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507 results for “symbionts”
Decreased coevolutionary potential and increased symbiont fecundity during the biological invasion of a legume-rhizobium mutualism
<p>Although most invasive species engage in mutualism, we know little about how mutualism evolves as partners colonize novel environments. Selection on cooperation and standing genetic variation for mutualism traits may differ between a mutualism's invaded and native ranges, which could alter cooperation and coevolutionary dynamics. To test for such differences, we compare mutualism traits between invaded- and native-range host-symbiont genotype combinations of the weedy legume, <i>Medicago polymorpha,</i> and its nitrogen-fixing rhizobium symbiont, <i>Ensifer medicae</i>, which have co-invaded North America. We find that mutualism benefits for plants are indistinguishable between invaded- and native-range symbioses. However, rhizobia gain greater fitness from invaded-range mutualisms than from native-range mutualisms, and this enhancement of symbiont fecundity could increase the mutualism's spread by increasing symbiont availability during plant colonization. Furthermore, mutualism traits in invaded-range symbioses show lower genetic variance and a simpler partitioning of genetic variance between host and symbiont sources, compared to native-range symbioses. This suggests that biological invasion has reduced mutualists' potential to respond to coevolutionary selection. Additionally, rhizobia bearing a locus (<i>hrrP</i>) that can enhance symbiotic fitness have more exploitative phenotypes in invaded-range than in native-range symbioses. These findings highlight the impacts of biological invasion on the evolution of mutualistic interactions.</p>
Intraspecific variation in symbiont density in an insect-microbe symbiosis
<p><span><span><span><span><span><span><span><span><span><span><span>Many insects host vertically-transmitted microbes, which can confer benefits to their hosts but are costly to maintain and regulate. A key feature of these symbioses is variation: for example, symbiont density can vary among host and symbiont genotypes. However, the evolutionary forces maintaining this variation remain unclear. We studied variation in symbiont density using the pea aphid (<i>Acyrthosiphon pisum</i>) and the bacterium <i>Regiella insecticola</i>, a symbiont that can protect its host against fungal pathogens. We found that relative symbiont density varies both between two <i>Regiella</i> phylogenetic clades and among aphid 'biotypes'. Higher-density symbiont infections are correlated with stronger survival costs, but variation in density has little effect on the protection <i>Regiella</i> provides against fungi. Instead, we found that in some aphid genotypes, a dramatic decline in symbiont density precedes the loss of a symbiont infection. Together, our data suggest that the optimal density of a symbiont infection is likely different from the perspective of aphid and microbial fitness. <i>Regiella</i> might prevent loss by maintaining high within-host densities, but hosts do not appear to benefit from higher symbiont numbers and may be advantaged by losing costly symbionts in certain environments. The standing variation in symbiont density observed in natural populations could therefore be maintained by antagonistic coevolutionary interactions between hosts and their symbiotic microbes. </span></span></span></span></span></span></span></span></span></span></span></p>
Data from: Investigating the causes and consequences of symbiont shuffling in a multi-partner reef coral symbiosis under environmental change
Dynamic symbioses may critically mediate impacts of climate change on diverse organisms, with repercussions for ecosystem persistence in some cases. On coral reefs, increases in heat-tolerant symbionts after thermal bleaching can reduce coral susceptibility to future stress. However, the relevance of this adaptive response is equivocal owing to conflicting reports of symbiont stability and change. We help reconcile this conflict by showing that change in symbiont community composition (symbiont shuffling) in Orbicella faveolata depends on the disturbance severity and recovery environment. The proportion of heat-tolerant symbionts dramatically increased following severe experimental bleaching, especially in a warmer recovery environment, but tended to decrease if bleaching was less severe. These patterns can be explained by variation in symbiont performance in the changing microenvironments created by differentially bleached host tissues. Furthermore, higher proportions of heat-tolerant symbionts linearly increased bleaching resistance but reduced photochemical efficiency, suggesting that any change in community structure oppositely impacts performance and stress tolerance. Therefore, even minor symbiont shuffling can adaptively benefit corals, although fitness effects of resulting trade-offs are difficult to predict. This work helps elucidate causes and consequences of dynamism in symbiosis, which is critical to predicting responses of multi-partner symbioses such as O. faveolata to environmental change.
Data from: Raw whole Drosophila genome sequence traces have contaminant sequences from bacterial symbionts
Many Drosophila genomes have been sequenced and assembled recently, and many more genome sequencing projects are in progress. However, Drosophila have bacterial, fungal, and protozoan symbionts, and the DNA of these symbionts may be isolated in the process of sequencing Drosophila genomes. Here, we assess how much sequence is isolated from these symbionts and if the sequence contamination affected how these Drosophila genomes were assembled. We do find raw sequence from bacterial symbionts and humans in Drosophila genome sequence traces analyzed. Surprisingly, the four most-common contaminant species were shared among the Drosophila genomes. However, we do not find evidence of bacterial sequences in two published Drosophila genome assemblies.
Data from: Tadpole body size and behavior alter the social acquisition of a defensive bacterial symbiont
Individual differences in host phenotypes can generate heterogeneity in the acquisition and transmission of microbes. Although this has become a prominent factor of disease epidemiology, host phenotypic variation might similarly underlie the transmission of microbial symbionts that defend against pathogen infection. Using green frog (Lithobates clamitans) tadpoles, we test whether body size and behavior influence the social acquisition of a skin bacterium, Janthinobacterium lividum, which in some hosts can confer protection against infection by Batrachochytrium dendrobatidis, the causative agent of the amphibian skin disease chytridiomycosis. We measured body size and boldness (time spent in an open field) of green frog tadpoles and haphazardly constructed groups of six individuals. In some groups we exposed one individual in each group to J. lividum and, in other groups, we inoculated a patch of aquarium pebbles to J. lividum. After 24hr, we swabbed each individual to estimate the presence of J. lividum on their skin. On average, tadpoles acquired nearly four times more bacteria when housed with an exposed individual compared to those housed with a patch of inoculated substrate. When tadpoles were housed with an exposed group-mate, larger and "bolder" individuals acquired more bacteria. These data suggest that phenotypically-biased acquisition of defensive symbionts might generate biased patterns of mortality from the pathogens against which they protect.
Data from: Vertically transmitted symbiont reduces host fitness along temperature gradient
Parasites with exclusive vertical transmission from host parent to offspring are an evolutionary puzzle. With parasite fitness entirely linked to host reproduction, any fitness cost for infected hosts risks their selective elimination. Environmental conditions likely influence parasite impact, and thereby the success of purely vertical transmission strategies. We tested for temperature-dependent virulence of Caedibacter taeniospiralis, a vertically transmitted bacterial symbiont of the protozoan Paramecium tetraurelia. We compared growth of infected and cured host populations at five temperatures (16-32°C). Infection reduced host density at all temperatures, with a peak at 28°C. These patterns were largely consistent across five infected Paramecium strains. Similar to Wolbachia symbionts, C. taeniospiralis may compensate fitness costs by conferring to the host a 'killer trait', targeting uninfected competitors. Considerable loss of infection at 32°C suggests that killer efficacy is not universal and that limited heat tolerance restricts the conditions for persistence of C. taeniospiralis.
Data from: Cheaper isn't always worse: more protective isolates of a defensive symbiont are less costly to the aphid host
Defences against parasites are typically associated with costs to the host that contribute to the maintenance of variation in resistance. This also applies to the defence provided by the facultative bacterial endosymbiont Hamiltonella defensa, which protects its aphid hosts against parasitoid wasps while imposing life-history costs. To investigate the cost–benefit relationship within protected hosts, we introduced multiple isolates of H. defensa to the same genetic backgrounds of black bean aphids, Aphis fabae, and we quantified the protection against their parasitoid Lysiphlebus fabarum as well as the costs to the host (reduced lifespan and reproduction) in the absence of parasitoids. Surprisingly, we observed the opposite of a trade-off. Strongly protective isolates of H. defensa reduced lifespan and lifetime reproduction of unparasitized aphids to a lesser extent than weakly protective isolates. This finding has important implications for the evolution of defensive symbiosis and highlights the need for a better understanding of how strain variation in protective symbionts is maintained.
Data from: Addicted? Reduced host resistance in populations with defensive symbionts
Heritable symbionts that protect their hosts from pathogens have been described in a wide range of insect species. By reducing the incidence or severity of infection, these symbionts have the potential to reduce the strength of selection on genes in the insect genome that increase resistance. Therefore, the presence of such symbionts may slow down the evolution of resistance. Here we investigated this idea by exposing Drosophila melanogaster populations to infection with the pathogenic Drosophila C virus (DCV) in the presence or absence of Wolbachia, a heritable symbiont of arthropods that confers protection against viruses. After nine generations of selection, we found that resistance to DCV had increased in all populations. However, in the presence of Wolbachia the resistant allele of pastrel—a gene that has a major effect on resistance to DCV—was at a lower frequency than in the symbiont-free populations. This finding suggests that defensive symbionts have the potential to hamper the evolution of insect resistance genes, potentially leading to a state of evolutionary addiction where the genetically susceptible insect host mostly relies on its symbiont to fight pathogens.
Data from: Population genomics of a symbiont in the early stages of a pest invasion
Invasive species often depend on microbial symbionts, but few studies have examined the evolutionary dynamics of symbionts during the early stages of an invasion. The insect Megacopta cribraria and its bacterial nutritional symbiont Candidatus Ishikawaella capsulata invaded the southeastern US in 2009. While M. cribraria was initially discovered on wild kudzu plants, it was found as a pest on soybeans within 1 year of infestation. Because prior research suggests Ishikawaella confers the pest status—that is, the ability to thrive on soybeans—in some Megacopta species, we performed a genomic study on Ishikawaella from US. Megacopta cribraria populations to understand the role of the symbiont in driving host plant preferences. We included Ishikawaella samples collected in the first days of the invasion in 2009 and from 23 locations across the insect's 2011 US range. The 0.75 Mb symbiont genome revealed only 47 fixed differences from the pest-conferring Ishikawaella in Japan, with only one amino acid change in a nutrition-provisioning gene. This similarity, along with a lack of fixed substitutions in the US symbiont population, indicates that Ishikawella likely arrived in the US capable of being a soybean pest. Analyses of allele frequency changes between 2009 and 2011 uncover signatures of both positive and negative selection and suggest that symbionts on soybeans and kudzu experience differential selection for genes related to nutrient provisioning. Our data reveal the evolutionary trajectory of an important insect-bacteria symbiosis in the early stages of an invasion, highlighting the role microbial symbionts may play in the spread of invasive species.
Data from: Parasitoid gene expression changes after adaptation to symbiont-protected hosts
Reciprocal selection between aphids, their protective endosymbionts, and the parasitoid wasps that prey upon them offers an opportunity to study the basis of their coevolution. We investigated adaptation to symbiont-conferred defense by rearing the parasitoid wasp Lysiphlebus fabarum on aphids (Aphis fabae) possessing different defensive symbiont strains (Hamiltonella defensa). After ten generations of experimental evolution, wasps showed increased abilities to parasitize aphids possessing the H. defensa strain they evolved with, but not aphids possessing the other strain. We show that the two symbiont strains encode different toxins, potentially creating different targets for counter-adaptation. Phenotypic and behavioral comparisons suggest that neither life history traits nor oviposition behavior differed among evolved parasitoid lineages. In contrast, comparative transcriptomics of adult female wasps identified a suite of differentially expressed genes among lineages, even when reared in a common, symbiont-free, aphid host. In concurrence with the specificity of each parasitoid lineages' infectivity, most differentially expressed parasitoid transcripts were also lineage-specific. These transcripts are enriched with putative venom toxins and contain highly expressed, potentially defensive viral particles. Together, these results suggest that wild populations of L. fabarum employ a complicated offensive arsenal with sufficient genetic variation for wasps to adapt rapidly and specifically to their hosts' microbial defenses.
Data from: Strong specificity in the interaction between parasitoids and symbiont-protected hosts
Coevolution between hosts and parasites may promote the maintenance of genetic variation in both antagonists by negative-frequency-dependence if the host-parasite interaction is genotype-specific. Here we tested for specificity in the interaction between parasitoids (Lysiphlebus fabarum) and aphid hosts (Aphis fabae) that are protected by a heritable defensive endosymbiont, the γ-proteobacterium Hamiltonella defensa. Previous studies reported a lack of genotype-specificity between unprotected aphids and parasitoids, but suggested that symbiont-conferred resistance might exhibit a higher degree of specificity. Indeed, in addition to ample variation in host resistance as well as parasitoid infectivity, we found a strong aphid clone-by-parasitoid line interaction on the rates of successful parasitism. This genotype-specificity appears to be mediated by H. defensa, highlighting the important role that endosymbionts can play in host-parasite coevolution.
Data from: Evidence for specificity in symbiont-conferred protection against parasitoids
Many insects harbour facultative symbiotic bacteria, some of which have been shown to provide resistance against natural enemies. One of the best-known protective symbionts is Hamiltonella defensa, which in pea aphid (Acyrthosiphon pisum) confers resistance against attack by parasitoid wasps in the genus Aphidius (Braconidae). We asked (i) whether this symbiont also confers protection against a phylogenetically distant group of parasitoids (Aphelinidae) and (ii) whether there are consistent differences in the effects of bacteria found in pea aphid biotypes adapted to different host plants. We found that some H. defensa strains do provide protection against an aphelinid parasitoid Aphelinus abdominalis. Hamiltonella defensa from the Lotus biotype provided high resistance to A. abdominalis and moderate to low resistance to Aphidius ervi, while the reverse was seen from Medicago biotype isolates. Aphids from Ononis showed no evidence of symbiont-mediated protection against either wasp species and were relatively vulnerable to both. Our results may reflect the different selection pressures exerted by the parasitoid community on aphids feeding on different host plants, and could help explain the maintenance of genetic diversity in bacterial symbionts.
Data from: Conditional reduction of predation risk associated with a facultative symbiont in an insect
Symbionts are widespread among eukaryotes and their impacts on the ecology and evolution of their hosts are meaningful. Most insects harbour obligate and facultative symbiotic bacteria that can influence their phenotype. In the pea aphid Acyrthosiphon pisum, an astounding symbiotic-mediated phenotype has been recently observed: when infected with the symbiotic bacteria Rickettsiella viridis, young red aphid larvae become greener at adulthood and even darker green when co-infected with Rickettsiella viridis and Hamiltonella defensa. As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested. Our results suggested that the Rickettsiella viridis infection may impact positively host survival by reducing predation risk. Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change. Aphids co-infected with Rickettsiella viridis and Hamiltonella defensa were, however, more exposed to predation suggesting an ecological cost associated with multiple infections. The underlying mechanisms and ecological consequences of these symbiotic effects are discussed.
FIGURE 11. Soricilichus kivuensis Fain, 1981. A in Review of the fur-mite genus Soricilichus Fain, 1970 (Acariformes: Chirodiscidae) — symbionts of the African shrews of the subfamily Crocidurinae (Soricomorpha: Soricidae)
FIGURE 11. Soricilichus kivuensis Fain, 1981. A—male in lateral view; B—female in lateral view.
FIGURE 13 in Review of the fur-mite genus Soricilichus Fain, 1970 (Acariformes: Chirodiscidae) — symbionts of the African shrews of the subfamily Crocidurinae (Soricomorpha: Soricidae)
FIGURE 13. Soricilichus sylvisorex sp. nov., male. A—dorsal view; B—ventral view.
FIGURE 5. Soricilichus scutisorex Fain, 1970, female. A in Review of the fur-mite genus Soricilichus Fain, 1970 (Acariformes: Chirodiscidae) — symbionts of the African shrews of the subfamily Crocidurinae (Soricomorpha: Soricidae)
FIGURE 5. Soricilichus scutisorex Fain, 1970, female. A—latero-dorsal view; B—latero-ventral view.
Quality over quantity: unraveling the contributions to cytoplasmic incompatibility caused by two coinfecting Cardinium symbionts
<p><i>Cardinium hertigii</i> is a common maternally-inherited bacterial endosymbiont of arthropods. Some <i>Cardinium</i> strains spread by increasing female fitness through the induction of cytoplasmic incompatibility (CI), which kills offspring of crosses between infected males and uninfected female hosts. CI is a two-step manipulation: first, sperm from male hosts are modified by the symbiont in a manner that causes offspring death. Second, when females are also infected, the symbiont reverses sperm modification in the egg cytoplasm, allowing offspring of infected females to survive and spread the symbiont. While <i>Cardinium</i> causes CI in many arthropod hosts, most of what is known about <i>Cardinium</i> CI stems from the symbiosis between the <i>Cardinium</i> strain <i>c</i>Eper1 and its minute parasitoid host, <i>Encarsia suzannae</i>. Here, we study a second <i>Cardinium</i> CI system in the wasp <i>Encarsia partenopea</i>. <i>Encarsia partenopea</i> harbors two <i>Cardinium</i> strains, <i>c</i>Eina2 and <i>c</i>Eina3, with the <i>c</i>Eina3 present at a much lower density than <i>c</i>Eina2. Using antibiotic treatments and crossing assays, we find that the low-density <i>c</i>Eina3 strain is responsible for CI, and that <i>c</i>Eina3 appears to modify sperm during the pupal stage, like the better known <i>c</i>Eper1. However, <i>c</i>Eina3 shows a markedly different localization pattern in male reproductive tissues. Instead of infecting sperm cells, <i>c</i>Eina3 is found in somatic cells at the base of the testis and around the seminal vesicle. This localization pattern suggests that <i>c</i>Eina3 may use a different sperm modification strategy from <i>c</i>Eper1, and highlights variation between these closely related symbioses.</p>
The early life of a leaf-cutter colony constrains symbiont vertical transmission
<p>The early life of a leaf-cutter colony is characterized by the dispersal of a female alate (winged "queen") carrying a fungal pellet, and the subsequent establishment of a foundress (workerless "queen") raising her incipient fungal garden and colony. The symbiotic roach Attaphila fungicola hitchhikes on female alates during leaf-cutter nuptial flights, which strongly suggests that roaches are vertically transmitted to foundresses and their incipient colonies; however, weak compatibility between roaches and incipient gardens may constrain roach vertical transmission. </p> <p>This dataset contains data from an experiment in which the mortality of incipient fungal gardens and foundresses were scored in treatments with or without Attaphila roaches. Additionally, in roach trials we noted whether or not the roaches disturbed fungal gardens during observational bouts conducted during the experiment (see below for more detailed description of behavioral observations). Contrary to traditional assumptions, our results indicate that roaches harm incipient gardens, suggesting that roaches are not well adapted to use vertical transmission between colonies.</p> <p class="Body"> </p>
FIGURE 1 in Diverse endobiotic symbiont fauna from the late Katian (Late Ordovician) of Estonia
FIGURE 1. Map illustrating the exposure of the Ordovician in Estonia and location of studied localities. 1- Saxby North, 2- Saxby, 3- Hosholm, 4- Paluküla, 5- Vohilaid, 6- Sutlema.
The proteome of dinoflagellate symbionts during symbiosis establishment in a model cnidarian
<p>Supplemntary tables, Data and R scripts</p>
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