Coevolution Of Host Research Articles

Comparative Analyses of Lycodon rufozonatus and Lycodon rosozonatus Gut Microbiota in Different Regions.

The interactions between hosts and the gut microbiota are intricate and can significantly affect the ecology and evolution of both parties. Various host traits, including taxonomy, diet, social behaviour, and external factors such as prey availability and the local environment, all play an important role in shaping composition and diversity of the gut microbiogta. In this study, we explored the impact of intestinal microorganisms on the host in adapting to their respective ecological niches in two species of snakes. We collected feces from Lycodon rufozonatus and Lycodon rosozonatus from different geographical locations and used 16S rRNA gene sequencing technology to sequence the v3-v4 region. The results revealed that there was no significant difference in the alpha diversity of intestinal microorganisms between L. rufozonatus and L. rosozonatus. The gut microbiota of all individuals comprised four main phyla: Pseudomonadota, Bacteroidota, Bacillota, and Actinomycetota. At the genus level, the genus Salmonella dominated the enterobacterial microbiota in the samples from Hainan, while there was no obvious dominant genus in the enterobacterial microbiota of the samples from the other four localities. Comparative analysis of enzyme families annotated to the gut microbiota between L. rufozonatus and L. rosozonatus from the four sampling regions by CAZy carbohydrate annotation revealed that nine enzyme families differed significantly in terms of glycoside hydrolases (GHs). In addition, we compared the composition of gut microbial communities between L. rufozonatus and L. rosozonatus and investigated the impact of the differences on their functions. Our results will provide insights into the coevolution of host and gut microbes.

Insights into the Complexity and Functionality of Plant Virus Protein Phosphorylation.

Phosphorylation, the most extensive and pleiotropic form of protein posttranslation modification, is central to cellular signal transduction. Throughout the extensive co-evolution of plant hosts and viruses, modifications to phosphorylation have served multiple purposes. Such modifications highlight the evolutionary trajectories of viruses and their hosts, with pivotal roles in regulation and refinement of host-virus interactions. In plant hosts, protein phosphorylation orchestrates immune responses, enhancing the activities of defense-related proteins such as kinases and transcription factors, thereby strengthening pathogen resistance in plants. Moreover, phosphorylation influences the interactions between host and viral proteins, altering viral spread and replication within host plants. In the context of plant viruses, protein phosphorylation controls key aspects of the infection cycle, including viral protein functionality and the interplay between viruses and host plant cells, leading to effects on viral accumulation and dissemination within plant tissues. Explorations of the nuances of protein phosphorylation in plant hosts and their interactions with viruses are particularly important. This review provides a systematic summary of the biological roles of the proteins of plant viruses carrying diverse genomes in regulating infection and host responses through changes in the phosphorylation status. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Genetically similar Xanthomonas arboricola pv. pruni strains and associated phage display phenotypic and genotypic variation across 35 years

Bacteriophages (phages), viruses that infect bacteria, have key ecological and evolutionary functions in the phytobiome. Despite the importance of phages as primary drivers for bacterial evolution, phage-bacteria interactions across spatiotemporal scales in natural, agricultural settings are underexplored. With increased interest in phage-based therapies to manage bacterial pathogens, an enhanced understanding of phage genetic and functional diversity at the population level, and how this, in turn, impacts bacterial evolution and virulence, is necessary. This study presents data on the genetic similarity among Xanthomonas arboricola pv. pruni (Xap) strains isolated from different geographic locations that display different lytic phenotypes when challenged with a panel of six phage isolates collected in the same region over four decades. The minor yet significant genetic variation among this small population of Xap strains is structured by both geographic location and response to phage infection. Phage genomes are also highly similar, with conserved and diverse genomic loci that correspond to isolation year. The six phages characterized here cluster into the Kantovirinae subfamily and possibly form a new genus. Only future studies will elucidate the role of Xap and Xapφ phage genes identified here in the virulence and lysis of Xap and how these, in turn, impact bacterial spot disease outcomes. The research and tripartite pathosystem presented here provides a unique opportunity to investigate the coevolution of phage-phytobacterial pathogen-plant host in depth in an agricultural setting with the potential to monitor the rate at which phage populations contribute to bacterial genetic diversity across geographic and temporal scales.

A mean field analysis of the role of indirect transmission in emergent infection events

We developed a mathematical model to investigate the role of indirect transmission in the spread of infectious diseases, using the illustrative example of sarcoptic mange as a case study. This disease can be transmitted through direct contact between an infected host and a susceptible one, or indirectly when potential hosts encounter infectious mites and larvae deposited in the environment, commonly referred to as fomites. Our focus is on exploring the potential of these infectious reservoirs as triggers for emerging infection events and as stable reservoirs of the disease. To achieve this, our mean field compartmental model incorporates the epidemiological dynamics driven by indirect transmission via fomites. We identify different types of dynamics that the system can go into, controlled by different levels of direct and indirect transmission. Among these, we find a new regime where the disease can emerge and persist over time solely through fomites, without the necessity for direct transmission. This possibility of the system reveals an evolutionary pathway that could enable the parasite to enhance its fitness beyond host co-evolution. We also define a new threshold based on an effective reproductive number, that enables us to predict the conditions for disease persistence. Our model allows us to assess the potential effectiveness of various disease intervention measures by incorporating a feature observed in real systems. We hope this contributes to a better understanding of infectious disease outbreaks.

The evolutionary and genetic patterns of African swine fever virus

African swine fever (ASF) is a serious animal disease, and has spread to Africa, Europe and Asia, causing massive economic losses. African swine fever virus (ASFV) is transmitted from a reservoir host (warthog) to domestic pigs via a sylvatic cycle (transmission between warthogs and soft ticks) and a domestic cycle (transmission between domestic pigs) and survives by expressing a variety of genes related to virus–host interactions. We evaluated differences in codon usage patterns among ASFV genotypes and clades and explored the common and specific evolutionary and genetic characteristics of ASFV sequences. We analysed the evolutionary relationships, nucleotide compositions, codon usage patterns, selection pressures (mutational pressure and natural selection) and viral adaptation to host codon usage based on the coding sequences (CDS) of key functional genes of ASFV. AT bias was detected in the six genes analysed, irrespective of clade. The AT bias of genes (A224L, A179L, EP153R) encoding proteins involved in interaction with host cells after infection was high; among them, the AT bias of EP153R was the greatest at 78.3%. A large number of overrepresented codons were identified in EP153R, whereas there were no overrepresented codons with a relative synonymous codon usage (RSCU) value of ≥3 in B646L. In most genes, the pattern of selection pressure was similar for each clade, but in EP153R, diverse patterns of selection pressure were captured within the same clade and genotype. As a result of evaluating host adaptation based on the codon adaptation index (CAI), for B646L, E183L, CP204L and A179L, the codon usage patterns in all sequences were more similar to tick than domestic pig or wild boar. However, EP153R showed the lowest average CAI value of 0.52 when selecting tick as a reference set. The genes analysed in this study showed different magnitudes of selection pressure at the clade and genotype levels, which is likely to be related to the function of the encoded proteins and may determine key evolutionary traits of viruses, such as the level of genetic variation and host range. The diversity of codon adaptations at the genetic level in ASFV may account for differences in translational selection in ASFV hosts and provides insight into viral host adaptation and co-evolution.

How flexible parasites can outsmart their hosts for evolutionary dominance

Antagonistic coevolution between hosts and parasites substantially impacts community structure, with parasites displaying fluctuating selection or arms race dynamics during coevolution. The traditional matching alleles (MA) and gene-for-gene (GFG) models have been used to describe the dynamics and interaction of host-parasite coevolution, with these models assuming that parasites adopt a single strategy when competing with other parasites. We present a nonlinear dynamic population model that challenges this assumption, showing how a parasite that is disadvantaged under either the MA or the GFG model can win the competition by switching between the two losing strategies based on an external environmental cue, internal processes, or stochastic decision-making. This counterintuitive outcome is analogous to Parrondo's paradox, a game-theoretic concept that shows how alternating between two losing strategies can result in a winning outcome. Our numerical experiments support the validity of this model, suggesting that parasites can greatly benefit from maximum flexibility in their interactions with hosts. The flexibility of successful parasites puts an extra burden on the host defenses that have to adapt to different strategies of the parasites. These findings contribute to a deeper understanding of the coevolution of parasites and hosts, with broad implications for the evolution of complex ecological systems. Published by the American Physical Society 2024

The gut microbiota facilitate their host tolerance to extreme temperatures.

Exposure to extreme cold or heat temperature is one leading cause of weather-associated mortality and morbidity in animals. Emerging studies demonstrate that the microbiota residing in guts act as an integral factor required to modulate host tolerance to cold or heat exposure, but common and unique patterns of animal-temperature associations between cold and heat have not been simultaneously examined. Therefore, we attempted to investigate the roles of gut microbiota in modulating tolerance to cold or heat exposure in mice. The results showed that both cold and heat acutely change the body temperature of mice, but mice efficiently maintain their body temperature at conditions of chronic extreme temperatures. Mice adapt to extreme temperatures by adjusting body weight gain, food intake and energy harvest. Fascinatingly, 16 S rRNA sequencing shows that extreme temperatures result in a differential shift in the gut microbiota. Moreover, transplantation of the extreme-temperature microbiota is sufficient to enhance host tolerance to cold and heat, respectively. Metagenomic sequencing shows that the microbiota assists their hosts in resisting extreme temperatures through regulating the host insulin pathway. Our findings highlight that the microbiota is a key factor orchestrating the overall energy homeostasis under extreme temperatures, providing an insight into the interaction and coevolution of hosts and gut microbiota.

Cellular Immunity of Drosophila willistoni Reveals Novel Complexity in Insect Anti-Parasitoid Defense.

Coevolution of hosts and their parasites has shaped heterogeneity of effector hemocyte types, providing immune defense reactions with variable effectiveness. In this work, we characterize hemocytes of Drosophila willistoni, a species that has evolved a cellular immune system with extensive variation and a high degree of plasticity. Monoclonal antibodies were raised and used in indirect immunofluorescence experiments to characterize hemocyte subpopulations, follow their functional features and differentiation. Pagocytosis and parasitization assays were used to determine the functional characteristics of hemocyte types. Samples were visualized using confocal and epifluorescence microscopy. We identified a new multinucleated giant hemocyte (MGH) type, which differentiates in the course of the cellular immune response to parasitoids. These cells differentiate in the circulation through nuclear division and cell fusion, and can also be derived from the central hematopoietic organ, the lymph gland. They have a binary function as they take up bacteria by phagocytosis and are involved in the encapsulation and elimination of the parasitoid. Here, we show that, in response to large foreign particles, such as parasitoids, MGHs differentiate, have a binary function and contribute to a highly effective cellular immune response, similar to the foreign body giant cells of vertebrates.

Recombination and repeat-induced point mutation landscapes reveal trade-offs between the sexual and asexual cycles of Magnaporthe oryzae

The fungal disease caused by Magnaporthe oryzae is one of the most devastating diseases that endanger many crops worldwide. Evidence shows that sexual reproduction can be advantageous for fungal diseases as hybridization facilitates host-jumping. However, the pervasive clonal lineages of M. oryzae observed in natural fields contradict this expectation. A better understanding of the roles of recombination and the fungi-specific repeat-induced point mutation (RIP) in shaping its evolutionary trajectory is essential to bridge this knowledge gap. Here we systematically investigate the RIP and recombination landscapes in M. oryzae using a whole genome sequencing data from 252 population samples and 92 cross progenies. Our data reveal that the RIP can robustly capture the population history of M. oryzae, and we provide accurate estimations of the recombination and RIP rates across different M. oryzae clades. Significantly, our results highlight a parent-of-origin bias in both recombination and RIP rates, tightly associating with their sexual potential and variations of effector proteins. This bias suggests a critical trade-off between generating novel allelic combinations in the sexual cycle to facilitate host-jumping and stimulating transposon-associated diversification of effectors in the asexual cycle to facilitate host coevolution. These findings provide unique insights into understanding the evolution of blast fungus.

Selective strengthening of lipid metabolism and the rapid immune response of Ostrinia furnacalis larvae parasitized by Macrocentrus cingulum

The Macrocentrus cingulum is a vital endoparasitic wasp that parasites in Ostrinia furnacalis larvae. It has been widely utilized for biological control of corn borer. Although previous studies have explored how the wasps suppress the host's immunity, further research is required to determine the impact of the wasps on the host's lipid metabolism and activated immune response. In this study, high-throughput transcriptome sequencing, quantitative real-time PCR, and physiological and biochemical methods were used to investigate the balance between energy metabolism and immunity in parasitic systems. The results showed that specific genes linked to lipid metabolism and transportation were up-regulated in parasitized O. furnacalis larvae, including AKHR, AKH, apoLpIII, and FAS. Additionally, M. cingulum triggered immune responses in the parasitized larvae, leading to rapid recognition and the production of immunity effectors, such as Lysozyme and antimicrobial peptides, to protect against the invading wasps. The phenoloxidase (PO) activity was inhibited as a result of parasitization. Parasitism selectively promoted lipid metabolism and activated the immune recognition response, significantly up-regulated immune pattern recognition receptors (PRRs) and effector genes, but suppressed the PPO cascade response in O. furnacalis larvae. This study can shed light on lipid metabolism, immune response, and activating the immune recognition response for parasitoid and host co-evolution and provide insight into the biological control of O. furnacalis.

Parallel evolution and enhanced virulence upon in vivo passage of an RNA virus in Drosophila melanogaster.

Virus evolution is strongly affected by antagonistic co-evolution of virus and host. Host immunity positively selects for viruses that evade the immune response, which in turn may drive counter-adaptations in host immune genes. We investigated how host immune pressure shapes virus populations, using the fruit fly Drosophila melanogaster and its natural pathogen Drosophila C virus (DCV), as a model. We performed an experimental evolution study in which DCV was serially passaged for ten generations in three fly genotypes differing in their antiviral RNAi response: wild-type flies and flies in which the endonuclease gene Dicer-2 was either overexpressed or inactivated. All evolved virus populations replicated more efficiently in vivo and were more virulent than the parental stock. The number of polymorphisms increased in all three host genotypes with passage number, which was most pronounced in Dicer-2 knockout flies. Mutational analysis showed strong parallel evolution, as mutations accumulated in a specific region of the VP3 capsid protein in every lineage in a host genotype-independent manner. The parental tyrosine at position ninety-five of VP3 was substituted with either one of five different amino acids in fourteen out of fifteen lineages. However, no consistent amino acid changes were observed in the viral RNAi suppressor gene 1A, nor elsewhere in the genome in any of the host backgrounds. Our study indicates that the RNAi response restricts the sequence space that can be explored by viral populations. Moreover, our study illustrates how evolution towards higher virulence can be a highly reproducible, yet unpredictable process.

Restless nights when sick: ectoparasite infections alter rest-activity cycles of diurnal fish hosts.

Circadian rhythms are timekeeping mechanisms responsible for an array of biological processes. Disruption of such cycles can detrimentally affect animal health. Circadian rhythms are critical in the co-evolution of host–parasite systems, as synchronization of parasite rhythms to the host can influence infection dynamics and transmission potential. This study examines the circadian rhythms in behaviour and activity of a model fish species (Poecilia reticulata) in isolation and in shoals, both when uninfected and infected with an ectoparasite (Gyrodactylus turnbulli). Additionally, the rhythmical variance of parasite activity under different light conditions as well as rhythmical variance in parasite transmissibility was explored. Overall, infection alters the circadian rhythm of fish, causing nocturnal restlessness. Increased activity of gyrodactylids on the host's skin at night could potentially contribute to this elevated host activity. Whilst migration of gyrodactylids across the host's skin may have caused irritation to the host resulting in nocturnal restlessness, the disruption in guppy activity rhythm caused by the expression of host innate immunity cannot be excluded. We discuss the wider repercussions such behavioural responses to infection have for host health, the implications for animal behaviour studies of diurnal species as well as the application of chronotherapeutic approaches to aquaculture.

Bacteriophage-Host Interactions and Coevolution.

Bacteriophages are the most abundant entity on the planet and play very relevant roles in the diversity and abundance of their bacterial hosts. These interactions are subject to several factors, such as the first encounter of the phage with its host bacterium, in which molecular interactions are fundamental. Along with this, these interactions depend on the environment and other communities present. This chapter focuses on these phage-bacteria interactions, reviewing the knowledge of the early stage (receptor-binding proteins), host responses (resistance and counter-resistance), and ecological and evolutionary models described to date. In general, knowledge has focused on a few phage-bacteria models and has been deepened by sequencing and metagenomics. The study of phage-bacteria interactions is an essential step for the development of therapies and other applications of phages in the clinical and productive environment.

Coevolutionary stability of host-symbiont systems with mixed-mode transmission

The coevolution of hosts and symbionts based on virulence and mode of transmission is a complex and diverse biological phenomenon. We introduced a conceptual model to study the stable coexistence and coevolution of an obligate symbiont (mutualist or parasite) with mixed-mode transmission and its host. Using an age-structured Leslie model for the host, we demonstrated how the obligate symbiont could modify the host’s life history traits (survival and fecundity) and the long-term growth rate of the infected lineage. When the symbiont is vertically transmitted, we found that the host and its symbiont could maximize the infected lineage’s evolutionary success (multi-level selection). Our model showed that symbionts’ effect on host longevity and reproduction might differ, even be opposing, and their net effect might often be counterintuitive. The evolutionary stability of the ecologically stable coexistence was analyzed in the framework of coevolutionary dynamics. Moreover, we found conditions for the ecological and evolutionary stability of the resident host-symbiont pair, which does not allow invasion by rare mutants (each mutant dies out by ecological selection). We concluded that, within the context of our simplified model conditions, a host-symbiont system with mixed-mode transmission is evolutionarily stable unconditionally only if the host can maximize the Malthusian parameters of the infected and non-infected lineages using the same strategy. Finally, we performed a game-theoretical analysis of our selection situation and compared two stability definitions.

Immune Evasion Mechanism of Bacteria

The co-evolution of pathogenic bacteria and hosts has led to the development of an array of virulence genes and a set of mechanisms of defense that constitute the immune system. However, successful microbial pathogens have in turn evolved complex and efficient methods to overcome innate and adaptive immune mechanisms, which can result in disease or chronic infections. Different mechanisms are used to subvert and exploit immune systems that are shared between these diverse microbial pathogens. The success of each pathogen is directly dependent on its ability to mount an effective anti-immune response within the infected host, which can ultimately result in acute or chronic infection or pathogen clearance. In this review, some of the mechanisms by which bacterial pathogens evade host immune systems like Biofilm formation and quorum sensing, bacterial surface modulators, inhibition of cytokines, blockade of Acquired Immunity, and other mechanisms are mentioned.

A target-based discovery from a parasitic helminth as a novel therapeutic approach for autoimmune diseases

Regulatory T cells (Tregs) can alleviate the development of autoimmune and inflammatory diseases, thereby proposing their role as a new therapeutic strategy. Parasitic helminths have co-evolved with hosts to generate immunological privilege and immune tolerance through inducing Tregs. Thus, constructing a "Tregs-induction"-based discovery pipeline from parasitic helminth is a promising strategy to control autoimmune and inflammatory diseases. The gel filtration chromatography and reverse-phase high-performance liquid chromatography (RP-HPLC) were used to isolate immunomodulatory components from the egg extracts of Schistosoma japonicum. The extracted peptides were evaluated for their effects on Tregs suppressive functions using flow cytometry, ELISA and T cell suppression assay. Finally, we carried out colitis and psoriasis models to evaluate the function of Tregs induced by helminth-derived peptide invivo. Here, based on target-driven discovery strategy, we successfully identified a small 3kDa peptide (SjDX5-53) from egg extracts of schistosome, which promoted both human and murine Tregs production. SjDX5-53 presented immunosuppressive function by arresting dendritic cells (DCs) at an immature state and augmenting the proportion and suppressive capacity of Tregs. In mouse models, SjDX5-53 protected mice against autoimmune-related colitis and psoriasis through inducing Tregs and inhibiting inflammatory T-helper (Th) 1 and Th17 responses. SjDX5-53 exhibited the promising therapeutic effects in alleviating the phenotype of immune-related colitis and psoriasis. This study displayed a screening and validation pipeline of the inducer of Tregs from helminth eggs, highlighting the discovery of new biologics inspired by co-evolution of hosts and their parasites. This study was supported by the Natural Science Foundation of China (82272368) and Natural Science Foundation of Jiangsu Province (BK20211586).

Cycad phylogeny predicts host plant use of Eumaeus butterflies.

Eumaeus butterflies are obligate herbivores of Zamia, the most diverse neotropical genus of cycads. Eumaeus-Zamia interactions have been characterized mainly for species distributed in North and Central America. However, larval host plant use by the southern Eumaeus clade remains largely unknown, precluding a comprehensive study of co-evolution between the genera. Here, we combine fieldwork with museum and literature surveys to expand herbivory records for Eumaeus from 21 to 38 Zamia species. We inferred a time-calibrated phylogeny of Eumaeus to test for distinct macroevolutionary scenarios of larval host plant conservatism and co-evolution. We found a remarkable coincidence between Eumaeus and Zamia diversification, with the butterfly stem group diverging at the same time as the most recent radiation of Zamia in the Miocene. Cophylogenetic reconciliation analyses show a strong cophylogenetic signal between cycads and their butterfly herbivores. Bipartite model-based approaches indicate that this is because closely related Zamia species are used by the same Eumaeus species, suggesting larval host plant resource tracking by the butterfly herbivores. Our results highlight a case of tight evolution between Eumaeus butterflies and cycads, pointing to the generality of correlated evolution and phylogenetic tracking in plant-herbivore interactions across seed plants.

Chromosome-level analysis of the Colletotrichum graminicola genome reveals the unique characteristics of core and minichromosomes.

The fungal pathogen Colletotrichum graminicola causes the anthracnose of maize (Zea mays) and is responsible for significant yield losses worldwide. The genome of C. graminicola was sequenced in 2012 using Sanger sequencing, 454 pyrosequencing, and an optical map to obtain an assembly of 13 pseudochromosomes. We re-sequenced the genome using a combination of short-read (Illumina) and long-read (PacBio) technologies to obtain a chromosome-level assembly. The new version of the genome sequence has 13 chromosomes with a total length of 57.43 Mb. We detected 66 (23.62 Mb) structural rearrangements in the new assembly with respect to the previous version, consisting of 61 (21.98 Mb) translocations, 1 (1.41 Mb) inversion, and 4 (221 Kb) duplications. We annotated the genome and obtained 15,118 predicted genes and 3,614 new gene models compared to the previous version of the assembly. We show that 25.88% of the new assembly is composed of repetitive DNA elements (13.68% more than the previous assembly version), which are mostly found in gene-sparse regions. We describe genomic compartmentalization consisting of repeat-rich and gene-poor regions vs. repeat-poor and gene-rich regions. A total of 1,140 secreted proteins were found mainly in repeat-rich regions. We also found that ~75% of the three smallest chromosomes (minichromosomes, between 730 and 551 Kb) are strongly affected by repeat-induced point mutation (RIP) compared with 28% of the larger chromosomes. The gene content of the minichromosomes (MCs) comprises 121 genes, of which 83.6% are hypothetical proteins with no predicted function, while the mean percentage of Chr1-Chr10 is 36.5%. No predicted secreted proteins are present in the MCs. Interestingly, only 2% of the genes in Chr11 have homologs in other strains of C. graminicola, while Chr12 and 13 have 58 and 57%, respectively, raising the question as to whether Chrs12 and 13 are dispensable. The core chromosomes (Chr1-Chr10) are very different with respect to the MCs (Chr11-Chr13) in terms of the content and sequence features. We hypothesize that the higher density of repetitive elements and RIPs in the MCs may be linked to the adaptation and/or host co-evolution of this pathogenic fungus.

Coevolutionary Dynamics of Host Immune and Parasite Virulence Based on an Age-Structured Epidemic Model

Hosts can activate a defensive response to clear the parasite once being infected. To explore how host survival and fecundity are affected by host-parasite coevolution for chronic parasitic diseases, in this paper, we proposed an age-structured epidemic model with infection age, in which the parasite transmission rate and parasite-induced mortality rate are structured by the infection age. By use of critical function analysis method, we obtained the existence of the host immune evolutionary singular strategy which is a continuous singular strategy (CSS). Assume that parasite-induced mortality begins at infection age [Formula: see text] and is constant v thereafter. We got that the value of the CSS, [Formula: see text], monotonically decreases with respect to infection age [Formula: see text] (see Case (I)), while it is non-monotone if the constant v positively depends on the immune trait c (see Case (II)). This non-monotonicity is verified by numerical simulations and implies that the direction of immune evolution depends on the initial value of immune trait. Besides that, we adopted two special forms of the parasite transmission rate to study the parasite's virulence evolution, by maximizing the basic reproduction ratio [Formula: see text]. The values of the convergence stable parasite's virulence evolutionary singular strategies [Formula: see text] and [Formula: see text] increase monotonically with respect to time lag L (i.e., the time lag between the onset of transmission and mortality). At the singular strategy [Formula: see text] and [Formula: see text], we further obtained the expressions of the case mortalities [Formula: see text] and how they are affected by the time lag L. Finally, we only presented some preliminary results about host and parasite coevolution dynamics, including a general condition under which the coevolutionary singular strategy [Formula: see text] is evolutionarily stable.

The Adaptive Evolution in the Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) Revealed by the Diversity of Larval Gut Bacteria.

Insect gut microbes have important roles in host feeding, digestion, immunity, development, and coevolution with pests. The fall armyworm, Spodoptera frugiperda (Smith, 1797), is a major migratory agricultural pest worldwide. The effects of host plant on the pest's gut bacteria remain to be investigated to better understand their coevolution. In this study, differences in the gut bacterial communities were examined for the fifth and sixth instar larvae of S. frugiperda fed on leaves of different host plants (corn, sorghum, highland barley, and citrus). The 16S rDNA full-length amplification and sequencing method was used to determine the abundance and diversity of gut bacteria in larval intestines. The highest richness and diversity of gut bacteria were in corn-fed fifth instar larvae, whereas in sixth instar larvae, the richness and diversity were higher when larvae were fed by other crops. Firmicutes and Proteobacteria were dominant phyla in gut bacterial communities of fifth and sixth instar larvae. According to the LDA Effect Size (LEfSe) analysis, the host plants had important effects on the structure of gut bacterial communities in S. frugiperda. In the PICRUSt2 analysis, most predicted functional categories were associated with metabolism. Thus, the host plant species attacked by S. frugiperda larvae can affect their gut bacterial communities, and such changes are likely important in the adaptive evolution of S. frugiperda to host plants.