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Data from: Persistence, impacts and environmental drivers of covert infections in invertebrate hosts

Background: Persistent covert infections of the myxozoan, Tetracapsuloides bryosalmonae, in primary invertebrate hosts (the freshwater bryozoan, Fredericella sultana) have been proposed to represent a reservoir for proliferative kidney disease in secondary fish hosts. However, we have limited understanding of how covert infections persist and vary in bryozoan populations over time and space and how they may impact these populations. In addition, previous studies have likely underestimated covert infection prevalence. To improve our understanding of the dynamics, impacts and implications of covert infections we employed a highly sensitive polymerase chain reaction (PCR) assay and undertook the first investigation of covert infections in the field over an annual period by sampling bryozoans every 45 days from three populations within each of three rivers. Results: Covert infections persisted throughout the year and prevalence varied within and between rivers, but were often > 50%. Variation in temperature and water chemistry were linked with changes in prevalence in a manner consistent with the maintenance of covert infections during periods of low productivity and thus poor growth conditions for both bryozoans and T. bryosalmonae. The presence and increased severity of covert infections reduced host growth but only when bryozoans were also investing in the production of overwintering propagules (statoblasts). However, because statoblast production is transitory, this effect is unlikely to greatly impact the capacity of bryozoan populations to act as persistent sources of infections and hence potential disease outbreaks in farmed and wild fish populations. Conclusions: We demonstrate that covert infections are widespread and persist over space and time in bryozoan populations. To our knowledge, this is the first long-term study of covert infections in a field setting. Review of the results of this and previous studies enables us to identify key questions related to the ecology and evolution of covert infection strategies and associated host-parasite interactions.

Data from: Rapid change in host specificity in a field population of the biological control organism Pasteuria penetrans

In biological control, populations of both the biological control agent and the pest have the potential to evolve, and even to coevolve. This feature marks the most powerful and unpredictable aspect of biological control strategies. In particular, evolutionary change in host specificity of the biological control agent could increase or decrease its efficacy. Here, we tested for change in host specificity in a field population of the biological control organism Pasteuria penetrans. Pasteuria penetrans is an obligate parasite of the plant parasitic nematodes Meloidogyne spp., which are major agricultural pests. From 2013 through 2016, we collected yearly samples of P. penetrans from eight plots in a field infested with M. arenaria. Plots were planted either with peanut (Arachis hypogaea) or with a rotation of peanut and soybean (Glycine max). To detect temporal change in host specificity, we tested P. penetrans samples annually for their ability to attach to (and thereby infect) four clonal lines of M. arenaria. After controlling for temporal variation in parasite abundance, we found that P. penetrans from each of the eight plots showed temporal variation in their attachment specificity to the clonal host lines. The trajectories of change in host specificity were largely unique to each plot. This result suggests that local forces, at the level of individual plots, drive change in specificity. We hypothesize that coevolution with local M. arenaria hosts may be one such force. Lastly, we observed an overall reduction in attachment using samples from rotation relative to peanut plots. This result may reflect lower abundance of P. penetrans under crop rotation, potentially due to suppressed density of host nematodes. As a whole, the results show local change in specificity on a yearly basis, consistent with evolution of a biological control organism in its ability to infect and suppress its target pest.

opencc-zeroDec 2015View details →

Data from: Host-parasitoid evolution in a metacommunity

Patch size and isolation are predicted to alter both species diversity and evolution; yet, there are few empirical examples of eco-evolutionary feedback in metacommunities. We tested three hypotheses about eco-evolutionary feedback in a gall-forming fly, Eurosta solidaginis and two of its natural enemies that select for opposite traits: (i) specialization and poor dispersal ability constrain a subset of natural enemies from occupying small and isolated patches, (ii) this constraint alters selection on the gall fly, causing phenotypic shifts towards traits resistant to generalist and dispersive enemies in small and isolated patches, and (iii) reduced dispersal evolves in small, isolated populations. We sampled patches in a natural metacommunity and found support for all hypotheses; Eurosta's specialist wasp parasitoid attacked fewer galls in small and isolated patches, generating a selection gradient that favoured small galls resistant to predation by a dispersive and generalist bird predator. Phenotype distributions matched this selection gradient, and these phenotypic differences were maintained in a common garden experiment. Finally, we found lower dispersal abilities in small and isolated patches, a phenotypic shift that aids in the maintenance of local adaptation. We suggest that the trophic rank and the species traits of consumers are central to evolution in metacommunities.

Data from: Aphid specialization on different summer hosts is associated with strong genetic differentiation and unequal symbiont communities despite a common mating habitat

Specialization on different host plants can promote evolutionary diversification of herbivorous insects. Work on pea aphids (Acyrthosiphon pisum) has contributed significantly to the understanding of this process, demonstrating that populations associated with different host plants exhibit performance trade-offs across hosts, show adaptive host choice and genetic differentiation, and possess different communities of bacterial endosymbionts. Populations specialized on different secondary host plants during the parthenogenetic summer generations are also described for the black bean aphid (Aphis fabae complex) and are usually treated as different (morphologically cryptic) subspecies. In contrast to pea aphids, however, host choice and mate choice are decoupled in black bean aphids, because populations from different summer hosts return to the same primary host plant to mate and lay overwintering eggs. This could counteract evolutionary divergence, and it is currently unknown to what extent black bean aphids using different summer hosts are indeed differentiated. We addressed this question by microsatellite genotyping and endosymbiont screening of black bean aphids collected in summer from the goosefoot Chenopodium album (subspecies A. f. fabae) and from thistles of the genus Cirsium (subspecies A. f. cirsiiacanthoides) across numerous sites in Switzerland and France. Our results show clearly that aphids from Cirsium and Chenopodium show strong and geographically consistent genetic differentiation, and that they differ in their frequencies of infection with particular endosymbionts. The dependence on a joint winter host has thus not prevented the evolutionary divergence into summer host-adapted populations that appear to have evolved mechanisms of reproductive isolation within a common mating habitat.

opencc-zeroFeb 2020View details →

Congruent population genetic structures and divergence histories in anther-smut fungi and their host plants Silene italica and the S. nutans species complex

The study of population genetic structure congruence between hosts and pathogens gives important insights into their shared phylogeographic and coevolutionary histories. We studied the population genetic structure of castrating anther-smut fungi (Microbotryum genus) and of their host plants, the Silene nutans species complex, and the morphologically and genetically close S. italica, which can be found in sympatry. Phylogeographic population genetic structure related to persistence in separate glacial refugia has been recently revealed in the S. nutans plant species complex across Western Europe, identifying several distinct lineages. We genotyped 171 associated plant-pathogen pairs of anther-smut fungi and their host plant individuals using microsatellite markers and plant chloroplastic SNPs. We found clear differentiation between fungal populations parasitizing S. nutans and S. italica plants. The population genetic structure of fungal strains parasitizing the S. nutans plant species complex mirrored the host plant genetic structure, suggesting that the pathogen was isolated in glacial refugia together with its host and/or that it has specialized on the plant genetic lineages. Using random forest approximate Bayesian computation (ABC-RF), we found that the divergence history of the fungal lineages on S. nutans was congruent with the one previously inferred for the host plant and likely occurred with ancient but no recent gene flow. Genome sequences confirmed the genetic structure and the absence of recent gene flow between fungal genetic lineages. Our analyses of host-pathogen individual pairs contribute to a better understanding of co-evolutionary histories between hosts and pathogens in natural ecosystems, in which such studies are still scarce.

opencc-zeroDec 2013View details →

Data from: Signs of a vector's adaptive choice: on the evasion of infectious hosts and parasite-induced mortality

Laboratory and field experiments have demonstrated in many cases that malaria vectors do not feed randomly, but show important preferences either for infected or non-infected hosts. These preferences are likely in part shaped by the costs imposed by the parasites on both their vertebrate and dipteran hosts. However, the effect of changes in vector behaviour on actual parasite transmission remains a debated issue. We used the natural associations between a malaria-like parasite Polychromophilus murinus, the bat fly Nycteribia kolenatii and a vertebrate host the Daubenton's bat Myotis daubentonii to test the vector's feeding preference based on the host's infection status using two different approaches: 1) controlled behavioural assays in the laboratory where bat flies could choose between a pair of hosts; 2) natural bat fly abundance data from wild-caught bats, serving as an approximation of realised feeding preference of the bat flies. Hosts with the fewest infectious stages of the parasite were most attractive to the bat flies that did switch in the behavioural assay. In line with the hypothesis of costs imposed by parasites on their vectors, bat flies carrying parasites had higher mortality. However, in wild populations, bat flies were found feeding more based on the bat's body condition, rather than its infection level. Though the absolute frequency of host switches performed by the bat flies during the assays was low, in the context of potential parasite transmission they were extremely high. The decreased survival of infected bat flies suggests that the preference for less infected hosts is an adaptive trait. Nonetheless, other ecological processes ultimately determine the vector's biting rate and thus transmission. Inherent vector preferences therefore play only a marginal role in parasite transmission in the field. The ecological processes rather than preferences per se need to be identified for successful epidemiological predictions.

Data from: The genetic architecture of ecological adaptation: intraspecific variation in host plant use by the lepidopteran crop pest Chloridea virescens

Intraspecific variation in ecologically important traits is a cornerstone of Darwin's theory of evolution by natural selection. The evolution and maintenance of this variation depends on genetic architecture, which in turn determines responses to natural selection. Some models suggest that traits with complex architectures are less likely to respond to selection than those with simple architectures, yet rapid divergence has been observed in such traits. The simultaneous evolutionary lability and genetic complexity of host plant use in the Lepidopteran subfamily Heliothinae suggest that architecture may not constrain ecological adaptation in this group. Here we investigate the response of Chloridea virescens, a generalist that feeds on diverse plant species, to selection for performance on a novel host, Physalis angulata (Solanaceae). P. angulata is the preferred host of Chloridea subflexa, a narrow specialist on the genus Physalis. In previous experiments, we found that the performance of C. subflexa on P. angulata depends on many loci of small effect distributed throughout the genome, but whether the same architecture would be involved in the generalist's adoption of P. angulata was unknown. Here we report a rapid response to selection in C. virescens for performance on P. angulata, and establish that the genetic architecture of intraspecific variation is quite similar to that of the interspecific differences in terms of the number, distribution, and effect sizes of the QTL involved. We discuss the impact of genetic architecture on the ability of Heliothine moths to respond to varying ecological selection pressures.

Data from: Host specificity of Symbiodinium variants revealed by an ITS2 metahaplotype approach

Analysis of the widely used ITS region is confounded by the presence of intragenomic variants (IGVs). In Symbiodinium, the algal symbionts of reef building corals, deep-sequencing analyses are used to characterise communities within corals, yet these analyses largely overlook IGVs. Here we consider that distinct ITS2 sequences could represent IGVs rather than distinct symbiont types and argue that symbionts can be distinguished by their proportional composition of IGVs, described as their ITS2 metahaplotype. Using our metahaplotype approach on Minimum Entropy Decomposition (MED) analysis of ITS2 sequences from the corals Acropora downingi, Cyphastrea microphthalma and Playgyra daedalea, we show the dominance of a single species-specific Symbiodinium C3 variant within each coral species. We confirm the presence of these species-specific symbionts using the psbA non-coding region. Our findings highlight the importance of accounting for IGVs in ITS2 analyses and demonstrate their capacity to resolve biological patterns that would otherwise be overlooked.

opencc-zeroJan 2020View details →

Host identity and symbiotic association affects the genetic and taxonomic diversity of the clownfish-hosting sea anemone microbiome

All eukaryotic life engages in symbioses with a diverse community of bacteria that are essential for performing basic life functions. In many cases, eukaryotic organisms form additional symbioses with other macroscopic eukaryotes. The tightly-linked physical interactions that characterize many macroscopic symbioses creates opportunities for microbial transfer, which likely affects the diversity and function of individual microbiomes, and may ultimately lead to microbiome convergence between distantly related taxa. Here, we sequence the microbiomes of five species of clownfish-hosting sea anemones that co-occur on coral reefs in the Maldives. We test the importance of evolutionary history, clownfish symbiont association, and habitat on the genetic and predicted functional diversity of the microbiome, and explore signals of microbiome convergence in anemone taxa that have evolved symbioses with clownfishes independently. Our data indicate that host identity shapes the majority of the genetic diversity of the clownfish-hosting sea anemone microbiome, but predicted functional microbial diversity analyses demonstrate a convergence among host anemone microbiomes, which reflect increased functional diversity over individuals that do not host clownfishes. Further, we identify up-regulated microbial functions in host anemones that are likely affected by clownfish presence. Taken together our study reveals an even deeper metabolic coupling between clownfishes and their host anemones, and what could be a previously unknown mutualistic benefit to anemones that are symbiotic with clownfishes

Data from: Host‐derived population genomics data provides insights into bacterial and diatom composition of the killer whale skin

Recent exploration into the interactions and relationship between hosts and their microbiota has revealed a connection between many aspects of the host's biology, health and associated micro‐organisms. Whereas amplicon sequencing has traditionally been used to characterize the microbiome, the increasing number of published population genomics data sets offers an underexploited opportunity to study microbial profiles from the host shotgun sequencing data. Here, we use sequence data originally generated from killer whale Orcinus orca skin biopsies for population genomics, to characterize the skin microbiome and investigate how host social and geographical factors influence the microbial community composition. Having identified 845 microbial taxa from 2.4 million reads that did not map to the killer whale reference genome, we found that both ecotypic and geographical factors influence community composition of killer whale skin microbiomes. Furthermore, we uncovered key taxa that drive the microbiome community composition and showed that they are embedded in unique networks, one of which is tentatively linked to diatom presence and poor skin condition. Community composition differed between Antarctic killer whales with and without diatom coverage, suggesting that the previously reported episodic migrations of Antarctic killer whales to warmer waters associated with skin turnover may control the effects of potentially pathogenic bacteria such as Tenacibaculum dicentrarchi. Our work demonstrates the feasibility of microbiome studies from host shotgun sequencing data and highlights the importance of metagenomics in understanding the relationship between host and microbial ecology.

opencc-zeroSep 2019View details →

Data from: Assessing the effects of quantitative host resistance on the life-history traits of sporulating parasites with growing lesions

Assessing life-history traits of parasites on resistant hosts is crucial in evolutionary ecology. In the particular case of sporulating pathogens with growing lesions, phenotyping is difficult because one needs to disentangle properly pathogen spread from sporulation. By considering Phytophthora infestans on potato, we use mathematical modelling to tackle this issue and refine the assessment pathogen response to quantitative host resistance. We elaborate a parsimonious leaf-scale model by convolving a lesion growth model and a sporulation function, after a latency period. This model is fitted to data obtained on two isolates inoculated on three cultivars with contrasted resistance level. Our results confirm a significant host-pathogen interaction on the various estimated traits, and a reduction of both pathogen spread and spore production, induced by host resistance. Most interestingly, we highlight that quantitative resistance also changes the sporulation function, whose mode is significantly time-lagged.This alteration of the infectious period distribution on resistant hosts may have strong impacts on the dynamics of parasite populations, and should be considered when assessing the durability of disease control tactics based on plant resistance management. This inter-disciplinary work also supports the relevance of mechanistic models for analysing phenotypic data of plant-pathogen interactions.

opencc-zeroDec 2015View details →

Data from: Identification of combinatorial host-specific signatures with a potential to affect host adaptation in influenza A H1N1 and H3N2 subtypes

Background: The underlying strategies used by influenza A viruses (IAVs) to adapt to new hosts while crossing the species barrier are complex and yet to be understood completely. Several studies have been published identifying singular genomic signatures that indicate such a host switch. The complexity of the problem suggested that in addition to the singular signatures, there might be a combinatorial use of such genomic features, in nature, defining adaptation to hosts. Results: We used computational rule-based modeling to identify combinatorial sets of interacting amino acid (aa) residues in 12 proteins of IAVs of H1N1 and H3N2 subtypes. We built highly accurate rule-based models for each protein that could differentiate between viral aa sequences coming from avian and human hosts. We found 68 host-specific combinations of aa residues, potentially associated to host adaptation on HA, M1, M2, NP, NS1, NEP, PA, PA-X, PB1 and PB2 proteins of the H1N1 subtype and 24 on M1, M2, NEP, PB1 and PB2 proteins of the H3N2 subtypes. In addition to these combinations, we found 132 novel singular aa signatures distributed among all proteins, including the newly discovered PA-X protein, of both subtypes. We showed that HA, NA, NP, NS1, NEP, PA-X and PA proteins of the H1N1 subtype carry H1N1-specific and HA, NA, PA-X, PA, PB1-F2 and PB1 of the H3N2 subtype carry H3N2-specific signatures. M1, M2, PB1-F2, PB1 and PB2 of H1N1 subtype, in addition to H1N1 signatures, also carry H3N2 signatures. Similarly M1, M2, NP, NS1, NEP and PB2 of H3N2 subtype were shown to carry both H3N2 and H1N1 host-specific signatures (HSSs). Conclusions: To sum it up, we computationally constructed simple IF-THEN rule-based models that could distinguish between aa sequences of avian and human IAVs. From the rules we identified HSSs having a potential to affect the adaptation to specific hosts. The identification of combinatorial HSSs suggests that the process of adaptation of IAVs to a new host is more complex than previously suggested. The present study provides a basis for further detailed studies with the aim to elucidate the molecular mechanisms providing the foundation for the adaptation process.

opencc-zeroDec 2019View details →

Host plant phenology, insect outbreaks and herbivore communities – the importance of timing

1. Climate change may alter the dynamics of outbreak species by changing the phenological synchrony between herbivores and their host plants. As host plant phenology has a genotypic component that may interact with climate, infestation levels among genotypes might change accordingly. When the outbreaking herbivore is active early in the season, its infestation levels may also leave a detectable imprint on herbivores colonizing the plant later in the season. 2. In this study, we first investigated how the spring phenology and genotype of Quercus robur influenced the density of the spring-active, outbreaking leaf miner Acrocercops brongniardellus. We then assessed how intraspecific density affected the performance of A. brongniardellus and how oak genotype and density of A. brongniardellus affected the insect herbivore community. 3. We found that Q. robur individuals of late spring phenology were more strongly infested by A. brongniardellus. Conspecific pupae on heavily infested oaks tended to be lighter, and fewer heterospecific insect herbivores colonized the oak later in the season. Beyond its effects through phenology, plant genotype left an imprint on herbivore species richness and on two insect herbivores. 4. Our results suggest a chain of knock-on effects from plant phenology, through the outbreaking species to the insect herbivore community. Given the finding of how phenological synchrony between the outbreak species and its host plant influences infestation levels, a shift in synchrony may then change outbreak dynamics and cause cascading effects on the insect community. 29-Oct-2019

Data from: The effect of rhizosphere microbes outweighs host plant genotype in reducing insect herbivory

Rhizosphere microbes affect plant performance, including plant resistance against insect herbivores; yet, a direct comparison of the relative influence of rhizosphere microbes vs. plant genotype on herbivory levels and on metabolites related to defense is lacking. In the crucifer Boechera stricta, we tested the effects of rhizosphere microbes and plant genotype on herbivore resistance, the primary metabolome, and select secondary metabolites. Plant populations differed significantly in the concentrations of 6 glucosinolates (GLS), secondary metabolites known to provide herbivore resistance in the Brassicaceae. The population with lower GLS levels experienced ~60% higher levels of aphid (Aphis spp.) attack; no association was observed between GLS and damage by a second herbivore, flea beetles (Altica spp.). Rhizosphere microbiome (disrupted vs. intact native microbiome) had no effect on plant GLS concentrations. However, aphid number and flea beetle damage were respectively ~3-fold and 7-fold higher among plants grown in the disrupted vs. intact native microbiome treatment. These differences may be attributable to shifts in primary metabolic pathways previously implicated in host defense against herbivores, including increases in pentose and glucoronate interconversion among plants grown with an intact microbiome. Further, native microbiomes with distinct community composition (as estimated from 16s rRNA amplicon sequencing) differed 2-fold in their effect on host plant susceptibility to aphids. The findings suggest that rhizosphere microbes, including distinct native microbiomes, can play a greater role than plant genotype in defense against insect herbivores, and act through metabolic mechanisms independent of plant genotype.

opencc-zeroDec 2013View details →

Data from: New host and lineage diversity of avian haemosporidia in the Northern Andes

The northern Andes, with their steep elevational and climate gradients, are home to an exceptional diversity of flora and fauna, particularly rich in avian species that have adapted to divergent ecological conditions. With this diversity comes the opportunity for parasites to exploit a wide breadth of avian hosts. However, little research has focused on examining the patterns of prevalence and lineage diversity of avian parasites in the Andes. Here, we screened a total of 428 birds from 19 species (representing nine families) and identified 133 infections of avian haemosporidia (31%), including lineages of Plasmodium, Haemoproteus, and Leucocytozoon. We document a higher prevalence of haemosporidia at higher elevations and lower temperatures, as well as an overall high diversity of lineages in the northern Andes, including the first sequences of haemosporidians reported in hummingbirds (31 sequences found in 11 species within the family Trochilidae). Double infections were distinguished using PHASE, which enables the separation of distinct parasite lineages. Results suggest that the ecological heterogeneity of the northern Andes that has given rise to a rich diversity of avian hosts may also be particularly conducive to parasite diversification and specialization.

opencc-zeroDec 2010View details →

Data from: Migratory divides and their consequences for dispersal, population size and parasite-host interactions

Populations of migratory birds differ in their direction of migration with neighboring populations often migrating in divergent directions separated by migratory divides. A total of 26% of 103 passerine bird species in Europe had migratory divides that were located disproportionately often along a longitudinal gradient in Central Europe, consistent with the assumption of a Quaternary glacial origin of such divides in the Iberian and Balkan peninsulas followed by re-colonization. Given that studies have shown significant genetic differentiation and reduced gene flow across migratory divides we hypothesized that an absence of migratory divides would result in elevated rates of gene flow and hence a reduced level of local adaptation. In a comparative study, species with migratory divides had larger population sizes and population densities and longer dispersal distances than species without migratory divides. Species with migratory divides tended to be habitat generalists. Bird species with migratory divides had higher richness of blood parasites and higher growth rates of Staphylococcus on their eggs during the incubation period. There was weaker cell-mediated immunity in adults and stronger cell lysis in species with migratory divides. These findings may suggest that migratory divides constitute barriers to dispersal with consequences for ecology and evolution of distributions, population sizes, habitats, and parasite-host interactions. They also suggest that migratory divides may play a role in local adaptation in host-parasite interactions.

Data from: Forest fire severity affects host plant quality and insect herbivore damage

Climate change models predict increased forest fire occurrence and severity in the near future. Forest fire disturbance affects multiple ecological interactions, but there is little evidence for how naturally-occurring fires affect plant quality and herbivore damage, which is important because plants and herbivorous insects comprisemost of the diversity in natural ecosystems and are responsible for a variety of ecosystem services. We surveyed three fires in the Rocky Mountains to investigate the effects of fire severity on wax currant (Ribes cereum), an important source of food and cover for wildlife in Colorado. We measured plant quality and herbivore damage; we found that fire severity had a significant negative effect on both measures. Notably, high severity fires decreased herbivore damage by about 50%. Furthermore, we found that the effect of fire on insect herbivore damage is mostly direct, but that indirect effects mediated through changes in plant quality are also significant. Our results have important implications for the effects of climate-driven increases in fire severity on plant-insect interactions, illustrating strong direct and weaker indirect negative effects of fire severity in a forest ecosystem.

opencc-zeroDec 2014View details →

Data from: Comparative genomics of 43 strains of Xanthomonas citri pv. citri reveals the evolutionary events giving rise to pathotypes with different host ranges

Background: The identification of factors involved in the host range definition and evolution is a pivotal challenge in the goal to predict and prevent the emergence of plant bacterial disease. To trace the evolution and find molecular differences between three pathotypes of Xanthomonas citri pv. citri that may explain their distinctive host ranges, 42 strains of X. citri pv. citri and one outgroup strain, Xanthomonas citri pv. bilvae were sequenced and compared. Results: The strains from each pathotype form monophyletic clades, with a short branch shared by the Aw and A pathotypes. Pathotype-specific recombination was detected in seven regions of the alignment. Using Ancestral Character Estimation, 426 SNPs were mapped to the four branches at the base of the A, A*, Aw and A/Aw clades. Several genes containing pathotype-specific nonsynonymous mutations have functions related to pathogenicity. The A pathotype is enriched for SNP-containing genes involved in defense mechanisms, while A* is significantly depleted for genes that are involved in transcription. The pathotypes differ by four gene islands that largely coincide with regions of recombination and include genes with a role in virulence. Both A* and Aw are missing genes involved in defense mechanisms. In contrast to a recent study, we find that there are an extremely small number of pathotype-specific gene presences and absences. Conclusions: The three pathotypes of X. citri pv. citri that differ in their host ranges largely show genomic differences related to recombination, horizontal gene transfer and single nucleotide polymorphism. We detail the phylogenetic relationship of the pathotypes and provide a set of candidate genes involved in pathotype-specific evolutionary events that could explain to the differences in host range and pathogenicity between them.

opencc-zeroDec 2010View details →

Data from: Selection and genomic differentiation during ecological speciation: isolating the contributions of host association via a comparative genome scan of Neochlamisus bebbianae leaf beetles

This study uses a comparative genome scan to evaluate the contributions of host plant related divergent selection to genetic differentiation and ecological speciation in maple- and willow-associated populations of Neochlamisus bebbianae leaf beetles. For each of 15 pairwise population comparisons, we identified "outlier loci" whose strong differentiation putatively reflects divergent selection. Of 447 AFLP loci, 15% were outliers across multiple population comparisons, and low linkage disequilibrium indicated that these outliers derived from multiple regions of the genome. Outliers were further classified as "host-specific" if repeatedly observed in "different-host" population comparisons but never in "same-host" comparisons. Outliers exhibiting the opposite pattern were analogously classified as "host-independent." Host-specific outliers represented 5% of all loci and were more frequent than host-independent outliers, thus revealing a large role for host-adaptation in population genomic differentiation. Evidence that host-related selection can promote divergence despite gene flow was provided by population trees. These were structured by host-association when datasets included host-specific outliers, but not when based on neutral loci, which united sympatric populations. Lastly, three host-specific outliers were highly differentiated in all nine different-host comparisons. Because host-adaptation promotes reproductive isolation in these beetles, these loci provide promising candidate gene regions for future molecular studies of ecological speciation.