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opencc-zeroAug 2020View details →

Host heterogeneity mitigates virulence evolution

Parasites often infect genetically diverse host populations, and the evolutionary trajectories of parasite populations may be shaped by levels of host heterogeneity. Mixed genotype host populations, compared to homogeneous host populations, can reduce parasite prevalence and potentially reduce rates of parasite adaptation due to tradeoffs associated with adapting to specific host genotypes. Here, we used experimental evolution to select for increased virulence in populations of the bacterial parasite Serratia marcescens exposed to either heterogenous or homogenous populations of Caenorhabditis elegans. We found that parasites exposed to heterogenous host populations evolved significantly less virulence than parasites exposed to homogeneous host populations over several hundred bacterial generations. Thus, host heterogeneity impeded parasite adaptation to host populations. While we detected tradeoffs in virulence evolution, parasite adaptation to two specific host genotypes also resulted in modestly increased virulence against the reciprocal host genotypes. These results suggest that parasite adaptation to heterogenous host populations may be impeded by both tradeoffs and a reduction in the efficacy of selection as different host genotypes exert different selective pressures on a parasite population.

opencc-zeroDec 2017View details →

Data from: Convergent shifts in host-associated microbial communities across environmentally elicited phenotypes

Morphological plasticity is a genotype-by-environment interaction that enables organisms to increase fitness across varying environments. Symbioses with diverse microbiota may aid in acclimating to this variation, but whether the associated bacteria community is phenotype-specific remains unstudied. Here we induce morphological plasticity in three species of sea urchins and measure changes in the associated bacterial community. While each host species had unique microbial communities, the expression of morphological plasticity resulted in the convergence for a phenotype-specific microbiome that was, in part, driven by differentially associating with α- and γ-proteobacteria. Furthermore, these results suggest that phenotype-specific signatures were the product of the environment, and are correlated with ingestive and digestive structures. By manipulating diet quantity over time, we also support that differentially associating with microbiota along a phenotypic continuum is bidirectional. Taken together, our data support the idea of a phenotype-specific microbial community and that phenotypic plasticity extends beyond a genotype-by-environment interaction.

opencc-by-4.0Aug 2014View details →

Figure 3 in Distinct parasitoid communities associated with host races of the leaf-mining moth Acrocercops transecta on distantly related host plants (Juglandaceae and Ericaceae)

Figure 3. Lateral view of female Aneurobracon philippinensis.

opencc-by-4.0Aug 2014View details →

Figure 2 in Distinct parasitoid communities associated with host races of the leaf-mining moth Acrocercops transecta on distantly related host plants (Juglandaceae and Ericaceae)

Figure 2. Map of Japan showing the sampling localities of Acrocercops transecta mines.

opencc-zeroAug 2020View details →

Extending the ecology of fear: Parasite-mediated sexual selection drives host response to parasites

The 'ecology of fear' describes the negative effects natural enemies have on potential victims even when those victims are not consumed or infected. Although recent work has demonstrated parasites have non-consumptive effects (NCE) on potential hosts, how these effects vary within host populations is not well understood. We investigated how NCE vary based on host risk of infection and relative cost of infection by measuring the metabolic rate (MR) of naive Drosophila nigrospiracula exposed to an ectoparasite, Macrocheles subbadius. We tested two mutually exclusive hypotheses: 1) asymmetrical costs of infection drive adaptions for stronger responses to parasite exposure; or 2) asymmetrical risks of infection drive adaptions for stronger responses to parasite exposure. In this system, male flies have higher costs of infection relative to female flies due to parasite-mediated sexual selection; similarly, virgin females experience higher costs of infection relative to mated females. Risk of infection also varies among flies because mites preferentially infect female flies over males, and mites preferentially infect mated females over virgin females. Our results were compatible with the hypothesis that costs of infection drive the strength of response to mite risk. Female flies responded to parasite exposure with a 15.1% increase in MR, while exposed males showed a stronger response with a 31.3% increase in MR. Mated females increased their MR by 34.8% during mite exposure whereas virgin females experienced an increase of 61.2%. Our findings suggest that NCE of parasites can vary based on state-dependent costs of infection.

opencc-zeroSep 2020View details →

Data from: Asymmetries affecting aggressive contests between solitary parasitoids: the effect of host species

Conflicts in animals are usually resolved based on asymmetries, where contest winners are often those that value a resource the most and/or those who have the greatest potential to retain it. In parasitoid wasps, contests between females determine which individual exploits hosts for offspring production. Previous studies on solitary parasitoids rarely considered the role of biotic factors generating phenotypic variation that could influence the strength of asymmetries. Some parasitoid species parasitize host species of various sizes, producing offspring that vary considerably in size and potentially fighting ability. In this study, we reared the egg endoparasitoid Telenomus podisi (Hymenoptera: Scelionidae) on two host species to measure the effect of body size on contest resolution and how it interacts with ownership and resource value asymmetries. Our results showed that ownership status best predicts final contest outcome when similar sized wasps fight over hosts. The frequency and outcomes of individual fights structuring contests were better explained by the difference in the number of eggs laid in the hosts by each female at a given time. When contestants varied in body size, larger intruders frequently dislodged small owners regardless of ownership and resource value asymmetries. These results imply that body size is an important factor to consider in solitary parasitoid contests and that it can overshadow the effects of other asymmetries. Our study suggests that host community diversity could have a direct effect on parasitoid contests and that biotic communities, through their effects on animal phenotypes, may play an underrated role in contest resolution.

opencc-by-4.0Oct 2020View details →

Drivers of within-host genetic diversity in acute infections of viruses

Mutations frequencies of HIV, RSV and CMV samples taken from acute infections.

opencc-zeroSep 2020View details →

Cuscuta sect. Californicae (Convolvulaceae) revisited: 'cryptic' speciation and host range differentiation

Cuscuta californica complex (sensu lato, s.l.) is a western North American group of species in which the infrastaminal scales are reduced, making the morphological delimitation of species particularly challenging. A revision of this group was prompted by the discovery of an apparent new species from central California based primarily on molecular means. Prompted by this finding, the morphological limits of C. californica s.l. species were comprehensively re-evaluated through a morphometric study. DNA sequences from plastid (trnL–F region and rbcL), nuclear ribosomal ITS and 26S rDNA, as well as a low-copy nuclear pentatricopeptide repeat (PPR) gene were used to reconstruct evolutionary relationships among taxa. Last but not least, the host range of relevant taxa was determined using herbarium specimens. Molecular results strongly supported the new species, C. difficilis, which was found to be morphologically separated from C. brachycalyx only by subtle calyx lobe and corolla tube shape differences. Despite sharing some of the hosts, all the members of C. californica s.l. exhibited a differentiation of their host ranges. An identification key and description of the new species were provided together with a discussion on the systematics and host range of C. californica s.l.. Hybridization, accompanied by plastid capture, was suggested as a possible mechanism of speciation for C. brachycalyx.

opencc-zeroSep 2020View details →

When fiction becomes fact: exaggerating host manipulation by parasites

In an era where some find fake news around every corner, the use of sensationalism has inevitably found its way into the scientific literature. This is especially the case for host manipulation by parasites, a phenomenon in which a parasite causes remarkable change in the appearance or behaviour of its host. This concept, which has deservedly garnered popular interest throughout the world in recent years, is nearly 50-years old. In the past two decades, the use of scientific metaphors, including anthropomorphisms and science fiction, to describe host manipulation has become more and more prevalent. It is possible that the repeated use of such catchy, yet misleading words in both the popular media and the scientific literature could unintentionally hamper our understanding of the complexity and extent of host manipulation, ultimately shaping its narrative in part or in full. In this commentary, the impacts of exaggerating host manipulation are brought to light by examining trends in the use of embellishing words. By looking at key examples of exaggerated claims from widely reported host-parasite systems found in the recent scientific literature, it would appear that some of the fiction surrounding host manipulation has since become fact.

opencc-zeroJul 2021View details →

Data from: Trait-based variation in host contribution to pathogen transmission across species and resource supplies

Two key knowledge gaps currently limit the development of more predictive and general models of pathogen transmission: (1) the physiological basis of heterogeneity in host contribution to pathogen transmission (reservoir potential) remains poorly understood, and (2) a general means of integrating the ecological dynamics of host communities has yet to emerge. If the traits responsible for differences in reservoir potential also modulate host community dynamics, these traits could be used to predict pathogen transmission as host communities change. In two greenhouse experiments, across 23 host species and two levels of resource supply, the reservoir potential of plant hosts increased significantly along the Leaf Economic Spectrum, a global axis of plant physiological trait covariation that features prominently in models of plant community ecology. This indicates that the traits of the Leaf Economic Spectrum underlie broad differences in reservoir potential across host species and resource supplies. Therefore, host traits could be used to integrate epidemiological models of pathogen transmission with ecological models of host community change.

opencc-zeroJan 2020View details →

Geography, seasonality, and host-associated population structure influence the fecal microbiome of a genetically depauparate Arctic mammal

The Canadian Arctic is an extreme environment with low floral and faunal diversity characterized by major seasonal shifts in temperature, moisture and daylight. Muskoxen (Ovibos moschatus) are one of few large herbivores able to survive this harsh environment. Microbiome research of the gastrointestinal tract may hold clues as to how muskoxen exist in the Arctic, but also how this species may respond to rapid environmental changes. In this study, we investigated the effects of season (spring/summer/winter), year (2007-2016), and host genetic structure on population-level microbiome variation in muskoxen from the Canadian Arctic. We utilized 16S rRNA gene sequencing to characterize the fecal microbial communities of 78 male muskoxen encompassing two population genetic clusters.<a name="_Hlk534564036"> These clusters are defined by Arctic Mainland and Island populations, including; 1) two mainland sampling locations of the Northwest Territories and Nunavut; and 2) four locations of Victoria Island. </a>Between these geographic populations, we found that differences in the microbiome reflected host-associated genetic cluster with evidence of migration. Within populations, seasonality influenced bacterial diversity with no significant differences between years of sampling. We found evidence of pathogenic bacteria, with significantly higher presence in mainland samples. Our findings demonstrate the effects of seasonality and the role of host population-level structure in driving fecal microbiome differences in a large Arctic mammal.

opencc-zeroOct 2020View details →

Predicting reservoir hosts based on early SARS-CoV-2 samples and analyzing later world-wide pandemic

The SARS-CoV-2 pandemic has raised the concern for reservoir hosts of the virus since the early-stage outbreak. To address this problem, we proposed a deep learning method, DeepHoF, based on extracting the viral genomic features, to calculate the infection likelihoods and further predict the probable hosts of novel viruses. Overcoming the limitation of sequence similarity-based methods, DeepHoF was applied to the analysis of SARS-CoV-2 in the 2020 pandemic. Using the isolates sequenced in the earliest stage of COVID-19, DeepHoF identified minks, bats, dogs and cats can be highly susceptible to SARS-CoV-2, while minks might be one of the most noteworthy reservoir hosts. Several genes of SARS-CoV-2 demonstrated their significance in determining the infection likelihood on human or the host range. With a large-scale genome analysis based on DeepHoF's computation for the later world-wide pandemic, it should not be slighted for the probably bidirectional transmission of SARS-CoV-2 between humans and minks.

opencc-by-4.0Oct 2020View details →

SAPPAN: Combined Network and Host Data

The data were acquired from a small simulated environment consisting of one Windows host (host data collection) and a router that observes all network traffic passing to the host. Two attack scenarios were performed in these small simulated environments, and data relevant to these attacks were extracted and further processed. In the case, the attack scenario was based on the Drupal web application's vulnerability, which enabled downloading and running of a malicious code that provided a remote shell to the attacker. In the case, the scenario was based on the old version of the Samba file-sharing that was vulnerable to Eternalblue attack allowing to execute commands and provide a remote shell to the attacker.  The dataset is divided into separate directories according to the attacks contained. In the case of the Drupal vulnerability scenario, datasets from a failed and successful attempt to exploit the vulnerability are included. Four datasets were created during individual phases of SMB file sharing vulnerability scenario. Each directory contains a normalized network traffic capture and corresponding host data in preformatted JSON.   Drupal Vulnerability Scenario The attack scenario is based on an old Drupal server (v 8.5.0) with known vulnerability CVE-2018-7600 (also called Drupalgeddon). This vulnerability is exploited by an attacker to remotely run code and gain access to the vulnerable server via a remote shell. This connection is realized by the Meterpreter trojan of type python/meterpreter/reverse_tcp.  The binary is created by Metasploit generator msfvenom and obfuscated using the attacker's custom obfuscation technique to bypass windows antivirus. The created binary file is delivered to the victim host using remote code execution in Drupal, based on which the "finger" command is executed to download the payload from the payload delivery server and C2 server. This trojan is then launched by an attacker using additional commands injected through the Drupal vulnerability. Once launched, it automatically establishes a connection with the attacker (remote shell) through the payload delivery and C2 server. As a result, the attacker gains full access to the system and can execute any commands (in the scenario, only the "whoami" command is executed). Two datasets were generated during the scenario and its preparation. The first was obtained during the preparatory work when the server's defense mechanisms blocked an attacker's attempt to download the file (a command "MpCmdRun.exe" is used instead of the "finger" command). The second dataset contains a complete attack performed after modifying the executed commands to overcome the mentioned defense mechanisms. Samba File Sharing Vulnerability Scenario The attack scenario is based on an unpatched Windows 7 host with known vulnerability CVE-2017-0144 (also called EternalBlue). The scenario is divided into four parts covering the individual phases of the attack and failed exploitation attempts. In the first part, the attacker performs a scan of open ports on the client device and verifies if the SMB file sharing service is vulnerable to the EternalBlue attack. In the next phase, the attacker unsuccessfully tries to exploit the vulnerability using a standard Metasploit module. This procedure does not result in a remote connection. In the third phase, a specialized exploit is used to attack the service using previously known credentials. In the fourth phase, the attacker tried another script to make the scenario more complex, enabling the attack to be performed without credentials. For each mentioned phase, a separate dataset was generated, capturing all events in the form of packet traces and corresponding host data.   Dataset Features In the case of packet capture, the dataset contains standard PCAP files containing all captured packets, including the complete application layer. The raw host data were reduced to contain only the following attributes: <ul> <li>event_id - unique Identifier of the event, assigned by a preprocessor</li> <li>event_type - a type of the event</li> <li>time_created - time when the sensor recorded the event</li> <li>event_data - event type-specific payload</li> </ul>

Data from: Egg laying rather than host quality or host feeding experience drives habitat estimation in the parasitic wasp Nasonia vitripennis

In variable environments, sampling information on habitat quality is essential for making adaptive foraging decisions. In insect parasitoids, females foraging for hosts have repeatedly been shown to employ behavioral strategies that are in line with predictions from optimal foraging models. Yet, which cues exactly are employed to sample information on habitat quality, has rarely been investigated. Using the gregarious parasitoid Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae), we provided females with different cues about hosts to elucidate, which of them would change a wasp's posterior behavior suggesting a change in information status. We employed posterior clutch size decisions on a host as proxy for a female's estimation of habitat quality. Taking into account changes in physiological state of the foraging parasitoid, we tested whether different host qualities encountered previously change the subsequent clutch size decision in females. Additionally, we investigated whether other kinds of positive experiences - such as ample time to investigate hosts, host feeding, or egg laying - would increase a wasp's estimated value of habitat quality. Contrary to our expectations, quality differences in previously encountered hosts did not affect clutch size decisions. However, we found that prior egg laying experience changes posterior egg allocation to a host, indicating a change in female information status. Host feeding and the time available for host inspection, though correlated with egg laying experience, did not seem to contribute to this change in information status.

opencc-zeroDec 2019View details →

Data for: Coevolution fails to maintain genetic variation in a host-parasite model with constant finite population size

Coevolutionary negative frequency-dependent selection has been hypothesized to maintain genetic variation in host and parasites. Despite the extensive literature pertaining to host-parasite coevolution, the dynamics of genetic variation has not been examined in a matching-alleles model (MAM) with a finite population size relative to the expectation under neutral genetic drift alone. The dynamics of the MA coevolution in an infinite population, in fact, suggests that genetic variation in these coevolving populations behaves neutrally. By comparing host heterozygosity to the expectation in a single-species model of neutral genetic drift we find that while this is also largely true in finite populations two additional phenomena arise. First, reciprocal natural selection acting on stochastic perturbations in host and pathogen allele frequencies results in a slight increase or decrease in genetic variation depending on the parameter conditions. Second, following the fixation of an allele in the parasite, selection in the MAM becomes directional, which then rapidly erodes genetic variation in the host. Hence, rather than maintain it, we find that, on average, matching-alleles coevolution depletes genetic variation.

Does genetic diversity protect host populations from parasites? A meta-analysis across natural and agricultural systems

If parasites transmit more readily between closely related hosts, then parasite burdens should decrease with increased genetic diversity of host populations. This important hypothesis is often accepted at face value - notorious epidemics of crop monocultures testify to the vulnerability of host populations that have been purged of diversity. Yet the relationship between genetic diversity and parasitism likely varies across contexts, differing between crop and non-crop hosts and between experimental and natural host populations. Here, we used a meta-analytic approach to ask if host diversity confers protection against parasites over the range of contexts in which it has been tested. We synthesized the results of 102 studies, comprising 2,004 effect sizes representing a diversity of approaches and host-parasite systems. Our results validate a protective effect of genetic diversity, while revealing significant variation in its strength across biological and empirical contexts. In experimental host populations, genetic diversity reduces parasitism by ~20% for non-crop hosts and by ~50% for crop hosts. In contrast, observational studies of natural host populations show no consistent relationship between genetic diversity and parasitism, with both strong negative and positive correlations reported. This result supports the idea that, if parasites preferentially attack close relatives, the correlation of genetic diversity with parasitism could be positive or negative depending upon the potential for host populations to evolve in response to parasite selection. Taken together, these results reinforce genetic diversity as a priority for both conservation and agriculture and emphasize the challenges inherent to drawing comparisons between controlled experimental populations and dynamic natural populations.

Data from: Multidimensional plasticity in the Glanville fritillary butterfly: larval performance is temperature, host and family specific

Variation in environmental conditions during development can lead to changes in life-history traits with long-lasting effects. Here, we study how variation in temperature and host plant, i.e. the consequences of potential maternal oviposition choices, affects a suite of life-history traits in pre-diapause larvae of the Glanville fritillary butterfly. We focus on offspring survival, larval growth rates and relative fat reserves, and pay specific attention to intraspecific variation in the responses (GxExE). Globally, thermal performance and survival curves varied between diets of two host plants, suggesting that host modifies the temperature impact, or vice versa. Additionally, we show that the relative fat content has a host-dependent, discontinuous response to developmental temperature. This implies that a potential switch in resource allocation, from more investment in growth at lower temperatures to storage at higher temperatures, is dependent on the larval diet. Interestingly, a large proportion of the variance in larval performance is explained by differences among families, or interactions with this variable. Finally, we demonstrate that these family-specific responses to the host plant remain largely consistent across thermal environments. Altogether, the results of our study underscore the importance of paying attention to intraspecific trait variation in the field of evolutionary ecology.

Fungal sporocarps house diverse and host-specific communities of fungicolous fungi

Sporocarps (fruit bodies) are the sexual reproductive stage in the life cycle of many fungi. They are highly nutritious and consequently vulnerable to grazing by birds and small mammals, and invertebrates, and can be infected by microbial and fungal parasites and pathogens. The complexity of communities thriving inside sporocarps is largely unknown. In this study, we revealed the diversity, taxonomic composition and host-preference of fungicolous fungi (i.e fungi that feed on other fungi) in sporocarps. We carried out DNA metabarcoding of the ITS2 region from 176 sporocarps of 11 wood-decay fungal host species, all collected within a forest in northeast Finland. We assessed the influence of sporocarp traits, such as lifespan, morphology and size, on the fungicolous fungal community. The level of colonisation by fungicolous fungi, measured as the proportion of non-host ITS2 reads, varied between 2.8-39.8% across the 11 host species and was largely dominated by Ascomycota. Host species was the major determinant of the community composition and diversity of fungicolous fungi, suggesting that host adaptation is important for many fungicolous fungi. Furthermore, the alpha-diversity was consistently higher in short-lived and resupinate sporocarps compared to long-lived and pileate ones, perhaps due to a more hostile environment for fungal growth in the latter too. The fungicolous fungi represented numerous lineages in the fungal tree of life, among which a significant portion was poorly represented with reference sequences in databases.

Experimental parasite community perturbation reveals associations between Sin Nombre virus and gastrointestinal nematodes in a rodent reservoir host

Individuals are often co-infected with several parasite species, yet measuring within-host interactions remains difficult in the wild. Consequently, the impact of such interactions on host fitness and epidemiology are often unknown. We used anthelmintic drugs to experimentally reduce nematode infection and measured the effects on both nematodes and the important zoonosis Sin Nombre virus (SNV) in its primary reservoir (Peromyscus spp.). Treatment significantly reduced nematode infection, but increased SNV seroprevalence. Furthermore, mice that were co-infected with both nematodes and SNV were in better condition and survived up to four times longer than uninfected or singly-infected mice. These results highlight the importance of investigating multiple parasites for understanding interindividual variation and epidemiological dynamics in reservoir populations with zoonotic transmission potential.

In vivo microbial coevolution favours host protection and plastic downregulation of immunity

Microbiota can protect their hosts from infection. The short timescales in which microbes can evolve presents the possibility that 'protective microbes' can take-over from the immune system of longer-lived hosts in the coevolutionary race against pathogens. Here, we found that coevolution between a protective bacterium (Enterococcus faecalis) and a virulent pathogen (Staphylococcus aureus) within an animal population (Caenorhabditis elegans) resulted in more disease suppression than when the protective bacterium adapted to uninfected hosts. At the same time, more protective E. faecalis populations became costlier to harbour and altered the expression of 134 host genes. Many of these genes appear to be related to the mechanism of protection, reactive oxygen species production. Crucially, more protective E. faecalis populations downregulated a key immune gene, sodh-1, known to be effective against S. aureus infection. These results suggest that a microbial line of defence is favoured by microbial coevolution and may cause hosts to plastically divest of their own immunity.