costs and may require resistance traits different from those of non‐sequestering insects. Alternatively, sequestering species could experience a cost in the absence of toxins due to selection on physiological homeostasis under permanent exposure of sequestered toxins in body tissues. Milkweed bugs (Heteroptera: Lygaeinae) sequester high amounts of plant‐derived cardenolides. Although being potent inhibitors of the ubiquitous animal enzyme Na+/K+‐ATPase, milkweed bugs can tolerate cardenolides by means of resistant Na+/K+‐ATPases. Both adaptations, resistance and sequestration, are ancestral traits of the Lygaeinae. Using four milkweed bug species (Heteroptera: Lygaeidae: Lygaeinae) and the related European firebug (Heteroptera: Pyrrhocoridae: Pyrrhocoris apterus) showing different combinations of the traits “cardenolide resistance” and “cardenolide sequestration,” we tested how the two traits affect larval growth upon exposure to dietary cardenolides in an artificial diet system. While cardenolides impaired the growth of P. apterus nymphs neither possessing a resistant Na+/K+‐ATPase nor sequestering cardenolides, growth was not affected in the non‐sequestering milkweed bug Arocatus longiceps, which possesses a resistant Na+/K+‐ATPase. Remarkably, cardenolides increased growth in the sequestering dietary specialists Caenocoris nerii and Oncopeltus fasciatus but not in the sequestering dietary generalist Spilostethus pandurus, which all possess a resistant Na+/K+‐ATPase. We furthermore assessed the effect of dietary cardenolides on additional life history parameters, including developmental speed, longevity of adults, and reproductive success in O. fasciatus. Unexpectedly, nymphs under cardenolide exposure developed substantially faster and lived longer as adults. However, fecundity of adults was reduced when maintained on cardenolide‐containing diet for their entire lifetime but not when adults were transferred to non‐toxic sunflower seeds. We speculate that the resistant Na+/K+‐ATPase of milkweed bugs is selected for working optimally in a “toxic environment,” that is, when sequestered cardenolides are stored in the body.

Standard approaches to cultural evolution focus on the recipients or consumers. This does not take into account the fitness costs incurred in producing the behaviours or artefacts that become cultural, i.e. widespread in a social group. We argue that cultural evolution models should focus on these fitness costs and benefits of cultural production, particularly in the domain of ‘symbolic’ culture. In this approach, cultural products can be considered as a part of the extended phenotype of producers, which can affect the fitness of recipients in a positive way (through cooperation) but also in a detrimental way (through manipulation and exploitation). Taking the producers’ perspective may help explain the specific features of many kinds of cultural products.

Despite increasing knowledge of the fitness costs of viability and fecundity involved in the herbicide-resistant weeds, relatively little is known about the linkage between herbicide resistance costs and phytochemical cues in weed species and biotypes. This study demonstrated relative fitness and phytochemical responses in six herbicide-resistant weeds and their susceptible counterparts. There were significant differences in the parameters of viability (growth and photosynthesis), fecundity fitness (flowering and seed biomass) and a ubiquitous phytochemical (–)-loliolide levels between herbicide-resistant weeds and their susceptible counterparts. Fitness costs occurred in herbicide-resistant Digitaria sanguinalis and Leptochloa chinensis but they were not observed in herbicide-resistant Alopecurus japonicas, Eleusine indica, Ammannia arenaria, and Echinochloa crus-galli. Correlation analysis indicated that the morphological characteristics of resistant and susceptible weeds were negatively correlated with (–)-loliolide concentration, but positively correlated with lipid peroxidation malondialdehyde and total phenol contents. Principal component analysis showed that the lower the (–)-loliolide concentration, the stronger the adaptability in E. crus-galli and E. indica. Therefore, not all herbicide-resistant weeds have fitness costs, but the findings showed several examples of resistance leading to improved fitness even in the absence of herbicides. In particular, (–)-loliolide may act as a phytochemical cue to explain the fitness cost of herbicide-resistant weeds by regulating vitality and fecundity.

Simple Summary: This is the first study providing important time-specific, age-specific, and reproduction-specific data for managing Spodoptera frugiperda infestations in maize crops using chlorantraniliprole. The application of chlorantraniliprole insecticide suppressed the population of S. frugiperda. The results revealed that fecundity was affected by chlorantraniliprole in the second filial generation, which suggests that the insecticide application during spring will prevent S. frugiperda infestation in maize crops during the autumn season. Fall armyworm [Spodoptera frugiperda (J. E. Smith, 1797)] was first reported in the Americas, then spread to all the continents of the world. Chemical insecticides are frequently employed in managing fall armyworms. These insecticides have various modes of actions and target sites to kill the insects. Chlorantraniliprole is a selective insecticide with a novel mode of action and is used against Lepidopteran, Coleopteran, Isopteran, and Dipteran pests. This study determined chlorantraniliprole's lethal, sub-lethal, and trans-generational effects on two consecutive generations (F0, F1, and F2) of the fall armyworm. Bioassays revealed that chlorantraniliprole exhibited higher toxicity against fall armyworms with a LC50 of 2.781 mg/L after 48 h of exposure. Significant differences were noted in the biological parameters of fall armyworms in all generations. Sub-lethal concentrations of chlorantraniliprole showed prolonged larval and adult durations. The parameters related to the fitness cost in F0 and F1 generations showed non-significant differences. In contrast, the F2 generation showed lower fecundity at lethal (71 eggs/female) and sub-lethal (94 eggs/female) doses of chlorantraniliprole compared to the control (127.5–129.3 eggs/female). Age-stage specific survival rate (Sxj), life expectancy (Exj) and reproductive rate (Vxj) significantly differed among insecticide-treated groups in all generations compared to the control. A comparison of treated and untreated insects over generations indicated substantial differences in demographic parameters such as net reproduction rate (R0), intrinsic rate of increase (r), and mean generation time (T). Several biological and demographic parameters were shown to be negatively impacted by chlorantraniliprole. We conclude that chlorantraniliprole may be utilized to manage fall armyworms with lesser risks. [ABSTRACT FROM AUTHOR]

Acinetobacter baumannii is one of the main pathogens causing nosocomial and community-acquired infections. Tigecycline is an important antibiotic for the treatment of multidrug-resistant A. baumannii infections, but strains resistant to tigecycline have also emerged. There are still many unclear questions concerning the mechanism of tigecycline resistance in A. baumannii. In this study, tigecycline-susceptible and tigecycline-intermediate strains were gradually cultured with sub-minimum inhibitory concentrations of tigecycline to select for tigecycline-resistant mutants, and a tigecycline-resistant strain was cultured under 42 °C to select for tigecycline-susceptible mutants. We found that the acquisition of tigecycline resistance affected the susceptibility of the strains to other antibiotics. Resistance to ampicillin–sulbactam is negatively correlated with tigecycline resistance. The strains will experience fitness costs along with the acquisition of tigecycline resistance. Tigecycline resistance in the strains was not related to 16S rRNA target variation or outer membrane integrity alteration. By constructing a transposon mutation library, we found that transposon insertion of the adeL gene reduced the sensitivity of A. baumannii to tigecycline. This study provides important clues for understanding the mechanism of tigecycline resistance in A. baumannii. [ABSTRACT FROM AUTHOR]

In many taxa, individuals voluntarily detach a body part as a form to increase their chances of escaping predation. This defense mechanism, known as autotomy, has several consequences, such as changes in locomotor performance that may affect fitness. Scorpions of the genus Ananteris autotomize the "tail", which in fact corresponds to the last abdominal segments. After autotomy, individuals lose nearly 25% of their body mass and the last portion of the digestive tract, including the anus, which prevents defecation and leads to constipation, because regeneration does not occur. Here, we experimentally investigated the short‐ and long‐term effects of tail loss on the locomotor performance of Ananteris balzani. In a short‐term experiment, the maximum running speed (MRS) of males and females did not change after autotomy. Moreover, the relative mass of the lost tail did not affect the change in MRS after autotomy. In a long‐term experiment, autotomy had a negative effect on the MRS of males, but not of females. Autotomized over‐fed individuals suffered from severe constipation but were not slower than autotomized normally fed individuals. In conclusion, tail loss has no immediate effect on the locomotor performance of scorpions. The long‐term decrease in the locomotor performance of autotomized males may impair mate searching. However, because death by constipation takes several months, males have a long time to find mates and reproduce. Thus, the prolonged period between autotomy and death by constipation is crucial for understanding the evolution of one of the most extreme cases of autotomy in nature. [ABSTRACT FROM AUTHOR]

As a major crop pest, common cutworm (CCW) Spodoptera litura (Fabricius) has evolved resistance to several insecticides. Cyproflanilide is a novel meta -diamide insecticide targeting the γ-aminobutyric acid receptor (GABAR), and displays excellent insecticidal activity against lepidopteran pests, including CCW. Therefore, the resistance risk of CCW against cyproflanilide was assessed and the fitness cost was evaluated as well. After exposure with cyproflanilide for 10 generations (F10), the LC 50 values of CCW against cyproflanilide increased 1.26 - fold. When the realized heritability (h 2 ) to cyproflanilide in the field was assumed to be the laboratory-estimated value (h 2 = 0.09) and the mortality of CCW was 50–90 %, 126–57 generations were required to obtain a 10-fold resistance against cyproflanilide. After selected with cyproflanilide for 10 generations, the egg duration, larval duration, pre-pupal duration and female pupal weight were significantly increased, but the pupal duration, pupation rate and life-cycle rate were significantly decreased. The mean generation time (T) of F10 was significantly prolonged by 4.39 days. The value of relative fitness (R f) in F10 was 0.99. Although resistance developed slowly, the prolonged egg and larval durations have implications for managing CCW in the field. This information will contribute to identifying practices to delay the resistance development of CCW to cyproflanilide. [Display omitted] • Resistance against cyproflanilide developed slowly in the common cutworm. • Significantly prolonged durations of egg and larval in the Cyp-SEL (F10) strain were crucial for IPM. • Mean generation time (T) of the Cyp-SEL (F10) strain significantly prolonged by 4.39 days. [ABSTRACT FROM AUTHOR]

ABSTRACT The rapid emergence of phage-resistant bacterial mutants is a major challenge for phage therapy. Phage cocktails have been considered one approach to mitigate this issue. However, the synergistic effect of randomly selected phages in the cocktails is ambiguous. Here, we rationally designed a phage cocktail consisting of four phages that utilize the lipopolysaccharide (LPS) O antigen, the LPS outer core, the LPS inner core, and the outer membrane proteins BtuB and TolC on the Salmonella enterica serovar Enteritidis cell surface as receptors. We demonstrated that the four-phage cocktail could significantly delay the emergence of phage-resistant bacterial mutants compared to the single phage. To investigate the fitness costs associated with phage resistance, we characterized a total of 80 bacterial mutants resistant to a single phage or the four-phage cocktail. We observed that mutants resistant to the four-phage cocktail were more sensitive to several antibiotics than the single-phage-resistant mutants. In addition, all mutants resistant to the four-phage cocktail had significantly reduced virulence compared to wild-type strains. Our mouse model of Salmonella Enteritidis infection also indicated that the four-phage cocktail exhibited an enhanced therapeutic effect. Together, our work demonstrates an efficient strategy to design phage cocktails by combining phages with different bacterial receptors, which can steer the evolution of phage-resistant strains toward clinically exploitable phenotypes. IMPORTANCE The selection pressure of phage promotes bacterial mutation, which results in a fitness cost. Such fitness trade-offs are related to the host receptor of the phage; therefore, we can utilize knowledge of bacterial receptors used by phages as a criterion for designing phage cocktails. Here, we evaluated the efficacy of a phage cocktail made up of phages that target four different receptors on Salmonella Enteritidis through in vivo and in vitro experiments. Importantly, we found that pressure from phage cocktails with different receptors can drive phage-resistant bacterial mutants to evolve in a direction that entails more severe fitness costs, resulting in reduced virulence and increased susceptibility to antibiotics. These findings suggest that phage cocktail therapy using combinations of phages targeting different important receptors (e.g., LPS or the efflux pump AcrAB-TolC) on the host surface can steer the host bacteria toward more detrimental surface mutations than single-phage therapy, resulting in more favorable therapeutic outcomes.

Evidence of field-evolved resistance to emamectin benzoate has already been reported in Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in Brazil. To investigate the fitness costs associated with emamectin benzoate resistance, we used an F 2 screen to select resistant (Ben-R) and susceptible (Ben-S) strains of S. frugiperda from a field-collected population in Mato Grosso State, Brazil. Fitness costs were quantified by comparing biological (life history traits) and behavioral (ability to escape from predation by Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae)) parameters of Ben-R, Ben-S, and heterozygote strains reared on non-Bt maize and artificial diet. The resistance ratio of S. frugiperda resistance to emamectin benzoate was ∼ 2445-fold. Based on life table parameters, Ben-R and heterozygote strains had a higher mean generation time (T) than Ben-S strain on both food sources. The intrinsic rate of population increase (rm) of Ben-R strain was ∼ 35% lower than Ben-S and heterozygote strains. In contrast, there was no significant difference in predation rate of 3rd instar larvae of Ben-R, Ben-S and heterozygote strains by P. nigrispinus. Our findings suggest the presence of strong fitness costs associated with emamectin benzoate resistance in S. frugiperda , as evidenced by life history traits. Conversely, no fitness costs were linked to the defensive response against predation by P. nigrispinus. • Fitness costs of S. frugiperda resistant to emmamectin benzoate add insect resistance management. • Food source did not affect fitness costs. • Fitness costs of S. frugiperda is evident in life history traits. • No fitness costs were linked to predation by P. nigrispinus. [ABSTRACT FROM AUTHOR]

The cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) is a serious insect pest that infests legume crops. Flupyradifurone (FPF) is a butenolide insecticide that selectively targets sucking insects including aphids and whiteflies. However, the realized heritability (h 2 ) and fitness costs associated with resistance to FPF have not yet been assessed with A. craccivora. In this study, A. craccivora showed the potential to develop resistance to FPF under continuous selection, with an overall mean estimated h 2 of resistance of 0.21. Results of fitness costs showed no differences in the developmental time (except for N2 and N3), longevity, fecundity, adult pre-reproductive period (APRP), total pre-reproductive period (TPRP), and oviposition days (O d) of the FPF-R strain compared to the S-strain. In contrast, all population growth parameters, including the growth reproductive rate (GRR), net reproductive rate (R 0), intrinsic rate of increase (r), finite rate of increase (λ), mean generation time (T), and doubling time (DT), were significantly lower in the FPF-R strain than in the S-strain. Fitness cost studies revealed that resistance to FPF decreased the relative fitness of the FPF-R strain to 0.76 compared with that of the S-strain. The estimation of realized heritable h 2 and identification of resistance fitness costs provide a basis for designing insecticide resistance management (IRM) programs to sustain susceptibility in insect populations. • The Current work proved Aphis craccivora' potential to develop resistance to flupyradifurone. • The overall mean estimated h 2 of resistance strain was 0.21. • The resistant strain had a relative fitness of 0.76 [ABSTRACT FROM AUTHOR]

Afidopyropen, a newly identified chemical, is a derivative of pyripyropene A, which is produced by the filamentous fungus Penicillium coprobium. It is a promising novel pesticide applied against whiteflies in agriculture. In this study, the reversion and selection, cross-resistance patterns, synergistic effects, and fitness costs of afidopyropen resistance were studied in a field-developed resistant population of B. tabaci. Compared to a reference MED-S strain, the field-developed resistant Haidian (HD) population showed 36.5-fold resistance to afidopyropen. Significant reversion of resistance to afidopyropen was found in the HD population when it was kept with no selective pressure of the insecticide. The HD-Afi strain, developed from the HD population with afidopyropen pressure, developed 104.3-fold resistance to afidopyropen and significant cross-resistance to sulfoxaflor. Piperonyl butoxide (PBO) largely inhibited afidopyropen resistance in the HD-Afi strain, which indicates that P450 monooxygenase could be involved in the resistance. Significant fitness costs associated with afidopyropen resistance were observed in HD-Afi. This study indicates that a rotation of afidopyropen with other chemical control agents could be useful for impeding afidopyropen resistance in B. tabaci. In addition, we expanded upon the understanding of resistance to afidopyropen, offering evidence suggesting the importance of devising better strategies for the management of whiteflies. [ABSTRACT FROM AUTHOR]

The "high-dose/refuge" strategy is expected to work most effectively when resistance is inherited as a functionally recessive trait and the fitness costs associated with resistance are present. In the present study, a laboratory selected Mythimna separata strain that have evolved >634.5-fold resistance to Vip3Aa19 was used to determine the mode of inheritance. To determine if fitness costs were associated with the resistance, life history parameters (larva stage, pupa stage, pupal weight, adult longevity and fecundity) of resistant (RR), -susceptible (SS) and heterozygous (R♂S♀ and R♀S♂) strains on nontoxic diet were assayed. The LC50 values of R♀S♂ were significantly higher than that of R♂S♀ (254.58 μg/g vs. 14.75 μg/g), suggesting that maternal effects or sex linkage were present. The effective dominance h of F1 offspring decreased as concentration increased, suggesting the resistance was functionally dominant at low concentration and recessive at high concentration. The analysis of observed and expected mortality of the progeny from a backcross suggested that more than one locus is involved in conferring Vip3Aa19 resistance. The results showed that significant differences in many life history traits were observed among the four insect genotypes. In short, resistance to Vip3Aa19 in M. separata was inherited as maternal and multigene and the resistance in the strain was associated with significant fitness costs. The results described here provide useful information for understanding resistance evolution and for developing resistance management strategies. [ABSTRACT FROM AUTHOR]

Global warming, combined with an increasing influence of Atlantic Waters in the European Arctic, are causing a so-called Atlantification of the Arctic. This phenomenon is affecting the plankton biomass and communities with potential consequences for the upper trophic levels. Using long-term data (2005-2020) from a high Arctic zooplanktivorous seabird, the little auk (Alle alle), we tested the hypothesis that the Atlantification affects its diet, body condition and demography. We based our study on data collected in three fjords in West Spitsbergen, Svalbard, characterized by distinct oceanographic conditions. In all three fjords, we found a positive relationship between the inflow of Atlantic Waters and the proportion of Atlantic prey, notably of the copepod Calanus finmarchicus, in the little auk chick diet. A high proportion of Atlantic prey was negatively associated with adult body mass (though the effect size was small) and with chick survival (only in one fjord where chick survival until 21 days was available). We also found a negative and marginally significant effect of the average proportion of Atlantic prey in the chick diet on chick growth rate (data were available for one fjord only). Our results suggest that there are fitness costs for the little auk associated with the Atlantification of West Spitsbergen fjords. These costs seem especially pronounced during the late phase of the chick rearing period, when the energetic needs of the chicks are the highest. Consequently, even if little auks can partly adapt their foraging behaviour to changing environmental conditions, they are negatively affected by the ongoing changes in the Arctic marine ecosystems. These results stress the importance of long-term monitoring data in the Arctic to improve our understanding of the ongoing Atlantification and highlight the relevance of using seabirds as indicators of environmental change.

Lambda-cyhalothrin and bifenthrin from pyrethroids have been used for many years to control the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), which causes serious economic damage in many cultivated and ornamental plants worldwide. In this study, resistant populations previously selected in the laboratory with lambda cyhalothrin and bifenthrin (LR and BR, respectively) were compared with the susceptible strain GSS to assess the effect of the resistance on fitness. Life tables were created by using some biological parameters such as development time, fecundity and adult longevity. Data analysis revealed that lambda-cyhalothrin and bifenthrin resistant populations of T. urticae had no fitness disadvantages. The relative fitness values of the LR (1.09) and BR (1.19) populations also showed an advantage over the susceptible population. Total development and generation time were prolonged in both resistant populations. In the LR population, the life span of the adult females was prolonged, whereas the rm value was found to increase in the BR population. Total fecundity and egg hatchability were also found to be higher in both resistant populations than the susceptible strain GSS. The net reproduction rate (R0), one of the life table parameters, was significantly increased in the LR and BR populations. In this study, lambda-cyhalothrin and bifenthrin resistance affected some biological parameters in T.urticae, but the resistance did not produce a loss of fitness in the LR and BR populations. These findings have significant implications for resistance management strategies in terms of the state and management of resistance. [ABSTRACT FROM AUTHOR]

Interactions between the Anopheles mosquito vector and Plasmodium parasites shape how malaria is transmitted in endemic regions. The long association of these two organisms has led to evolutionary processes that minimize fitness costs of infection and benefit both players through shared nutrient resources, parasite immune suppression, and mosquito tolerance to infection. In this review we explore recent data describing how Plasmodium falciparum , the deadliest malaria parasite, associates with one of its most important natural mosquito hosts, Anopheles gambiae , and we discuss the implications of these findings for parasite transmission and vector control strategies currently in development. Parasites can exploit mosquito resources for their own development. Reproductive fitness costs are minimized in natural combinations of Plasmodium and Anopheles. A mating-induced tolerance mechanism has evolved in Anopheles gambiae to limit reproductive fitness costs of high-intensity Plasmodium infections. Nutrient resources within the mosquito can affect parasite development, sporozoite function, and infectivity. Manipulations to mosquito physiology have consequences for malaria transmission and proposed vector control strategies. [ABSTRACT FROM AUTHOR]

Insecticides are commonly utilized in agriculture and forestry for pest control, but their dispersal can pose hazards to humans and environment. Understanding resistance, inheritance patterns, and fitness costs can help manage resistance. A λ-cyhalothrin-resistant population (LCR) of Cydia pomonella , a global pest of pome fruits and walnuts, was obtained through selective insecticide breeding for 15 generations, showing stable moderate resistance (23.85-fold). This population was cross-resistant to deltamethrin (4.26-fold) but not to β-cypermethrin, chlorantraniliprole, chlorpyrifos, and avermectin. Genetic analysis revealed the resistance was autosomal, incompletely dominant, and controlled by multiple genes. Increased activity of glutathione S-transferases and cytochrome P450 monooxygenases (P450s) played a primary role in resistance, with specific genes up-regulated in LCR, and exhibited significant expression in midgut. LCR also exhibited fitness costs, including delays in development, reduced fecundity, and slower population growth. These findings contribute to understanding λ-cyhalothrin resistance in C. pomonella and can guide resistance management strategies.

Aphids (Hemiptera: Aphididae) maintain intimate relationships with a variety of symbiotic bacteria that can be important drivers of their evolutionary ecology. In addition to the obligate endosymbiont Buchnera aphidicola, aphids may harbor a series of facultative symbionts that can affect their physiology, as they may be involved in heat resistance, nutrition, reproduction and defense against parasitoids. Since the presence of facultative symbionts in aphids can be disadvantageous for parasitoids, it is hypothesized that these insects have developed strategies to adjust their responses to the presence of these bacteria. In this study, experiments were conducted to determine whether the presence of the facultative symbiont Serratia symbiotica in the pea aphid Acyrtosiphum pisum affects the development and the life-history traits of the generalist parasitoid Aphidius ervi (Hymenoptera: Braconidae). Behavioral assays were also performed to determine whether the infection status of host aphids influences the foraging behavior of the parasitoids. It was showed that the presence of S. symbiotica had negative effects on the development and the life-history traits of emerging parasitoids. It was found that parasitoids preferentially orient themselves to uninfected aphid hosts, probably through chemical clues, and that they adjust their foraging behavior by investing more time in patches composed of uninfected aphid hosts. In light of these results, it is assumed that the presence of S. symbiotica alters host aphid quality, which in turn influences the choice of the female parasitoids for oviposition as well as the quality of the emerging parasitoids. This study highlights the ability of parasitoid wasps to modify their perception and behavior towards aphids infected with facultative symbionts and how these microorganisms interfere with host-parasite relationships. [ABSTRACT FROM AUTHOR]

Sequestration, that is, the accumulation of plant toxins into body tissues for defense, was predicted to incur physiological costs and may require resistance traits different from those of non‐sequestering insects. Alternatively, sequestering species could experience a cost in the absence of toxins due to selection on physiological homeostasis under permanent exposure of sequestered toxins in body tissues. Milkweed bugs (Heteroptera: Lygaeinae) sequester high amounts of plant‐derived cardenolides. Although being potent inhibitors of the ubiquitous animal enzyme Na+/K+‐ATPase, milkweed bugs can tolerate cardenolides by means of resistant Na+/K+‐ATPases. Both adaptations, resistance and sequestration, are ancestral traits of the Lygaeinae. Using four milkweed bug species (Heteroptera: Lygaeidae: Lygaeinae) and the related European firebug (Heteroptera: Pyrrhocoridae: Pyrrhocoris apterus) showing different combinations of the traits "cardenolide resistance" and "cardenolide sequestration," we tested how the two traits affect larval growth upon exposure to dietary cardenolides in an artificial diet system. While cardenolides impaired the growth of P. apterus nymphs neither possessing a resistant Na+/K+‐ATPase nor sequestering cardenolides, growth was not affected in the non‐sequestering milkweed bug Arocatus longiceps, which possesses a resistant Na+/K+‐ATPase. Remarkably, cardenolides increased growth in the sequestering dietary specialists Caenocoris nerii and Oncopeltus fasciatus but not in the sequestering dietary generalist Spilostethus pandurus, which all possess a resistant Na+/K+‐ATPase. We furthermore assessed the effect of dietary cardenolides on additional life history parameters, including developmental speed, longevity of adults, and reproductive success in O. fasciatus. Unexpectedly, nymphs under cardenolide exposure developed substantially faster and lived longer as adults. However, fecundity of adults was reduced when maintained on cardenolide‐containing diet for their entire lifetime but not when adults were transferred to non‐toxic sunflower seeds. We speculate that the resistant Na+/K+‐ATPase of milkweed bugs is selected for working optimally in a "toxic environment," that is, when sequestered cardenolides are stored in the body. [ABSTRACT FROM AUTHOR]

BACKGROUND: Triflumezopyrim, a novel commercialized mesoionic chemical insecticide, has been confirmed as a promising insecticide for efficiently controlling the brown planthopper, Nilaparvata lugens (Stål). Here, a laboratory triflumezopyrim‐resistant (TR) strain and an isogenic susceptible (TS) strain were established to characterize the inheritance and fitness costs of triflumezopyrim resistance in N. lugens. RESULTS: After 29 generations of successive selection with triflumezopyrim, the TR strain developed a 155.23‐fold higher resistance level than the TS strain. The median lethal concentration (LC50) values from progenies (F1RS and F1SR) of reciprocal crosses between TR and TS strains suggested that triflumezopyrim resistance in N. lugens was autosomal and codominant. Chi‐square analyses of self‐bred and backcrossed progenies suggested that the resistance results from a polygenic effect. Compared to the TS strain, the TR strain showed a lower relative fitness (0.62) with a significantly decreased female adult period, longevity, total fecundity, egg hatchability, intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and prolonged pre‐adult period and total preoviposition period (TPOP). CONCLUSION: The inheritance mode of triflumezopyrim resistance in N. lugens was characterized as autosomal, codominant and polygenic. The resistance had a fitness cost, which may be an important factor limiting the evolution of resistance. These findings provide valuable information for optimizing resistance management strategies to delay triflumezopyrim resistance development and maintain sustainable control of N. lugens. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Many mammals grow up with siblings, and interactions between them can influence offspring phenotype and fitness. Among these interactions, sibling competition between different‐age offspring should lead to reproductive and survival costs on the younger sibling, while sibling cooperation should improve younger sibling's reproductive potential and survival. However, little is known about the consequences of sibling effects on younger offspring life‐history trajectory, especially in long‐lived mammals.We take advantage of a large, multigenerational demographic dataset from semi‐captive Asian elephants to investigate how the presence and sex of elder siblings influence the sex, survival until 5 years old, body condition, reproductive success (i.e. age at first reproduction and lifetime reproductive success) and long‐term survival of subsequent offspring.We find that elder siblings have heterogeneous effects on subsequent offspring life‐history traits depending on their presence, their sex and the sex of the subsequent offspring (named focal calf).Overall, the presence of an elder sibling (either sex) strongly increased focal calf long‐term survival (either sex) compared to sibling absence. However, elder sisters had higher impact on the focal sibling than elder brothers. Focal females born after a female display higher long‐term survival, and decreased age at first reproduction when raised together with an elder sister rather than a brother. Focal males born after a female rather than a male showed lower survival but higher body weight when both were raised together. We did not detect any sibling effects on the sex of the focal calf sex, survival until 5 years old and lifetime reproductive success.Our results highlight the general complexity of sibling effects, but broadly that elder siblings can influence the life‐history trajectory of subsequent offspring. We also stress the importance of considering all life stages when evaluating sibling effects on life trajectories. [ABSTRACT FROM AUTHOR]

ABSTRACT The emergence of the plasmid-mediated colistin resistance gene mcr-1 and the plasmid-mediated tigecycline resistance gene tet(X4) represents a significant threat to public health. Although mcr-1 and tet(X4) have been reported to coexist in the same isolate, there are no reports on the emergence of plasmids coharboring mcr-1 and tet(X4). In this study, we aimed to investigate the opportunities for the emergence of mcr-1- and tet(X4)-coharboring plasmids and their destiny in Escherichia coli. Two plasmids carrying both mcr-1 and tet(X4) were constructed through conjugation assays and confirmed by S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Nanopore long-read sequencing. Seven evolved plasmids carrying mcr-1 and tet(X4) from one of the two plasmids were acquired after continuous evolutionary processes. The fitness effects of mcr-1- and tet(X4)-coharboring plasmids were studied by stability experiments, competition experiments, and growth curve measurements. A plasmid carrying mcr-1 and tet(X4) and conferring no fitness cost to its host strain E. coli C600 emerged after evolution during serial passages of bacteria. We proved that it can be anticipated that mcr-1 and tet(X4) could appear in a single plasmid, and the possibility of occurrence in field strains should be monitored constantly. The originally formed cointegrate plasmids coharboring mcr-1 and tet(X4) could evolve into a plasmid with lower fitness costs. This will undoubtedly accelerate the transmission of mcr-1 and tet(X4) globally. The findings highlighted the great possibility of novel hybrid plasmids positive for mcr-1 and tet(X4), and the risk is worthy of increasing attention and public concern globally. IMPORTANCE Tigecycline and colistin are used as last-resort therapies to treat infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, the emergence of the plasmid-mediated tigecycline resistance gene tet(X4) and the plasmid-mediated colistin resistance gene mcr-1 represents a significant threat to human health. A plasmid coharboring mcr-1 and tet(X4) has not emerged so far, but the potential risk should not be ignored. Plasmids coharboring such vital resistance genes will greatly accelerate the progression of pan-drug resistance among pathogens globally. Therefore, evaluation of the emerging opportunity for the mcr-1- and tet(X4)-coharboring plasmids and their destiny in E. coli is of great significance. We provide important insight into the contributions of intI1, IS26, a truncated ISCR2 (ΔISCR2), and IS4321R during the generation of cointegrate plasmids carrying mcr-1 and tet(X4) and highlight the importance of antimicrobials in the evolution and diversity of mcr-1- and tet(X4)-coharboring plasmids. We show that monitoring of the occurrence of mcr-1-carrying MDR plasmids and tet(X4)-bearing MDR plasmids in the same strain should be strengthened to avoid the formation of mcr-1- and tet(X4)-coharboring plasmids.