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The BA.2 sublineage of the SARS-CoV-2 Omicron variant has become dominant in most countries around the world; however, the prevalence of BA.4 and BA.5 is increasing rapidly in several regions. BA.2 is less pathogenic in animal models than previously circulating variants of concern 1-4 . Compared with BA.2, however, BA.4 and BA.5 possess additional substitutions in the spike protein, which play a key role in viral entry, raising concerns that the replication capacity and pathogenicity of BA.4 and BA.5 are higher than those of BA.2. Here we have evaluated the replicative ability and pathogenicity of BA.4 and BA.5 isolates in wild-type Syrian hamsters, human ACE2 (hACE2) transgenic hamsters and hACE2 transgenic mice. We have observed no obvious differences among BA.2, BA.4 and BA.5 isolates in growth ability or pathogenicity in rodent models, and less pathogenicity compared to a previously circulating Delta (B.1.617.2 lineage) isolate. In addition, in vivo competition experiments revealed that BA.5 outcompeted BA.2 in hamsters, whereas BA.4 and BA.2 exhibited similar fitness. These findings suggest that BA.4 and BA.5 clinical isolates have similar pathogenicity to BA.2 in rodents and that BA.5 possesses viral fitness superior to that of BA.2., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Widespread insecticide resistance in African malaria vectors raises concerns over the potential to compromise malaria vector control interventions. Understanding the evolution of resistance mechanisms, and whether the selective disadvantages are large enough to be useful in resistance management or designing suitable control strategies is crucial. This study assessed whether insecticide resistance to pyrethroids has an effect on the gonotrophic cycle and reproductive potential of malaria vector Anopheles gambiae. Comparative tests were performed with pyrethroid-resistant and susceptible colonies of Anopheles gambiae colonized from the same geographical area, and the reference Kisumu strain was used as a control. Adult females aged 3 days old were given a blood meal and kept separately for individual egg-laying. The number of days taken to lay eggs post-blood-feeding was recorded to determine the length of the gonotrophic cycle. To measure adult longevity and reproduction potential, newly emerged males and females of equal numbers were aspirated into a cage and females allowed to blood feed daily. The number of eggs laid and the surviving mosquitoes were recorded daily to determine fecundity, net reproduction rate, intrinsic growth rate and adult longevity. Overall, the resistant females had a significantly longer (1.8 days) gonotrophic cycle than susceptible females (F 2, 13  = 9. 836, P < 0.01). The proportion of resistant females that laid eggs was lower 31.30% (94/300) compared to 54% (162/300) in the susceptible colony and 65.7% (197/300) in the Kisumu strain. The mean number of eggs laid per female was significantly lower in the resistant colony (88.02 ± 20) compared to the susceptible colony (104.9 ± .28.8) and the Kisumu strain (97.6 ± 34.8). The adult longevity was significantly higher for resistant (39.7 ± 1.6 days) compared to susceptible (29.9 ± 1.7 days) and the Kisumu strain was (29.6 ± 1.1 days) (F 2,8  = 45.05, P < 0.0001). Resistant colony exhibited a lower fecundity (4.3 eggs/females/day) and net reproductive rate (2.6 offsprings/female/generation) compared to the susceptible colony (8.6 eggs/female/day; 4.7 offsprings/female/generation respectively) and Kisumu strain (9.7 eggs/female/day; 4.1 offsprings/female/generation respectively). The study suggests high fitness cost on reproductive parameters of pyrethroid-resistant mosquitoes particularly on the duration of gonotrophic cycle, fecundity and net reproductive rate. These fitness costs are likely associated with maintaining both target site and metabolic mechanisms of resistance to pyrethroids. Despite these costs, resistant mosquitoes had longer longevity. These results give insights to understanding the fitness cost of insecticide resistance and thus are critical when predicting the epidemiological impact of insecticide resistance., (© 2022. The Author(s).)

Lévy flight is a type of random walk that characterizes the behaviour of many natural phenomena studied across a multiplicity of academic disciplines; within biology specifically, the behaviour of fish, birds, insects, mollusks, bacteria, plants, slime molds, t-cells, and human populations. The Lévy flight foraging hypothesis states that because Lévy flights can maximize an organism's search efficiency, natural selection should result in Lévy-like behaviour. Empirical and theoretical research has provided ample evidence of Lévy walks in both extinct and extant species, and its efficiency across models with a diversity of resource distributions. However, no model has addressed the maintenance of Lévy flight foraging through evolutionary processes, and existing models lack ecological breadth. We use numerical simulations, including lineage-based models of evolution with a distribution of move lengths as a variable and heritable trait, to test the Lévy flight foraging hypothesis. We include biological and ecological contexts such as population size, searching costs, lifespan, resource distribution, speed, and consider both energy accumulated at the end of a lifespan and averaged over a lifespan. We demonstrate that selection often results in Lévy-like behaviour, although conditional; smaller populations, longer searches, and low searching costs increase the fitness of Lévy-like behaviour relative to Brownian behaviour. Interestingly, our results also evidence a bet-hedging strategy; Lévy-like behaviour reduces fitness variance, thus maximizing geometric mean fitness over multiple generations., Competing Interests: The authors have declared that no competing interests exist.

The mechanisms and consequences of genome evolution on viral fitness following host shifts are poorly understood. In addition, viral fitness -the ability of an organism to reproduce and survive- is multifactorial and thus difficult to quantify. Influenza A viruses (IAVs) circulate broadly among wild birds and have jumped into and become endemic in multiple mammalian hosts, including humans, pigs, dogs, seals, and horses. H3N8 equine influenza virus (EIV) is an endemic virus of horses that originated in birds and has been circulating uninterruptedly in equine populations since the early 1960s. Here, we used EIV to quantify changes in infection phenotype associated to viral fitness due to genome-wide changes acquired during long-term adaptation. We performed experimental infections of two mammalian cell lines and equine tracheal explants using the earliest H3N8 EIV isolated (A/equine/Uruguay/63 [EIV/63]), and A/equine/Ohio/2003 (EIV/2003), a monophyletic descendant of EIV/63 isolated 40 years after the emergence of H3N8 EIV. We show that EIV/2003 exhibits increased resistance to interferon, enhanced viral replication, and a more efficient cell-to-cell spread in cells and tissues. Transcriptomics analyses revealed virus-specific responses to each virus, mainly affecting host immunity and inflammation. Image analyses of infected equine respiratory explants showed that despite replicating at higher levels and spreading over larger areas of the respiratory epithelium, EIV/2003 induced milder lesions compared to EIV/63, suggesting that adaptation led to reduced tissue pathogenicity. Our results reveal previously unknown links between virus genotype and the host response to infection, providing new insights on the relationship between virus evolution and fitness., Competing Interests: The authors have declared that no competing interests exist.

Seed germination is critical for plant survival and agricultural production, which is affected by both internal seed factors and external environmental conditions. However, the genetic basis and underlying molecular mechanisms of early seed germination in crops remain largely unclear. Here, we report that R2R3 MYB transcription factor Carbon Starved Anther (CSA) is expressed specifically in Oryza sativa embryo and aleurone in response to seed imbibition, peaking at 3-6 h and undetectable by 24-h post-imbibition. CSA seeds germinated more quickly than wild-type rice seeds and had higher levels of amylase activity, glucose, and inactive abscisic acid-glucose ester (ABA-GE), but lower levels of ABA. Through analyzing the CSA-associated transcriptome and CSA binding to downstream target genes, we identified two glycolytic genes as direct CSA targets. CSA inhibits Amylase 3A expression to limit glucose production from starch and activates Os3BGlu6 expression to promote de-conjugation of ABA-GE to ABA; these functions serve to slow germination and improve seedling resilience to abiotic stress in the first 3 weeks of growth. Therefore, this study unveils a protection mechanism conferred by CSA during early seed germination by balancing glucose and ABA metabolism to optimize seed germination and stress response fitness., (© American Society of Plant Biologists 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Associated microorganisms ("microbiota") play a central role in determining many animals' survival and reproduction characteristics. The impact of these microbial influences on an animal's fitness, or population growth, in a given environment has not been defined as clearly. We focused on microbiota-dependent host fitness by measuring life span and fecundity in Drosophila melanogaster fruit flies reared individually with 14 different bacterial species. Consistent with previous observations, the different bacteria significantly influenced the timing of fly life span and fecundity. Using Leslie matrices, we show that fly fitness was lowest when the microbes caused the flies to invest in life span over fecundity. Computational permutations showed that the positive fitness effect of investing in reproduction was reversed if fly survival over time was low, indicating that the observed fitness influences of the microbes could be context dependent. Finally, we showed that fly fitness is not influenced by bacterial genes that shape fly life span or fly triglyceride content, a trait that is related to fly survival and reproduction. Also, metagenome-wide association did not identify any microbial genes that were associated with variation in fly fitness. Therefore, the bacterial genetic basis for influencing fly fitness remains unknown. We conclude that bacteria influence a fly's reproductive timing more than total reproductive output and that (e.g., environmental) conditions that influence fly survival likely determine which bacteria benefit fly fitness. IMPORTANCE The ability of associated microorganisms ("microbiota") to influence animal life history traits has been recognized and investigated, especially in the past 2 decades. For many microbial communities, there is not always a clear definition of whether the microbiota or its members are beneficial, pathogenic, or relatively neutral to their hosts' fitness. In this study, we report the influence of individual members of the microbiota on Drosophila melanogaster fitness using Leslie matrices that combine the microbial influences on fly survival and reproduction into a single fitness measure. Our results are consistent with a previous report that, in the laboratory, acetic acid bacteria are more beneficial to the flies than many strains of lactic acid bacteria. We add to the previous finding by showing that this benefit depends on fly survival rate. Together, our work helps to show how the microbiota of a fly influences its laboratory fitness and how these effects may translate to a wild setting.

Studies have explored the assisted reproductive technology (ART) outcomes of Y-chromosome azoospermia factor c (AZFc) microdeletions, but the effect of sperm source on intracytoplasmic sperm injection (ICSI) remains unknown. To determine the ART results of ICSI using testicular sperm and ejaculated sperm from males with AZFc microdeletions, we searched Embase, Web of Science, and PubMed to conduct a systematic review and meta-analysis. The first meta-analysis results for 106 cycles in five studies showed no significant differences in the live birth rate between the testicular sperm group and the ejaculated sperm group (risk ratio: 0.97, 95% confidence interval [CI]: 0.73-1.28, P = 0.82). The second meta-analysis of 106 cycles in five studies showed no difference in the abortion rate between the testicular sperm group and ejaculated sperm group (risk ratio: 1.06, 95% CI: 0.54-2.06, P = 0.87). The third meta-analysis of 386 cycles in seven studies showed no significant difference in clinical pregnancy rates between the testicular sperm group and the ejaculated sperm group (risk ratio: 1.24, 95% CI: 0.66-2.34, P = 0.50). Inevitable heterogeneity weakened our results. However, our results indicated that testicular sperm and ejaculated sperm yield similar ART outcomes, representing a meaningful result for clinical treatment. More properly designed studies are needed to further confirm our conclusions., Competing Interests: None

A small number of pluripotent cells within early embryo gives rise to all cells in the adult body, including germ cells. Hence, any mutations occurring in the pluripotent cell population are at risk of being propagated to their daughter cells and could lead to congenital defects or embryonic lethality and pose a risk of being transmitted to future generations. The observation that genetic errors are relatively common in preimplantation embryos, but their levels reduce as development progresses, suggests the existence of mechanisms for clearance of aberrant, unfit or damaged cells. Although early human embryogenesis is largely experimentally inaccessible, pluripotent stem cell (PSC) lines can be derived either from the inner cell mass (ICM) of a blastocyst or by reprogramming somatic cells into an embryonic stem cell-like state. PSCs retain the ability to differentiate into any cell type in vitro and, hence, they represent a unique and powerful tool for studying otherwise intractable stages of human development. The advent of PSCs has also opened up a possibility of developing regenerative medicine therapies, either through PSC differentiation in vitro or by creating interspecies chimeras for organ replacement. Here, we discuss the emerging evidence of cell selection in human PSC populations in vivo and in vitro and we highlight the implications of understanding this phenomenon for human development and regenerative medicine., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Environmental fitness is an essential component of animal survival. Fitness is achieved through responsive physiological plasticity of tissues across the entire body, and particularly in the nervous system. At the molecular level, neural plasticity is mediated via gene-environmental interactions whereby developmental cues and experience dependent input adapt neuronal function to ever changing demands. To this end, neuronal gene regulation must be coupled to changes in neural activity. Seminal discoveries of the 20th century demonstrated neural activity modifies gene expression through calcium-dependent gene transcription. Building on this model, recent work over the last two decades shows that mRNA products of transcriptional programming continue to be regulated in the neuron through the activity-dependent post-transcriptional action of microRNAs (miRNAs). miRNAs are special post-transcriptional regulators that can tune gene expression within the spatial and temporal requirements of synaptic compartments. This mode of gene regulation has proven to be essential for synaptic function and plasticity as miRNA loss of function is highly associated with neural disease. In this review we will discuss current perspective on the link between presynaptic plasticity and miRNA biogenesis in the neuron.

Variation in body size has important implications for physical performance and fitness. For insects, adult size and morphology are determined by larval growth and metamorphosis. Female blue orchard bees, Osmia lignaria, (Say) provision a finite quantity of food to their offspring. In this study, we asked how provision-dependent variation in size changes adult morphology. We performed a diet manipulation in which some larvae were starved in the final instar and some were given unlimited food. We examined the consequences on adult morphology in two ways. First, allometric relationships between major body regions (head, thorax, abdomen) and total body mass were measured to determine relative growth of these structures. Second, morphometrics that are critical for flight (wing area, wing loading, and extra flight power index) were quantified. Head and thorax mass had hyperallometric relationships with body size, indicating these parts become disproportionately large in adults when larvae are given copious provisions. However, abdominal mass and wing area increased hypoallometrically with body size. Thus, large adults had disproportionately lighter abdomens and smaller wing areas than smaller adults. Though both males and females followed these general patterns, allometric patterns were affected by sex. For flight metrics, small adults had reduced wing loading and an increased extra flight power index. These results suggest that diet quantity alters development in ways that affect the morphometric trait relationships in adult O. lignaria and may lead to functional differences in performance., (© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America.)

Klebsiella pneumoniae (Kp) is an important cause of healthcare-associated infections, which increases patient morbidity, mortality, and hospitalization costs. Gut colonization by Kp is consistently associated with subsequent Kp disease, and patients are predominantly infected with their colonizing strain. Our previous comparative genomics study, between disease-causing and asymptomatically colonizing Kp isolates, identified a plasmid-encoded tellurite (TeO3-2)-resistance (ter) operon as strongly associated with infection. However, TeO3-2 is extremely rare and toxic to humans. Thus, we used a multidisciplinary approach to determine the biological link between ter and Kp infection. First, we used a genomic and bioinformatic approach to extensively characterize Kp plasmids encoding the ter locus. These plasmids displayed substantial variation in plasmid incompatibility type and gene content. Moreover, the ter operon was genetically independent of other plasmid-encoded virulence and antibiotic resistance loci, both in our original patient cohort and in a large set (n = 88) of publicly available ter operon-encoding Kp plasmids, indicating that the ter operon is likely playing a direct, but yet undescribed role in Kp disease. Next, we employed multiple mouse models of infection and colonization to show that 1) the ter operon is dispensable during bacteremia, 2) the ter operon enhances fitness in the gut, 3) this phenotype is dependent on the colony of origin of mice, and 4) antibiotic disruption of the gut microbiota eliminates the requirement for ter. Furthermore, using 16S rRNA gene sequencing, we show that the ter operon enhances Kp fitness in the gut in the presence of specific indigenous microbiota, including those predicted to produce short chain fatty acids. Finally, administration of exogenous short-chain fatty acids in our mouse model of colonization was sufficient to reduce fitness of a ter mutant. These findings indicate that the ter operon, strongly associated with human infection, encodes factors that resist stress induced by the indigenous gut microbiota during colonization. This work represents a substantial advancement in our molecular understanding of Kp pathogenesis and gut colonization, directly relevant to Kp disease in healthcare settings., Competing Interests: The authors have declared that no competing interests exist.

Long-term survival of bacterial pathogens during persistent bacterial infections can be associated with antibiotic treatment failure and poses a serious public health problem. Infections caused by the Gram-negative pathogen Pseudomonas aeruginosa, which can cause both acute and chronic infections, are particularly challenging due to its high intrinsic resistance to antibiotics. The ineffectiveness of antibiotics is exacerbated when bacteria reside intracellularly within host cells where they can adopt a drug tolerant state. While the early steps of adherence and entry of P. aeruginosa into mammalian cells have been described, the subsequent fate of internalized bacteria, as well as host and bacterial molecular pathways facilitating bacterial long-term survival, are not well defined. In particular, long-term survival within bladder epithelial cells has not been demonstrated and this may have important implications for the understanding and treatment of UTIs caused by P. aeruginosa. Here, we demonstrate and characterize the intracellular survival of wild type (WT) P. aeruginosa inside bladder epithelial cells and a mutant with a disruption in the bacterial two-component regulator AlgR that is unable to survive intracellularly. Using simultaneous dual RNA-seq transcriptional profiling, we define the transcriptional response of intracellular bacteria and their corresponding invaded host cells. The bacterial transcriptional response demonstrates that WT bacteria rapidly adapt to the stress encountered in the intracellular environment in contrast to ΔalgR bacteria. Analysis of the host transcriptional response to invasion suggests that the NF-κB signaling pathway, previously shown to be required for extracellular bacterial clearance, is paradoxically also required for intracellular bacterial survival. Lastly, we demonstrate that intracellular survival is important for pathogenesis of P. aeruginosa in vivo using a model of murine urinary tract infection. We propose that the unappreciated ability of P. aeruginosa to survive intracellularly may play an important role in contributing to the chronicity and recurrence of P. aeruginosa in urinary tract infections., Competing Interests: The authors have declared that no competing interests exist.

The Peptidoglycan (PG) cell wall of the Lyme disease (LD) spirochete, Borrelia burgdorferi (Bb), contributes to structural and morphological integrity of Bb; is a persistent antigen in LD patients; and has a unique pentapeptide with L-Ornithine as the third amino acid that cross-links its glycan polymers. A borrelial homolog (BB&#95;0167) interacted specifically with borrelilal PG via its peptidoglycan interacting motif (MHELSEKRARAIGNYL); was localized to the protoplasmic cylinder of Bb; and was designated as Borrelia peptidoglycan interacting Protein (BpiP). A bpiP mutant displayed no defect under in vitro growth conditions with similar levels of several virulence-related proteins. However, the burden of bpiP mutant in C3H/HeN mice at day 14, 28 and 62 post-infection was significantly lower compared to control strains. No viable bpiP mutant was re-isolated from any tissues at day 62 post-infection although bpiP mutant was able to colonize immunodeficient SCID at day 28 post-infection. Acquisition or transmission of bpiP mutant by Ixodes scapularis larvae or nymphs respectively, from and to mice, was significantly lower compared to control strains. Further analysis of bpiP mutant revealed increased sensitivity to vancomycin, osmotic stress, lysosomal extracts, human antimicrobial peptide cathelicidin-LL37, complement-dependent killing in the presence of day 14 post-infection mouse serum and increased internalization of CFSC-labeled bpiP mutant by macrophages and dendritic cells compared to control strains. These studies demonstrate the importance of accessory protein/s involved in sustaining integrity of PG and cell envelope during different phases of Bb infection., Competing Interests: The authors have declared that no competing interests exist.

Hypervirulent K. pneumoniae (hvKp) is a distinct pathotype that causes invasive community-acquired infections in healthy individuals. Hypermucoviscosity (hmv) is a major phenotype associated with hvKp characterized by copious capsule production and poor sedimentation. Dissecting the individual functions of CPS production and hmv in hvKp has been hindered by the conflation of these two properties. Although hmv requires capsular polysaccharide (CPS) biosynthesis, other cellular factors may also be required and some fitness phenotypes ascribed to CPS may be distinctly attributed to hmv. To address this challenge, we systematically identified genes that impact capsule and hmv. We generated a condensed, ordered transposon library in hypervirulent strain KPPR1, then evaluated the CPS production and hmv phenotypes of the 3,733 transposon mutants, representing 72% of all open reading frames in the genome. We employed forward and reverse genetic screens to evaluate effects of novel and known genes on CPS biosynthesis and hmv. These screens expand our understanding of core genes that coordinate CPS biosynthesis and hmv, as well as identify central metabolism genes that distinctly impact CPS biosynthesis or hmv, specifically those related to purine metabolism, pyruvate metabolism and the TCA cycle. Six representative mutants, with varying effect on CPS biosynthesis and hmv, were evaluated for their impact on CPS thickness, serum resistance, host cell association, and fitness in a murine model of disseminating pneumonia. Altogether, these data demonstrate that hmv requires both CPS biosynthesis and other cellular factors, and that hmv and CPS may serve distinct functions during pathogenesis. The integration of hmv and CPS to the metabolic status of the cell suggests that hvKp may require certain nutrients to specifically cause deep tissue infections., Competing Interests: The authors have declared that no competing interests exist.

Several phenotypes that impact the capacity of cancer cells to survive and proliferate are dynamic. Here we used the number of cells in colonies as an assessment of fitness and devised a novel method called Dynamic Fitness Analysis (DynaFit) to measure the dynamics in fitness over the course of colony formation. DynaFit is based on the variance in growth rate of a population of founder cells compared with the variance in growth rate of colonies with different sizes. DynaFit revealed that cell fitness in cancer cell lines, primary cancer cells, and fibroblasts under unhindered growth conditions is dynamic. Key cellular mechanisms such as ERK signaling and cell-cycle synchronization differed significantly among cells in colonies after 2 to 4 generations and became indistinguishable from randomly sampled cells regarding these features. In the presence of cytotoxic agents, colonies reduced their variance in growth rate when compared with their founder cell, indicating a dynamic nature in the capacity to survive and proliferate in the presence of a drug. This finding was supported by measurable differences in DNA damage and induction of senescence among cells of colonies. The presence of epigenetic modulators during the formation of colonies stabilized their fitness for at least four generations. Collectively, these results support the understanding that cancer cell fitness is dynamic and its modulation is a fundamental aspect to be considered in comprehending cancer cell biology and its response to therapeutic interventions. SIGNIFICANCE: Cancer cell fitness is dynamic over the course of the formation of colonies. This dynamic behavior is mediated by asymmetric mitosis, ERK activity, cell-cycle duration, and DNA repair capacity in the absence or presence of a drug., (©2020 American Association for Cancer Research.)

Migration may expose individuals to a wide range of increasing anthropogenic threats. In addition to direct mortality effects, this exposure may influence post-migratory reproductive fitness. Partial migration-where a population comprises migrants and residents-represents a powerful opportunity to explore carryover effects of migration. Studies of partial migration in birds typically examine short-distance systems; here we studied an unusual system where residents breed in mixed colonies alongside long-distance trans-Saharan migrants (lesser kestrels (Falco naumanni) in Spain). Combining geolocator data, stable isotope analysis and resighting data, we examined the effects of this stark difference in migratory strategy on body condition, breeding phenology and breeding success. We monitored four colonies in two regions of southern Spain for five consecutive years (2014-2018), yielding 1962 captures, determining migratory strategy for 141 adult bird-years. Despite a 3000-km difference in distance travelled, we find no effect of strategy on breeding parameters. We find weak evidence for a short-term negative carryover effect of migration on body condition, but this was only apparent in the breeding region with lower primary productivity. Our results indicate that carryover effects of even highly divergent migratory strategies may be minimal relative to effects of conditions experienced on breeding grounds.

In an ocean warming hotspot off south-east Australia, many species have expanded their ranges polewards, including the eastern rock lobster, Sagmariasus verreauxi. This species is likely extending its range via larval advection into Tasmanian coastal waters, which are occupied by the more commercially important southern rock lobster, Jasus edwardsii. Here, thermal tolerances of these lobster species at two life stages were investigated to assess how they may respond to warming ocean temperatures. We found that the pattern, optimum and magnitude of thermal responses differed between performance measures, life stages and species. Sagmariasus verreauxi had a warmer optimal temperature for aerobic scope and escape speed than J. edwardsii. However, J. edwardsii had a higher magnitude of escape speed, indicating higher capacity for escape performance. There were also differences between life stages within species, with the larval stage having higher variation in optimal temperatures between measures than juveniles. This inconsistency in performance optima and magnitude indicates that single performance measures at single life stages are unlikely to accurately predict whole animal performance in terms of life-time survival and fitness. However, combined results of this study suggest that with continued ocean warming, S. verreauxi is likely to continue to extend its distribution polewards and increase in abundance in Tasmania.

Populations of bacteria often undergo a lag in growth when switching conditions. Because growth lags can be large compared to typical doubling times, variations in growth lag are an important but often overlooked component of bacterial fitness in fluctuating environments. We here explore how growth lag variation is determined for the archetypical switch from glucose to lactose as a carbon source in Escherichia coli. First, we show that single-cell lags are bimodally distributed and controlled by a single-molecule trigger. That is, gene expression noise causes the population before the switch to divide into subpopulations with zero and nonzero lac operon expression. While "sensorless" cells with zero preexisting lac expression at the switch have long lags because they are unable to sense the lactose signal, any nonzero lac operon expression suffices to ensure a short lag. Second, we show that the growth lag at the population level depends crucially on the fraction of sensorless cells and that this fraction in turn depends sensitively on the growth condition before the switch. Consequently, even small changes in basal expression can significantly affect the fraction of sensorless cells, thereby population lags and fitness under switching conditions, and may thus be subject to significant natural selection. Indeed, we show that condition-dependent population lags vary across wild E. coli isolates. Since many sensory genes are naturally low expressed in conditions where their inducer is not present, bimodal responses due to subpopulations of sensorless cells may be a general mechanism inducing phenotypic heterogeneity and controlling population lags in switching environments. This mechanism also illustrates how gene expression noise can turn even a simple sensory gene circuit into a bet hedging module and underlines the profound role of gene expression noise in regulatory responses., Competing Interests: The authors have declared that no competing interests exist.

Climate change affects organisms worldwide with profound ecological and evolutionary consequences, often increasing population extinction risk. Climatic factors can increase the strength, variability, or direction of natural selection on phenotypic traits, potentially driving adaptive evolution. Phenotypic plasticity in relation to temperature can allow organisms to maintain fitness in response to increasing temperatures, thereby "buying time" for subsequent genetic adaptation and promoting evolutionary rescue. Although many studies have shown that organisms respond plastically to increasing temperatures, it is unclear if such thermal plasticity is adaptive. Moreover, we know little about how natural and sexual selection operate on thermal reaction norms, reflecting such plasticity. Here, we investigate how natural and sexual selection shape phenotypic plasticity in two congeneric and phenotypically similar sympatric insect species. We show that the thermal optima for longevity and mating success differ, suggesting temperature-dependent trade-offs between survival and reproduction in both sexes. Males in these species have similar thermal reaction norm slopes but have diverged in baseline body temperature (intercepts), being higher for the more northern species. Natural selection favored reduced thermal reaction norm slopes at high ambient temperatures, suggesting that the current level of thermal plasticity is maladaptive in the context of anthropogenic climate change and that selection now promotes thermal canalization and robustness. Our results show that ectothermic animals also at high latitudes can suffer from overheating and challenge the common view of phenotypic plasticity as being beneficial in harsh and novel environments., Competing Interests: The authors declare no competing interest.

Gene drives are genetic elements that manipulate Mendelian inheritance ratios in their favour. Understanding the forces that explain drive frequency in natural populations is a long-standing focus of evolutionary research. Recently, the possibility to create artificial drive constructs to modify pest populations has exacerbated our need to understand how drive spreads in natural populations. Here, we study the impact of polyandry on a well-known gene drive, called t haplotype, in an intensively monitored population of wild house mice. First, we show that house mice are highly polyandrous: 47% of 682 litters were sired by more than one male. Second, we find that drive-carrying males are particularly compromised in sperm competition, resulting in reduced reproductive success. As a result, drive frequency decreased during the 4.5 year observation period. Overall, we provide the first direct evidence that the spread of a gene drive is hampered by reproductive behaviour in a natural population.

A challenge in medical genomics is to identify variants and genes associated with severe genetic disorders. Based on the premise that severe, early-onset disorders often result in a reduction of evolutionary fitness, several statistical methods have been developed to predict pathogenic variants or constrained genes based on the signatures of negative selection in human populations. However, we currently lack a statistical framework to jointly predict deleterious variants and constrained genes from both variant-level features and gene-level selective constraints. Here we present such a unified approach, UNEECON, based on deep learning and population genetics. UNEECON treats the contributions of variant-level features and gene-level constraints as a variant-level fixed effect and a gene-level random effect, respectively. The sum of the fixed and random effects is then combined with an evolutionary model to infer the strength of negative selection at both variant and gene levels. Compared with previously published methods, UNEECON shows improved performance in predicting missense variants and protein-coding genes associated with autosomal dominant disorders, and feature importance analysis suggests that both gene-level selective constraints and variant-level predictors are important for accurate variant prioritization. Furthermore, based on UNEECON, we observe a low correlation between gene-level intolerance to missense mutations and that to loss-of-function mutations, which can be partially explained by the prevalence of disordered protein regions that are highly tolerant to missense mutations. Finally, we show that genes intolerant to both missense and loss-of-function mutations play key roles in the central nervous system and the autism spectrum disorders. Overall, UNEECON is a promising framework for both variant and gene prioritization., Competing Interests: The author has declared that no competing interests exist.

Inbreeding may increase the extinction risk of small populations. Yet, studies using modern genomic tools to investigate inbreeding depression in nature have been limited to single populations, and little is known about the dynamics of inbreeding depression in subdivided populations over time. Natural populations often experience different environmental conditions and differ in demographic history and genetic composition, characteristics that can affect the severity of inbreeding depression. We utilized extensive long-term data on more than 3,100 individuals from eight islands in an insular house sparrow metapopulation to examine the generality of inbreeding effects. Using genomic estimates of realized inbreeding, we discovered that inbred individuals had lower survival probabilities and produced fewer recruiting offspring than noninbred individuals. Inbreeding depression, measured as the decline in fitness-related traits per unit inbreeding, did not vary appreciably among populations or with time. As a consequence, populations with more resident inbreeding (due to their demographic history) paid a higher total fitness cost, evidenced by a larger variance in fitness explained by inbreeding within these populations. Our results are in contrast to the idea that effects of inbreeding generally depend on ecological factors and genetic differences among populations, and expand the understanding of inbreeding depression in natural subdivided populations., Competing Interests: The authors declare no competing interest.

Urinary tract infections (UTI), the second most diagnosed infectious disease worldwide, are caused primarily by uropathogenic Escherichia coli (UPEC), placing a significant financial burden on the health care system. High-throughput transposon mutagenesis combined with genome-targeted sequencing is a powerful technique to interrogate genomes for fitness genes. Genome-wide analysis of E. coli requires random libraries of at least 50,000 mutants to achieve 99.99% saturation; however, the traditional murine model of ascending UTI does not permit testing of large mutant pools due to a bottleneck during infection. To address this, an E. coli CFT073 transposon mutant ordered library of 9,216 mutants was created and insertion sites were identified. A single transposon mutant was selected for each gene to assemble a condensed library consisting of 2,913 unique nonessential mutants. Using a modified UTI model in BALB/c mice, we identified 36 genes important for colonizing the bladder, including purB , yihE , and carB Screening of the condensed library in vitro identified yigP and ubiG to be essential for growth in human urine. Additionally, we developed a novel quantitative PCR (qPCR) technique to identify genes with fitness defects within defined subgroups of related genes (e.g., genes encoding fimbriae, toxins, etc.) following UTI. The number of mutants within these subgroups circumvents bottleneck restriction and facilitates validation of multiple mutants to generate individual competitive indices. Collectively, this study investigates the bottleneck effects during UTI, provides two techniques for evading those effects that can be applied to other disease models, and contributes a genetic tool in prototype strain CFT073 to the field. IMPORTANCE Uropathogenic Escherichia coli strains cause most uncomplicated urinary tract infections (UTI), one of the most common infectious diseases worldwide. Random transposon mutagenesis techniques have been utilized to identify essential bacterial genes during infection; however, this has been met with limitations when applied to the murine UTI model. Conventional high-throughput transposon mutagenesis screens are not feasible because of inoculum size restrictions due to a bottleneck during infection. Our study utilizes a condensed ordered transposon library, limiting the number of mutants while maintaining the largest possible genome coverage. Screening of this library in vivo , and in human urine in vitro , identified numerous candidate fitness factors. Additionally, we have developed a novel technique using qPCR to quantify bacterial outputs following infection with small subgroups of transposon mutants. Molecular approaches developed in this study will serve as useful tools to probe in vivo models that are restricted by anatomical, physiological, or genetic bottleneck limitations., (Copyright © 2020 American Society for Microbiology.)

Background: Reproductive factors and hormone use in postmenopausal women have been hypothesised to affect the risk of developing lung cancer, but the epidemiological evidence is inconsistent., Methods: Using the Korean National Health Insurance System database, we identified 4,775,398 postmenopausal women older than 40 years who had undergone both cardiovascular health- and cancer screening between 1 January 2009 and 31 December 2014. Information about reproductive factors was obtained from a self-administered questionnaire. The risk of lung cancer was estimated using Cox proportional hazard regression models., Results: During a median follow-up of 4.4 years, 16,556 women (15,223 non-smokers) were diagnosed with lung cancer. The risk of lung cancer was not significantly influenced by early menarche age (adjusted hazard ratio [aHR] 1.03 for menarche ≥18 vs. ≤14; 95% confidence interval [CI], 0.98-1.09) or late age at menopause (aHR 1.02 for menopause ≥55 vs. <40; 95% CI, 0.91-1.14). Furthermore, the number of children, duration of breastfeeding and use of hormone replacement therapy were not associated with the risk of lung cancer., Conclusions: No statistically significant association was found between reproductive factors and the risk of lung cancer in postmenopausal Korean women.

Abiotic stress is a major force of selection that organisms are constantly facing. While the evolutionary effects of various stressors have been broadly studied, it is only more recently that the relevance of interactions between evolution and underlying ecological conditions, that is, eco-evolutionary feedbacks, have been highlighted. Here, we experimentally investigated how populations adapt to pH-stress under high population densities. Using the protist species Tetrahymena thermophila, we studied how four different genotypes evolved in response to stressfully low pH conditions and high population densities. We found that genotypes underwent evolutionary changes, some shifting up and others shifting down their intrinsic rates of increase (r 0 ). Overall, evolution at low pH led to the convergence of r 0 and intraspecific competitive ability (α) across the four genotypes. Given the strong correlation between r 0 and α, we argue that this convergence was a consequence of selection for increased density-dependent fitness at low pH under the experienced high density conditions. Increased density-dependent fitness was either attained through increase in r 0 , or decrease of α, depending on the genetic background. In conclusion, we show that demography can influence the direction of evolution under abiotic stress., (© 2020 The Authors. Evolution © 2020 The Society for the Study of Evolution.)

With two genomes in the same organism, interspecific hybrids have unique fitness opportunities and costs. In both plants and yeasts, wild, pathogenic, and domesticated hybrids may eliminate portions of one parental genome, a phenomenon known as loss of heterozygosity (LOH). Laboratory evolution of hybrid yeast recapitulates these results, with LOH occurring in just a few hundred generations of propagation. In this study, we systematically looked for alleles that are beneficial when lost in order to determine how prevalent this mode of adaptation may be and to determine candidate loci that might underlie the benefits of larger-scale chromosome rearrangements. These aims were accomplished by mating Saccharomyces uvarum with the S. cerevisiae deletion collection to create hybrids such that each nonessential S. cerevisiae allele is deleted. Competitive fitness assays of these pooled, barcoded, hemizygous strains, and accompanying controls, revealed a large number of loci for which LOH is beneficial. We found that the fitness effects of hemizygosity are dependent on the species context, the selective environment, and the species origin of the deleted allele. Further, we found that hybrids have a wider distribution of fitness consequences versus matched S. cerevisiae hemizygous diploids. Our results suggest that LOH can be a successful strategy for adaptation of hybrids to new environments, and we identify candidate loci that drive the chromosomal rearrangements observed in evolution of yeast hybrids., (© 2019 Lancaster et al.; Published by Cold Spring Harbor Laboratory Press.)

The soil-dwelling, saprophytic actinomycete Rhodococcus equi is a facultative intracellular pathogen of macrophages and causes severe bronchopneumonia when inhaled by susceptible foals. Standard treatment for R. equi disease is dual-antimicrobial therapy with a macrolide and rifampin. Thoracic ultrasonography and early treatment with antimicrobials prior to the development of clinical signs are used as means of controlling endemic R. equi infection on many farms. Concurrently with the increased use of macrolides and rifampin for chemoprophylaxis and the treatment of subclinically affected foals, a significant increase in the incidence of macrolide- and rifampin-resistant R. equi isolates has been documented. Previously, our laboratory demonstrated decreased fitness of R. equi strains that were resistant to macrolides, rifampin, or both, resulting in impaired in vitro growth in iron-restricted media and in soil. The objective of this study was to examine the effect of macrolide and/or rifampin resistance on intracellular replication of R. equi in equine pulmonary macrophages and in an in vivo mouse infection model in the presence and absence of antibiotics. In equine macrophages, the macrolide-resistant strain did not increase in bacterial numbers over time and the dual macrolide- and rifampin-resistant strain exhibited decreased proliferation compared to the susceptible isolate. In the mouse model, in the absence of antibiotics, the susceptible R. equi isolate outcompeted the macrolide- or rifampin-resistant strains., (Copyright © 2019 American Society for Microbiology.)

Temporal variation is a powerful source of selection on life history strategies and functional traits in natural populations. Theory predicts that the rate and predictability of fluctuations should favor distinct strategies, ranging from phenotypic plasticity to bet-hedging, which are likely to have important consequences for species distribution patterns and their responses to environmental change. To date, we have few empirical studies that test those predictions in natural systems, and little is known about how genetic, environmental, and developmental factors interact to define the "fluctuation niche" of species in temporally variable environments. In this study, we evaluated the effects of hydrological variability on fitness and functional trait variation in three closely related plant species in the genus Lasthenia that occupy different microhabitats within vernal pool landscapes. Using a controlled greenhouse experiment, we manipulated the mean and variability in hydrological conditions by growing plants at different depths with respect to a shared water table and manipulating the magnitude of stochastic fluctuations in the water table over time. We found that all species had similarly high relative fitness above the water table, but differed in their sensitivities to water table fluctuations. Specifically, the two species from vernal pools basins, where soil moisture is controlled by a perched water table, were negatively affected by the stochasticity treatments. In contrast, a species from the upland habitat surrounding vernal pools, where stochastic precipitation events control soil moisture variation, was insensitive to experimental fluctuations in the water table. We found strong signatures of genetic, environmental (plastic), and developmental variation in four traits that can influence plant hydrological responses. Three of these traits varied across plant development and among experimental treatments in directions that aligned with constitutive differences among species, suggesting that multiple sources of variation align to facilitate phenotypic matching with the hydrological environment in Lasthenia. We found little evidence for predicted patterns of phenotypic plasticity and bet-hedging in species and traits from predictable and stochastic environments, respectively. We propose that selection for developmental shifts in the hydrological traits of Lasthenia species has reduced or modified selection for plasticity at any given stage of development. Collectively, these results suggest that variation in species' sensitivities to hydrological stochasticity may explain why vernal pool Lasthenia species do not occur in upland habitat, and that all three species integrate genetic, environmental, and developmental information to manage the unique patterns of temporal hydrological variation in their respective microhabitats., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

The role of genetic relatedness in social evolution has recently come under critical attention. These arguments are here critically analyzed, both theoretically and empirically. It is argued that when the conceptual structure of the theory of natural selection is carefully taken into account, genetic relatedness can be seen to play an indispensable role in the evolution of both facultative and advanced eusociality. Although reviewing the empirical evidence concerning the evolution of eusociality reveals that relatedness does not play a role in the initial appearance of helper phenotypes, this follows simply from the fact that natural selection - of which relatedness is a necessary component - does not play a causal role in the origin of any traits. Further, separating two logically distinct elements of causal explanation - necessity and sufficiency - explains why the debate lingers on: although relatedness plays a necessary role in the evolution of helping and advanced eusociality, relatedness alone is not sufficient for their appearance. Therefore, if the relatedness variable in a given data set is held at a uniformly high value, then it indeed may turn out that other factors occupy a more prominent role. However, this does not change the fact that high relatedness functions as a necessary background condition for the evolution of advanced eusociality.

Egg size represents maternal investment and is an important life-history trait. It also is assumed to have an effect on offspring fitness. Life-history theory predicts that oviparous animals on islands will produce enlarged eggs because of increased maternal investment to improve offspring performance to facilitate intra-specific competition. The life-history theory, developed during the 1950s, provides a possible explanation for the "island rule", but this rule has seldom been tested. Although several studies have detected a positive relationship between egg size and offspring fitness, it is difficult to exclude the covarying effects on offspring performance, such as genetic variation and developmental plasticity; predictions made using the life-history theory on the islands have not been tested. In this study, we have evaluated the relationship between egg size and offspring fitness on 20 islands in the Zhoushan Archipelago and two nearby mainland sites. To exclude covarying effects, we compared larval performance among different egg sizes in three levels: among siblings within clutches, among clutches within populations, and among different islands. The results showed that frogs on most of the islands did produce enlarged eggs and that their larvae had improved larval fitness. Additionally, at all three levels, the offspring that evolved from enlarged eggs had increased offspring fitness. The results of this study indicate that, for the first time, the life-history theory predictions concerning egg size and offspring fitness are supported.

Competition between animal species can cause niche partitioning and shape an individual's phenotype, including its behaviour. However, little is known about effects of interspecific competition on personality, the among-individual variation in behaviour that is consistent across different spatial and temporal contexts. We investigated whether alien grey squirrels (Sciurus carolinensis) influenced the expression of personality traits in native red squirrels (Sciurus vulgaris). In Italy, alien grey squirrels replaced native reds through competition for food resources and space, reducing breeding and recruitment in the native species. We compared personality of red squirrels in red-only (no interspecific competition) and red-grey (with interspecific competition) sites, using arena-tests. The trait activity was measured by Open Field Test while sociability and avoidance were quantified by Mirror Image Stimulation test. Red squirrels co-occurring with the alien species had higher sociability scores and higher between-individual variation in sociability than in red-only sites. Differences in activity and avoidance were not significant. Personality - fitness relationships were not affected by presence or absence of grey squirrels, suggesting that the expression of sociability in red squirrels was not due to short-term selection, but was likely the result of context-related advantages when co-occurring with the competing species.

Ten years ago, two reviews clarified the need to tie glucocorticoid (GC) levels directly to survival and reproductive measures. Three primary hypotheses emerged from that work: the CORT-Fitness hypothesis, the CORT-Adaptation hypothesis, and the CORT-Tradeoff hypothesis. The two reviews have since been cited nearly 900 times, but no clear consensus has emerged supporting one hypothesis over another. We propose that resource availability may be a major confound across studies. Life-history investment is determined by both allocation and acquisition, but current literature testing among the three GC-fitness hypotheses rarely incorporate metrics of resource availability. In 1986, van Noordwijk and de Jong (vN and dJ) proposed the acquisition/allocation Y-model to explain positive versus negative correlations between reproduction and survival across individuals. Their model elevated resources as critical to evaluating individual allocation strategies (favoring reproduction vs. survival), and therefore provides the ideal framework for testing across the three CORT hypotheses. Here, we review the three hypotheses in light of the last 10 years of data, introduce the vN and dJ framework as a model for fitness/GC hypothesis testing, and discuss best practices for using this framework. We believe incorporation of resource availability will reduce unexplained variability in GC-fitness tests, clarify support among the three hypotheses, and allow for greater power in testing across other context dependencies (e.g., life-history strategy) that likely regulate differential allocation to reproduction versus survival as GCs increase., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

Meiotic recombination is evolutionarily ambiguous, as being associated with both benefits and costs to its bearers, with the resultant dependent on a variety of conditions. While existing theoretical models explain the emergence and maintenance of recombination, some of its essential features remain underexplored. Here we focus on one such feature, recombination plasticity, and test whether recombination response to stress is fitness-dependent. We compare desiccation stress effects on recombination rate and crossover interference in chromosome 3 between desiccation-sensitive and desiccation-tolerant Drosophila lines. We show that relative to desiccation-tolerant genotypes, desiccation-sensitive genotypes exhibit a significant segment-specific increase in single- and double-crossover frequencies across the pericentromeric region of chromosome 3. Significant changes (relaxation) in crossover interference were found for the interval pairs flanking the centromere and extending to the left arm of the chromosome. These results indicate that desiccation is a recombinogenic factor and that desiccation-induced changes in both recombination rate and crossover interference are fitness-dependent, with a tendency of less fitted individuals to produce more variable progeny. Such dependence may play an important role in the regulation of genetic variation in populations experiencing environmental challenges.

The fitness consequences of inbreeding and the individual behaviors that prevent its detrimental effects can be challenging to document in wild populations. Here, we use field and molecular data from a 17-year study of banner-tailed kangaroo rats (Dipodomys spectabilis) to quantify the relationship between inbreeding, mate kinship, and lifetime reproductive success. Using a pedigree that was reconstructed using genetic and field data within a Bayesian framework (median probability of parental assignment = 0.92, mean pedigree depth = 6 generations), we estimated both inbreeding coefficients and kinship between individuals that produced offspring (mean inbreeding coefficient = 0.07, mean mate kinship = 0.08). We also used the pedigree, in combination with census data, to generate a series of fitness estimates, ranging from survival to reproductive maturity to lifetime reproductive success. We found that the population's inbreeding load was low to moderate (0.98-4.66 haploid lethal equivalents) and increased with the time frame over which fitness was estimated (lowest for survival to maturity, highest for adult-to-adult reproductive success). Fitness decreased with increasing inbreeding coefficients. For example, lifetime reproductive success was reduced by 24% for individuals with inbreeding coefficients greater than twice the population mean. Within full sibling pairs, the sibling with less-related mates produced an average of 30% more offspring over its lifetime. These data further illustrate that inbreeding can have a negative effect on lifetime reproductive success.

The sweet potato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major agricultural pest that causes economic damages worldwide. In particular, B. tabaci MED (Mediterranean) has resulted in serious economic losses in tomato production of Korea. In this study, 1,145 B. tabaci MED females from 35 tomato greenhouses in different geographic regions were collected from 2016 to 2018 (17 populations in 2016, 13 in 2017, and five in 2018) and analyzed to investigate their population genetic structures using eight microsatellite markers. The average number of alleles per population (NA) ranged from 2.000 to 5.875, the expected heterozygosity (HE) ranged from 0.218 to 0.600, the observed heterozygosity (HO) ranged from 0.061 to 0.580, and the fixation index inbreeding coefficient (FIS) ranged from -0.391 to 0.872 over the three years of the study. Some significant correlation (p < 0.05) was present between genetic differentiations (FST) and geographical distance, and a comparatively high proportion of variation was found among the B. tabaci MED populations. The B. tabaci MED populations were divided into two well-differentiated genetic clusters within different geographic regions. Interestingly, its genetic structures converged into one genetic cluster during just one year. The reasons for this genetic change were speculated to arise from different fitness, insecticide resistance, and insect movement by human activities., Competing Interests: The authors have declared that no competing interests exist.

The process of cell competition results in the 'elimination of cells that are viable but less fit than surrounding cells'. Given the highly heterogeneous nature of our tissues, it seems increasingly likely that cells are engaged in a 'survival of the fittest' battle throughout life. The process has a myriad of positive roles in the organism: it selects against mutant cells in developing tissues, prevents the propagation of oncogenic cells and eliminates damaged cells during ageing. However, 'super-fit' cancer cells can exploit cell competition mechanisms to expand and spread. Here, we review the regulation, roles and risks of cell competition in organism development, ageing and disease., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)

Propagule pressure is a leading determinant of population establishment. Yet, an experimental understanding of how propagule size and number (two principal parts of propagule pressure) determine establishment success remains incomplete. Theoretical studies suggest that the timing between introduction events, a component of propagule number, can influence establishment success. However, this dynamic has rarely been explored experimentally. Using Escherichia coli engineered with an Allee effect, we investigated how the timing of two introduction events influences establishment. For populations introduced below the Allee threshold, establishment occurred if the time between two introduction events was sufficiently short, with the length of time between events further reduced by reducing growth rate. Interestingly, we observed that as the density of bacteria introduced in one introduction event increased, the time between introduction events that allowed for establishment increased. Using a mathematical model, we provide support that the mechanism behind these trends is the ability of the first population to modify the environment, which can pave the way for establishment of the second population. Our results provide experimental evidence that the temporal distribution of introduction events regulates establishment, furthering our understanding of propagule pressure and may have implications in invasion biology and infectious disease.

Sexual selection has manifold ecological and evolutionary consequences, making its net effect on population fitness difficult to predict. A powerful empirical test is to experimentally manipulate sexual selection and then determine how population fitness evolves. Here, we synthesise 459 effect sizes from 65 experimental evolution studies using meta-analysis. We find that sexual selection on males tends to elevate the mean and reduce the variance for many fitness traits, especially in females and in populations evolving under stressful conditions. Sexual selection had weaker effects on direct measures of population fitness such as extinction rate and proportion of viable offspring, relative to traits that are less closely linked to population fitness. Overall, we conclude that the beneficial population-level consequences of sexual selection typically outweigh the harmful ones and that the effects of sexual selection can differ between sexes and environments. We discuss the implications of these results for conservation and evolutionary biology.

Climate warming is a major cause of the global decline of coral reefs. Active reef restoration, although still in its infancy, is one of several possible ways to help restore coral cover and reef ecosystem function. The deployment of mature coral larvae onto depauperate reef substratum has been shown to significantly increase larval recruitment, providing a novel option for the delivery of ex situ bred coral stock to the reef for restoration purposes. The success of such reef restoration approaches may be improved by the use of coral larval stock augmented for climate resilience. Here we explore whether coral climate resilience can be enhanced via interspecific hybridization through hybrid vigour. Firstly, we assessed cross-fertility of four pairs of Acropora species from the Great Barrier Reef. Temporal isolation in gamete release between the Acropora species was limited, but gametic incompatibility was present with varying strength between species pairs and depending on the direction of the hybrid crosses. We subsequently examined the fitness of hybrid and purebred larvae under heat stress by comparing their survival and settlement success throughout 10 days of exposure to 28 °C, 29.5 °C and 31 °C. Fitness of the majority of Acropora hybrid larvae was similar to that of the purebred larvae of both parental species, and in some instances it was higher than that of the purebred larvae of one of the parental species. Lower hybrid fertilization success did not affect larval fitness. These findings indicate that high hybrid fitness can be achieved after overcoming partial prezygotic barriers, and that interspecific hybridization may be a tool to enhance coral recruitment and climate resilience.

Extra-pair paternity (EPP) has been suggested to improve the genetic quality of offspring, but evidence has been equivocal. Benefits of EPP may be only available to specific individuals or under certain conditions. Red-winged fairy-wrens have extremely high levels of EPP, suggesting fitness benefits might be large and available to most individuals. Furthermore, extreme philopatry commonly leads to incestuous social pairings, so inbreeding avoidance may be an important selection pressure. Here, we quantified the fitness benefits of EPP under varying conditions and across life-stages. Extra-pair offspring (EPO) did not appear to have higher fitness than within-pair offspring (WPO), neither in poor years nor in the absence of helpers-at-the-nest. However, EPP was beneficial for closely related social pairs, because inbred WPO suffered an overall 75% reduction in fitness. Inbreeding depression was nonlinear and reduced nestling body condition, first year survival and reproductive success. Our comprehensive study indicates that EPP should be favored for the 17% of females paired incestuously, but cannot explain the widespread infidelity in this species. Furthermore, our finding that fitness benefits of EPP only become apparent for a small part of the population could potentially explain the apparent absence of fitness differences in population wide comparisons of EPO and WPO., (© 2019 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.)

Recent advances in medicine and life-expectancy gains have fueled multidisciplinary research into the limits of human lifespan [1-3]. Ultimately, how long humans can live for may depend on selection favoring extended longevity in our evolutionary past [4]. Human females have an unusually extended post-reproductive lifespan, which has been explained by the fitness benefits provided from helping to raise grandchildren following menopause [5, 6]. However, formal tests of whether such grandmothering benefits wane with grandmother age and explain the observed length of post-reproductive lifespan are missing. This is critical for understanding prevailing selection pressures on longevity but to date has been overlooked as a possible mechanism driving the evolution of lifespan. Here, we use extensive data from pre-industrial humans to show that fitness gains from grandmothering are dependent on grandmother age, affecting selection on the length of post-reproductive lifespan. We find both opportunities and ability to help grandchildren declined with age, while the hazard of death of women increased greatly in their late 60s and 70s compared to menopausal ages, together implying waning selection on subsequent longevity. The presence of maternal grandmothers aged 50-75 increased grandchild survival after weaning, confirming the fitness advantage of post-reproductive lifespan. However, co-residence with paternal grandmothers aged 75+ was detrimental to grandchild survival, with those grandmothers close to death and presumably in poorer health particularly associated with lower grandchild survival. The age limitations of gaining inclusive fitness from grandmothering suggests that grandmothering can select for post-reproductive longevity only up to a certain point., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Life-history theory predicts that selection could favor the decoupling of somatic and reproductive senescence if post-reproductive lifespan (PRLS) provides additional indirect fitness benefits [1, 2]. The grandmother hypothesis proposes that prolonged PRLS evolved because post-reproductive grandmothers gain inclusive fitness benefits by helping their daughters and grandchildren [3, 4]. Because most historical human data do not report direct evidence of help, we hypothesized that geographic distance between individuals may be inversely related to their capacity to help. Using an exceptionally detailed dataset of pre-industrial French settlers in the St. Lawrence Valley during the 17 th and 18 th centuries, we assessed the potential for grandmothers to improve their inclusive fitness by helping their descendants, and we evaluated how this effect varied with geographic distance, ranging between 0 and 325 km, while accounting for potential familial genetic and environmental effects [5-9]. Grandmothers (F0) who were alive allowed their daughters (F1) to increase their number of offspring (F2) born by 2.1 and to increase their number of offspring surviving to 15 years of age by 1.1 compared to when grandmothers were dead. However, the age at first reproduction was not influenced by the life status (alive or dead) of grandmothers. As geographic distance increased, the number of offspring born and lifetime reproductive success decreased, while the age at first reproduction increased, despite the grandmother being alive in these analyses. Our study suggests that geographic proximity has the potential to modulate inclusive fitness, supporting the grandmother hypothesis, and to contribute to our understanding of the evolution of PRLS., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Steady-state protein abundance is set by four rates: transcription, translation, mRNA decay and protein decay. A given protein abundance can be obtained from infinitely many combinations of these rates. This raises the question of whether the natural rates for each gene result from historical accidents, or are there rules that give certain combinations a selective advantage? We address this question using high-throughput measurements in rapidly growing cells from diverse organisms to find that about half of the rate combinations do not exist: genes that combine high transcription with low translation are strongly depleted. This depletion is due to a trade-off between precision and economy: high transcription decreases stochastic fluctuations but increases transcription costs. Our theory quantitatively explains which rate combinations are missing, and predicts the curvature of the fitness function for each gene. It may guide the design of gene circuits with desired expression levels and noise.

Reproductive site selection is a key determinant of fitness in many taxa. However, if the site characteristics that enhance offspring survival are detrimental to the parent's survival or mating success, then complex evolutionary trade-offs occur. In the Brazilian Atlantic Forest, males of the treefrog species Aparasphenodon arapapa use the temporary water bodies in forest-floor bromeliads to court and mate. Males fit tightly into the plant with the head blocking the access and after mating, stay in the bromeliad with the offspring. Since evaporation of the temporary water body inside the bromeliad results in reproductive failure, we expected that males would simply choose the largest bromeliad tanks with the most water. We found that although this was generally true, males seemed to avoid both very large bromeliads and very high water volumes. Field observations suggested a trade-off mechanism for this pattern, whereby very large and water-filled tanks would reduce the male's ability to effectively seal the tank entrance, avoid predation, or call to mating females. Males also avoided bromeliads with leaf litter and preferred slightly inclined plants. Our results indicate that during reproductive site selection, this bromeliad-breeder needs to engage in complex trade-offs between selection pressures, balancing water requirements against the need for defense and potentially, the ability to attract a mate., Competing Interests: The authors have declared that no competing interests exist.

Human-dominated landscapes represent one of the most rapidly expanding and least-understood ecosystems on earth. Yet, we know little about which features in these landscapes promote sustainable wildlife populations. Historically, in urban areas, landowners have converted native plant communities into habitats dominated by nonnative species that are not susceptible to pest damage and require little maintenance. However, nonnative plants are also poor at supporting insects that are critical food resources for higher order consumers. Despite the logical connection, no study has examined the impact of nonnative plants on subsequent population responses of vertebrate consumers. Here, we demonstrate that residential yards dominated by nonnative plants have lower arthropod abundance, forcing resident Carolina chickadees ( Poecile carolinensis ) to switch diets to less preferred prey and produce fewer young, or forgo reproduction in nonnative sites altogether. This leads to lower reproductive success and unsustainable population growth in these yards compared with those with >70% native plant biomass. Our results reveal that properties landscaped with nonnative plants function as population sinks for insectivorous birds. To promote sustainable food webs, urban planners and private landowners should prioritize native plant species., Competing Interests: The authors declare no conflict of interest.

The recent nomination by the World Health Organization of Acinetobacter baumannii as the number one priority pathogen for the development of new antibiotics is a direct consequence of its fast evolution of pathogenicity, and in particular of multidrug resistance. While the development of new antibiotics is critical, understanding the mechanisms behind the crescent bacterial antibiotic resistance is equally relevant. Often, resistance and other bacterial virulence elements are contained on highly mobile pieces of DNA that can easily spread to other bacteria. Prophages are one of the mediators of this form of gene transfer, and have been frequently found in bacterial genomes, often offering advantageous features to the host. Here we assess the contribution of prophages for the evolution of A. baumannii pathogenicity. We found prophages to be notably diverse and widely disseminated in A. baumannii genomes. Also remarkably, A. baumannii prophages encode for multiple putative virulence factors that may be implicated in the bacterium's capacity to colonize host niches, evade the host immune system, subsist in unfavorable environments, and tolerate antibiotics. Overall our results point towards a significant contribution of prophages for the dissemination and evolution of pathogenicity in A. baumannii, and highlight their clinical relevance.

Sexual selection allows male individuals to adopt different evolutionary strategies in mating system. In this study, we determined whether dominance affected reproductive fitness of male crickets Velarifictorus aspersus during both pre-copulatory and post-copulatory selection when we excluded male-male competition. The results showed that females mated more often with male winners only during the first 2 h after a fight when male winners were more likely to produce courtship songs than losers. However, females did not retain the attached spermatophores of male winners longer than those of male losers, and the fecundity and fertilization success also did not differ significantly between females mated different times with male winners and losers. Instead, the fertilization success was positively correlated with male body weight. These results suggest that a recent wining experience increases reproductive fitness of males during pre-copulatory selection, but females may prefer larger males rather than winners during post-copulatory selection. The incoordination between pre- and post-copulatory selection may allow males to adopt different evolutionary strategies in mating system.

Premise of the Study: Organisms engage in multiple species interactions simultaneously. While pollination studies generally focus on plants and pollinators exclusively, secondary robbing, a behavior that requires other species (primary robbers) to first create access holes in corollas, is common. It has been shown that secondary robbing can reduce plants' female fitness; however, we lack knowledge about its impact on male plant fitness., Methods: We experimentally simulated primary and secondary robbing in the monocarpic perennial Ipomopsis aggregata (Polemoniaceae), quantifying indirect effects on pollinator-mediated pollen (dye) donation. We also assessed whether continual nectar removal via the floral opening has similar effects on hummingbird-pollinator behavior as continual secondary robbing through robber holes., Key Results: We found no significant indirect effects of secondary robbing on a component of Ipomopsis male fitness. Although robbing did reduce pollen (dye) donation due to avoidance of robbed plants by pollinating hummingbirds, pollen donation did not differ between the two robbing treatments. The effects of secondary robbing on hummingbird behavior resembled effects of chronic nectar removal by pollinators. Our results indicate that hummingbird pollinators may use a combination of cues, including cues given by the presence or absence of nectar, to make foraging decisions., Conclusions: Combined with prior research, this study suggests that secondary robbing is less costly to a component of male fitness than to female fitness in Ipomopsis, broadening our knowledge of the overall costs of mutualism exploitation to total plant fitness., (© 2018 Botanical Society of America.)

Phenotypic plasticity is thought to impact evolutionary trajectories by shifting trait values in a direction that is either favored by natural selection ("adaptive" plasticity) or disfavored ("nonadaptive" plasticity). However, it is unclear how commonly each of these types of plasticity occurs in natural populations. To answer this question, we measured glucosinolate defensive chemistry and reproductive fitness in over 1500 individuals of the wild perennial mustard Boechera stricta, planted in four common gardens across central Idaho, United States. Glucosinolate profiles-including total glucosinolate concentration as well as the relative abundances and overall diversity of different compounds-were strongly plastic both among habitats and within habitats. Patterns of glucosinolate plasticity varied greatly among genotypes. Plasticity among sites was predicted to affect fitness in 27.1% of cases; more often than expected by chance, glucosinolate plasticity increased rather than decreased relative fitness. In contrast, we found no evidence for within-habitat selection on glucosinolate reaction norm slopes (i.e., plasticity along a continuous environmental gradient). Together, our results indicate that glucosinolate plasticity may improve the ability of B. stricta populations to persist after migration to new habitats., (© 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.)

Microbial genotypes with similarly high proficiency at a cooperative behaviour in genetically pure groups often exhibit fitness inequalities caused by social interaction in mixed groups. Winning competitors in this scenario have been referred to as 'cheaters' in some studies. Such interaction-specific fitness inequalities, as well as social exploitation (in which interaction between genotypes increases absolute fitness), might evolve due to selection for competitiveness at the focal behaviour or might arise non-adaptively due to pleiotropy, hitchhiking or genetic drift. The bacterium Myxococcus xanthus sporulates during cooperative development of multicellular fruiting bodies. Using M. xanthus lineages that underwent experimental evolution in allopatry without selection on sporulation, we demonstrate that interaction-specific fitness inequalities and facultative social exploitation during development readily evolved indirectly among descendant lineages. Fitness inequalities between evolved genotypes were not caused by divergence in developmental speed, as faster-developing strains were not over-represented among competition winners. In competitions between ancestors and several evolved strains, all evolved genotypes produced more spores than the ancestors, including losers of evolved-versus-evolved competitions, indicating that adaptation in non-developmental contexts pleiotropically increased competitiveness for spore production. Overall, our results suggest that fitness inequalities caused by social interaction during cooperative processes may often evolve non-adaptively in natural populations., (© 2018 The Authors.)