F supergroup <Emphasis Type="Italic">Wolbachia</Emphasis> in bush crickets: what do patterns of sequence variation reveal about this supergroup and horizontal transfer between nematodes and arthropods?

Wolbachia pipientis, an intracellular, α-proteobacterium, is commonly found in arthropods and filarial nematodes. Most infected insects are known to harbor strains of Wolbachia from supergroups A or B, whereas supergroups C and D occur only in filarial nematodes. Here, we present molecular evidence from two genes (ftsZ and 16S rDNA) that 2 Orthopterans (the bush cricket species Orocharis saltator and Hapithus agitator; Gryllidae: Eneopterinae) are infected with Wolbachia from the F supergroup. Additionally, a series of PCR tests revealed that these bush cricket specimens did not harbor nematodes, thus indicating that our positive results were not a by-product of nematodes being present in these cricket samples. Patterns of molecular variation suggest that (1) strains of F supergroup Wolbachia exhibit less genetic variation than the nematode-specific C and D supergroups but more than the A and B supergroups found in arthropods and (2) that there is no evidence of recombination within F supergroup strains. The above data support previous findings that F supergroup Wolbachia is not only harbored in both nematodes and arthropods, but that horizontal transfer has likely occurred recently between these diverse taxonomic groups (although the exact details of such horizontal transmissions remain unclear). Moreover, the limited genetic variation and lack of recombination in the F supergroup suggest that this clade of Wolbachia has radiated relatively rapidly with either (1) little time for recombination to occur or (2) selection against recombination as occurs in the mutualistic C and D strains of Wolbachia – both of which remain to be explored further.     

How Diverse Is the Genus Wolbachia? Multiple-Gene Sequencing Reveals a Putatively New Wolbachia Supergroup Recovered from Spider Mites (Acari: Tetranychidae)

At least 20% of all arthropods and some nematode species are infected with intracellular bacteria of the genus Wolbachia. This highly diverse genus has been subdivided into eight “supergroups” (A to H) on the basis of nucleotide sequence data. Here, we report the discovery of a new Wolbachia supergroup recovered from the spider mite species Bryobia species V (Acari: Tetranychidae), based on the sequences of three protein-coding genes (ftsZ, gltA, and groEL) and the 16S rRNA gene. Other tetranychid mites possess supergroup B Wolbachia strains. The discovery of another Wolbachia supergroup expands the known diversity of Wolbachia and emphasizes the high variability of the genus. Our data also clarify the existing supergroup structure and highlight the use of multiple gene sequences for robust phylogenetic analysis. In addition to previous reports of recombination between the arthropod-infecting supergroups A and B, we provide evidence for recombination between the nematode-infecting supergroups C and D. Robust delineation of supergroups is essential for understanding the origin and spread of this common reproductive parasite and for unraveling mechanisms of host adaptation and manipulation across a wide range of hosts.     

Revisiting the phylogeny of Wolbachia in Collembola

The endosymbiont Wolbachia has been detected in a few parthenogenetic collembolans sampled in Europe and America, including three species of Poduromorpha, two species of Entomobryomorpha, and two species of Neelipleona. Based on 16S rRNA and ftsZ gene sequences, most of the Wolbachia infecting parthenogenetic collembolans were characterized as members of supergroup E and showed concordant phylogeny with their hosts. However, the two neelipleonan symbionts form another unique group, indicating that Wolbachia has infected parthenogenetic collembolans multiple times. In this study, five parthenogenetic collembolan species were identified as hosts of Wolbachia, and four new Wolbachia strains were reported for four collembolan species sampled in China, respectively, including a neelipleonan strain from Megalothorax incertus (wMinc). Our results demonstrated that the Wolbachia multilocus sequence typing (MLST) system is superior to the 16S rRNA + ftsZ approach for phylogenetic analyses of collembolan Wolbachia. The MLST system assigned these Wolbachia of parthenogenetic collembolans to supergroup E as a unique clade, which included wMinc, supporting the monophyletic origin of Wolbachia in parthenogenetic collembolan species. Moreover, our data suggested supergroup E as one of the most divergent lineages in Wolbachia and revealed the discrepancy between the phylogenies of Wolbachia from parthenogenetic collembolans and their hosts, which may result from the high level of genetic divergence between collembolan Wolbachia, in association with the geographic differentiation of their hosts, or the possible horizontal transmission of Wolbachia between different collembolan species.     

Supergroup C Wolbachia,mutualist symbionts of filarial nematodes,have a distinct genome structure

Wolbachia pipientis is possibly the most widespread endosymbiont of arthropods and nematodes. While all Wolbachia strains have historically been defined as a single species, 16 monophyletic clusters of diversity (called supergroups) have been described. Different supergroups have distinct host ranges and symbiotic relationships, ranging from mutualism to reproductive manipulation. In filarial nematodes, which include parasites responsible for major diseases of humans (such as Onchocerca volvulus, agent of river blindness) and companion animals (Dirofilaria immitis, the dog heartworm), Wolbachia has an obligate mutualist role and is the target of new treatment regimens. Here, we compare the genomes of eight Wolbachia strains, spanning the diversity of the major supergroups (A–F), analysing synteny, transposable element content, GC skew and gene loss or gain. We detected genomic features that differ between Wolbachia supergroups, most notably in the C and D clades from filarial nematodes. In particular, strains from supergroup C (symbionts of O. volvulus and D. immitis) present a pattern of GC skew, conserved synteny and lack of transposable elements, unique in the Wolbachia genus. These features could be the consequence of a distinct symbiotic relationship between C Wolbachia strains and their hosts, highlighting underappreciated differences between the mutualistic supergroups found within filarial nematodes.     

Diversity and evolution of the Wolbachia endosymbionts of Bemisia (Hemiptera: Aleyrodidae) whiteflies

Wolbachia is the most prevalent symbiont described in arthropods to date. Wolbachia can manipulate host reproduction, provide nutrition to insect hosts and protect insect hosts from pathogenic viruses. So far, 13 supergroups of Wolbachia have been identified. The whitefly Bemisia tabaci is a complex containing more than 28 morphologically indistinguishable cryptic species. Some cryptic species of this complex are invasive. In this study, we report a comprehensive survey of Wolbachia in B. tabaci and its relative B. afer from 1658 insects representing 54 populations across 13 provinces of China and one state of Australia. Based on the results of PCR or sequencing of the 16S rRNA gene, the overall rates of Wolbachia infection were 79.6% and 0.96% in the indigenous and invasive Bemisia whiteflies, respectively. We detected a new Wolbachia supergroup by sequencing five molecular marker genes including 16S rRNA, groEL, gltA, hcpA, and fbpA genes. Data showed that many protein‐coding genes have limitations in detecting and classifying newly identified Wolbachia supergroups and thus raise a challenge to the known Wolbachia MLST standard analysis system. Besides, the other Wolbachia strains detected from whiteflies were clustered into supergroup B. Phylogenetic trees of whitefly mitochondrial cytochrome oxidase subunit I and Wolbachia multiple sequencing typing genes were not congruent. In addition, Wolbachia was also detected outside the special bacteriocytes in two cryptic species by fluorescence in situ hybridization, indicating the horizontal transmission of Wolbachia. Our results indicate that members of Wolbachia are far from well explored.     

Comparative Genomics of Wolbachia and the Bacterial Species Concept

The importance of host-specialization to speciation processes in obligate host-associated bacteria is well known, as is also the ability of recombination to generate cohesion in bacterial populations. However, whether divergent strains of highly recombining intracellular bacteria, such as Wolbachia, can maintain their genetic distinctness when infecting the same host is not known. We first developed a protocol for the genome sequencing of uncultivable endosymbionts. Using this method, we have sequenced the complete genomes of the Wolbachia strains wHa and wNo, which occur as natural double infections in Drosophila simulans populations on the Seychelles and in New Caledonia. Taxonomically, wHa belong to supergroup A and wNo to supergroup B. A comparative genomics study including additional strains supported the supergroup classification scheme and revealed 24 and 33 group-specific genes, putatively involved in host-adaptation processes. Recombination frequencies were high for strains of the same supergroup despite different host-preference patterns, leading to genomic cohesion. The inferred recombination fragments for strains of different supergroups were of short sizes, and the genomes of the co-infecting Wolbachia strains wHa and wNo were not more similar to each other and did not share more genes than other A- and B-group strains that infect different hosts. We conclude that Wolbachia strains of supergroup A and B represent genetically distinct clades, and that strains of different supergroups can co-exist in the same arthropod host without converging into the same species. This suggests that the supergroups are irreversibly separated and that barriers other than host-specialization are able to maintain distinct clades in recombining endosymbiont populations. Acquiring a good knowledge of the barriers to genetic exchange in Wolbachia will advance our understanding of how endosymbiont communities are constructed from vertically and horizontally transmitted genes.     

First record of the bacterial endosymbiont Wolbachia for phytophagous hoverflies from genus Merodon (Diptera: Syrphidae)

Wolbachia is a widespread bacterial endosymbiont among arthropod species. It influences the reproduction of the host species and also mitochondrial DNA diversity. Until now there were only a few studies that detected Wolbachia infections in hoverflies (Diptera: Syrphidae), and this is the first broader study with the aim of examining the incidence of Wolbachia in the hoverfly genus Merodon. The obtained results indicate an infection rate of 96% and the presence of both Wolbachia supergroup A and B, which are characteristic for most of the infected arthropod species. Additionally, the presence of multiple Wolbachia strains in the Merodon aureus group species was detected and the mitochondrial DNA COI‐based relationships of the group are discussed in the light of infection. Finally, we discuss plant‐mediated horizontal transmission of Wolbachia strains among the studied hoverfly species.     

Presence of Wolbachia in Insect Eggs Containing Antimicrobially Active Anthraquinones

Wolbachia are obligatory, cytoplasmatically inherited α-proteobacteria, which are common endosymbionts in arthropods where they may cause reproductive abnormalities. Many insects are well known to protect themselves from deleterious microorganisms by antibiotic components. In this study, we addressed the question whether Wolbachia are able to infect insects containing antimicrobial anthraquinones and anthrones, and if so, whether these genotypes of Wolbachia comprise a monophyletic cluster within one of the known supergroups. Leaf beetles of the taxon Galerucini (Galerucinae) are known to contain 1,8-dihydroxylated anthraquinones and anthrones. Also, the scale insect Dactylopius contains an anthraquinone glycoside, carminic acid. Our analyses revealed that a representative of the Galerucini, Galeruca tanaceti and Dactylopius, are indeed infected by endosymbiotic Wolbachia bacteria.Phylogenetic analysis of the wsp and ftsZ genes of these bacteria revealed that strains in G. tanaceti cluster in supergroup A, whereas those present in Dactylopius are distinctive from each other and from those of G. tanaceti. They are clustering in supergroups A and B. Wolbachia strains present in close, but anthraquinone-free relatives of G. tanaceti were shown to belong also to supergroup A. From these results, we can conclude (1) a double infection in Dactylopius, (2) that the presence of antimicrobial compounds such as anthraquinones does not necessarily protect insects from infection by Wolbachia, and (3) that genotypes of Wolbachia-infecting anthraquinone-containing insects most likely do not comprise a unique genotype. These results show that Wolbachia bacteria might be adapted to cope even with conditions usually detrimental to other bacteria and that these adaptations are widespread among Wolbachia supergroups.     

Discovery of a Novel Wolbachia Supergroup in Isoptera

Wolbachia are one of the most abundant groups of bacterial endosymbionts in the biosphere. Interest in these heritable microbes has expanded with the discovery of wider genetic diversity in undersampled host species. Here, we report on the putative discovery of a new genetic lineage, denoted supergroup H, which infects the Isopteran species Zootermopsis angusticollis and Z. nevadensis. Evidence for this novel supergroup is based on portions of new Wolbachia gene sequences from each species spanning 3.5 kilobases of DNA and the following genes: 16S rDNA, dnaA, gltA, groEL, and ftsZ. Single-gene and concatenated maximum likelihood phylogenies establish this new supergroup and validate the positioning of the other Wolbachia supergroups. This discovery is the first example of a termite Wolbachia that is highly divergent from the Isopteran Wolbachia previously described in supergroup F. This study highlights the importance of multilocus approaches to resolving Wolbachia supergroup relationships. It also suggests that surveys of Wolbachia in more earlier-originating (and undersampled) groups of arthropods are more apt to reveal novel genetic diversity.     

Wolbachia effects in natural populations of Chorthippus parallelus from the Pyrenean hybrid zone

We evaluate for the first time the effect of Wolbachia infection, involving two different supergroups, on the structure and dynamics of the hybrid zone between two subspecies of Chorthippus parallelus (Orthoptera) in the Pyrenees. Wolbachia infection showed no effects on female fecundity or a slight increment in females infected by F supergroup, although in the last case it has to be well established. Cytoplasmic incompatibility (CI) is confirmed in crosses carried out in the field between individuals from a natural hybrid population. This CI, registered as the relative reduction in embryo production (s_h), was of s_h = 0.355 and s_h = 0.286 in unidirectional crosses involving B and F supergroups, respectively. CI also occurred in bidirectional crosses (s_h = 0.147) but with a weaker intensity. The transmission rates of the two Wolbachia strains (B and F) were estimated by the optimization of a theoretical model to reach the infection frequencies observed in certain population. To fit this scenario, both supergroups should present transmission rates close to 1. Further, we have simulated the infection dynamics, and hence, the capacity of Wolbachia to structure the population of the host insects and to affect to reproduction and genetic introgression in the hybrid zone. This represents a first example of the influence of Wolbachia in an insect natural hybrid zone.     

Wolbachia prevalence patterns: horizontal transmission,recombination, and multiple infections in chestnut gall wasp-parasitoid communities

The Oriental chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), is a global invasive pest that causes serious damage to almost all chestnut species belonging to the Castanea genus (Fagaceae). Dryocosmus zhuili Liu et Zhu is a recently described sibling species of D. kuriphilus, which induces galls on Castanea henryi (Skan) Rehd. et Wils. There are many indigenous parasitoid species in China which play an important role in the natural regulation of their population dynamics. Wolbachia is a maternally inherited α-proteobacterium widely found in arthropods. This study screened for the presence of Wolbachia in the two chestnut gall wasps and in six parasitoid species from 12 populations, to investigate the prevalence patterns of Wolbachia in the chestnut gall wasp-parasitoid communities. We found that D. zhuili and four parasitoid species were infected with Wolbachia; among them, all individuals of the two populations of Megastigmus sp. had multiple Wolbachia infections. By using multilocus sequence types to characterize bacterial strains, three new sequence types were identified. The Wolbachia strains infecting D. zhuili (ST-507), Torymus sinensis Kamijo (ST-508), and Sycophila variegata (Curtis) (ST-508) belonged to supergroup A, whereas the Wolbachia strain infecting Megastigmus nipponicus Kamijo (ST-503) belonged to supergroup B. Our results also suggested that horizontal transmission of Wolbachia occurs between chestnut gall wasps and their parasitoids. Moreover, multiple Wolbachia infections of Megastigmus sp. may be due to gene recombination and horizontal transmission.     

<Emphasis Type="Italic">Wolbachia</Emphasis>-induced cytoplasmic incompatibility in Japanese populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Intracellular bacteria of the genus Wolbachia (alpha Proteobacteria) induce cytoplasmic incompatibility (CI) in many arthropod species, including spider mites, but not all Wolbachia cause CI. In spider mites CI becomes apparent by a reduced egg hatchability and a lower daughter:son ratio: CI in haplodiploid organisms in general was expected to produce all-male offspring or a male-biased sex ratio without any death of eggs. In a previous study of Japanese populations of Tetranychus urticae, two out of three green-form populations tested were infected with non-CI Wolbachia strains, whereas none of six red-form populations harbored Wolbachia. As the survey of Wolbachia infection in T. urticae is still fragmentary in Japan, we checked Wolbachia infection in thirty green-form populations and 29 red-form populations collected from a wide range of Japanese islands. For Wolbachia-infected populations, we tested the effects of Wolbachia on the reproductive traits and determined the phylogenetic relationships of the different strains of Wolbachia. All but one green-form populations were infected with Wolbachia and all strains belonged to the subgroup Ori when the wsp gene was used to determine the phylogenetic relationships of different strains of Wolbachia. Six out of 29 red-form populations harbored Wolbachia and the infected strains belonged to the subgroups Ori and Bugs. Twenty-four of 29 infected green-form populations and five of six infected red-form populations induced CI among the hosts. Thus, CI-Wolbachia strains are widespread in Japan, and no geographical trend was observed in the CI-Wolbachia. Although three red-form populations harbored other intracellular bacteria Cardinium, they did not affect host reproduction.     

<Emphasis Type="Italic">Wolbachia</Emphasis> Strains Typing in Different Geographic Population Spider, <Emphasis Type="Italic">Hylyphantes Graminicola</Emphasis> (Linyphiidae)

The Wolbachia endosymbiont of spiders has not been extensively examined. In order to investigate the distribution, evolutionary history, and reproductive phenotype of Wolbachia in spiders in China, we tested 11 geographic populations of Hylyphantes graminicola. Wolbachia infection has been detected in each population. 10 Wolbachia strains have been characterized by multilocus sequence typing (MLST). Phylogenetic analyses indicated that eight Wolbachia strains in H. graminicola belonged to supergroup B, and two belonged to supergroup A. No correlation existed between Wolbachia diversity and host’s geographic distance. The significant correlation was observed between pairwise distance of H. graminicola COI and genetic divergence of associated Wolbachia strains. We also found that Wolbachia infection frequencies in hosts varied over geographic space.     

Wolbachia infection in six species of gall wasps and their parasitoids

Wolbachia are endosymbiotic bacteria that are widely present in nematodes and arthropods and sometimes have a significant impact on the evolution, ecology, and biology of their hosts. The co-occurrence of Wolbachia within both Cynipid gall wasps and their parasitoids has rarely been studied. In this study, we report the occurrence of six species of gall wasps and 10 species of their parasitoids in central China. Wolbachia detection using the wsp gene showed that Wolbachia infected two species of gall wasps as well as their parasitoids, indicating that horizontal transmission of Wolbachia occurs between gall wasps and their parasitoids. Given that parasitoids will kill their hosts, Wolbachia may be horizontally transferred from gall wasps to their parasitoids. Using multilocus sequence typing (MLST) analysis, five new strains of Wolbachia were identified, all of which belonged to supergroup A. The strains of Wolbachia that infected gall wasps were not the same as those that infected their parasitoids. This result indicated that Wolbachia may evolve independently in parasitoids after they have been transferred from the host gall wasps.     

Negative evidence of parthenogenesis induction by Wolbachia in a gallwasp species, Dryocosmus kuriphilus

The alpha‐proteobacteria of the genus Wolbachia is a widespread group of maternally inherited endosymbionts of arthropod and nematode hosts. Wolbachia infection induces a range of host phenotypes, including cytoplasmic incompatibility, male killing, feminization, and induction of thelytokous parthenogenesis. Heterogony (cyclical parthenogenesis) is a remarkable characteristic of oak gallwasps, Cynipini, the largest tribe of the Cynipidae. A few species of Cynipini are exceptional in that they are univoltine and exhibit thelytokous parthenogenesis, probably because they lost the arrhenotokous generation of their heterogonic ancestor species due to Wolbachia infection. In this study, the presence of Wolbachia was detected using polymerase chain reaction primers for the wsp genes in a thelytokous parthenogenetic species [Dryocosmus kuriphilus (Yasumatsu)] (Hymenoptera: Cynipidae: Cynipini). Approximately 29.8 and 87.1% of adults of the Zhuzhou and Fuzhou strains, respectively, were infected with Wolbachia while all females of the remaining four strains collected from other localities in China were Wolbachia free. The length of the wsp fragment of Zhuzhou and Fuzhou strains was found to be 573 and 561 bp, respectively. The nucleotide sequence of the bacterial wsp fragment indicated that the endosymbiotic bacteria of the Zhuzhou and Fuzhou strains are members of supergroup A, but belong to different clades; they probably originated from two independent infection events. In conclusion, thelytokous parthenogenesis of D. kuriphilus is not caused by Wolbachia infection and the deletion of the arrhenotokous generation is thus not associated with such an infection.     

Wolbachia strains in cryptic species of the Anastrepha fraterculus complex (Diptera,Tephritidae) along the Neotropical Region

Infection by Wolbachia was described previously in eleven species of Anastrepha fruit flies some of which are important pests of fruticulture. One such species is the nominal Anastrepha fraterculus, the South American fruit fly, which actually comprises a complex of cryptic species. The suggestions of using Wolbachia for the control of these pest species, make imperative a more precise characterization of the existing strains of the bacteria. In this study, population samples of the A. fraterculus complex from Brazil, Argentina, Peru, Ecuador, Colombia, Guatemala and Mexico were analyzed for Wolbachia infection. The bacteria were genotyped by the MLST and WSP Typing methodologies. All samples were infected with Wolbachia of supergroup “A”. For each of the five MLST genes, unique as well as already known alleles were detected. Nineteen sequence types for the concatenated sequences of the five MLST genes, and twenty wsp alleles were found in the samples. Host-specific haplotypes, shared strains among distinct hosts, and more than one strain of Wolbachia were found in some population samples. Recombination among the MLST genes and intragenic recombination between wsp haplotypes was rare. Phylogenetic analysis showed a great similarity among the Wolbachia strains in the A. fraterculus complex. However, some strains of Wolbachia are found throughout the Neotropical Region and there are specific strains in determined geographical areas.     

Genetic distinctness of parthenogenetic forms of European Polydrusus weevils of the subgenus Scythodrusus

Abstract Among eight species of Polydrusus weevils which belong to subgenus Scythodrusus, at least two possess parthenogenetic forms: P. (S.) inustus and P. (S.) pilifer. Both of these species consist of dioecious populations in the Caspian area and of parthenogenetic populations in Eastern Europe (P. (S.) inustus), the Caucasus region (both species) and Middle Asia (P. (S.) pilifer). The origin of parthenogenesis in this subgenus is unresolved; however some data suggest that the parthenogenetic forms are of hybrid ancestry. The genetic distinctness of parthenogenetic Scythodrusus was assessed on the basis of COII, ITS2, EF1‐α and Wolbachiawsp, 16S ribosomal DNA, ftsZ and hcpA sequence comparisons. Both taxa turned out to be monophyletic for all markers, which is an evidence against hybridization of their dioecious ancestors. On the other hand, a high frequency of heterozygous P. (S.) inustus females suggests an origin resulting from hybridization between genetically distinct dioecious representatives of this species. Very similar strains of Wolbachia supergroup A were found in both species, indicating that they have been either inherited from a common ancestor or were transmitted between parthenogenetic Scythodrusus weevils and probably spread randomly across their ranges.     

Absence of <Emphasis Type="Italic">Wolbachia</Emphasis> in Nonfilariid Worms Parasitizing Arthropods

Wolbachia are strictly intracellular maternally inherited α-proteobacteria, largely widespread among arthropods and filariids (i.e., filarial nematodes). Wolbachia capacities to infect new host species have been greatly evidenced and the transfer of Wolbachia between arthropods and filariids has probably occurred more than once. Interestingly, among nematode species, Wolbachia infection was found in filariids but not in closely related lineages. Their occurrence in filariids has been supposed a consequence of the parasitic lifestyle of worms within Wolbachia-infected arthropods, implying that nonfilariid worms parasitizing arthropods are also likely to be infected by some Wolbachia acquired from their hosts. To further investigate this hypothesis, we have examined seven species of nonfilariid worms of Nematoda and Nematomorpha phyla, all interacting intimately with arthropods. Wolbachia infection in nonfilariid parasitic worms was never detected by polymerase chain reaction assays of the 16S rDNA and wsp genes. By contrast, some arthropod hosts are well infected by Wolbachia of the B supergroup. Then the intimate contact with infected arthropods is not a sufficient condition to explain the Wolbachia occurrence in filariids and could underline a physiological singularity or a particular evolutionary event to acquire and maintain Wolbachia infection.     

Are ecological communities the seat of endosymbiont horizontal transfer and diversification? A case study with soil arthropod community

Maternally inherited endosymbionts of arthropods are one of the most abundant and diverse group of bacteria. These bacterial endosymbionts also show extensive horizontal transfer to taxonomically unrelated hosts and widespread recombination in their genomes. Such horizontal transfers can be enhanced when different arthropod hosts come in contact like in an ecological community. Higher rates of horizontal transfer can also increase the probability of recombination between endosymbionts, as they now share the same host cytoplasm. However, reports of community‐wide endosymbiont data are rare as most studies choose few host taxa and specific ecological interactions among the hosts. To better understand endosymbiont spread within host populations, we investigated the incidence, diversity, extent of horizontal transfer, and recombination of three endosymbionts (Wolbachia, Cardinium, and Arsenophonus) in a specific soil arthropod community. Wolbachia strains were characterized with MLST genes whereas 16S rRNA gene was used for Cardinium and Arsenophonus. Among 3,509 individual host arthropods, belonging to 390 morphospecies, 12.05% were infected with Wolbachia, 2.82% with Cardinium and 2.05% with Arsenophonus. Phylogenetic incongruence between host and endosymbiont indicated extensive horizontal transfer of endosymbionts within this community. Three cases of recombination between Wolbachia supergroups and eight incidences of within‐supergroup recombination were also found. Statistical tests of similarity indicated supergroup A Wolbachia and Cardinium show a pattern consistent with extensive horizontal transfer within the community but not for supergroup B Wolbachia and Arsenophonus. We highlight the importance of extensive community‐wide studies for a better understanding of the spread of endosymbionts across global arthropod communities.     

Contrasting patterns of molecular diversity and Wolbachia infection in bisexual and parthenogenetic Strophosoma weevils (Coleoptera: Curculionidae)

It has been postulated that parthenogenesis in weevil species is of hybrid origin, but some have speculated that Wolbachia infection plays a role through the modification of host breeding systems. Here we focus on Strophosoma weevils, which are known to be pests in young forest stands. Using molecular data, we investigated the diversity of the two most common Strophosoma species in Europe: S. capitatum, which reproduces bisexually, and S. melanogrammum, which is parthenogenetic. Also researched were their associations with the endosymbiotic bacterium Wolbachia. These species of weevil were found to be clearly distinguishable based on their mitochondrial DNA, with the bisexual taxa being more diverse. However, the nuclear DNA divergence of the two species was very low, and the parthenogenetic taxon was found to be heterozygous. Wolbachia infection was detected in all individuals of the S. melanogrammum populations and less than half of the S. capitatum populations. Moreover, multiple Wolbachia strains were found in both taxa (two in the former and three in the latter). The results of this research suggest that parthenogenesis in this genus is of hybrid origin and that Wolbachia could have played a role in speciation of these weevils.