Occurrence of Wolbachia in central European weevils: correlations with host systematics,ecology, and biology

We studied the occurrence of Wolbachia in relation to the systematics, ecology, and biology of 40 weevil species from central Europe. Identification of Wolbachia supergroups and phylogeny was performed on the basis of 16S rDNA, ftsZ, wsp, and hcpA sequences. Sixteen species (40%) were infected by Wolbachia. Six of these possess only supergroup A (15% of all studied species, 37.5% of the infected species), and four harbored only supergroup B (10 and 25%, respectively). Six species were infected by both supergroups A and B or their genomes harbored parts of these two supergroups (15 and 37.5%, respectively). No differences between Wolbachia supergroup frequencies were detected. There was almost no correlation between Wolbachia phylogeny and host systematics and phylogeny at the level of subfamily and tribe, because the representatives of both supergroups were detected in all the studied multi‐species tribes. Wolbachia strains were probably inherited from a common ancestor only in the case of the genus Strophosoma, where two of three analyzed species possessed bacteria which are genetically very close in all the studied genes. There was also only limited congruence between phylogenies obtained from the four studied genes. These results suggest horizontal transmission of Wolbachia strains between species and recombination events between different strains. A significant correlation was detected between infected and uninfected species in relation to mobility (flying species were 2× more frequently infected than non‐flying species), foraging (polyphagous species were 2.5× less frequently infected than mono‐ or oligophagous species), and reproductive mode (parthenogenetic weevils were infected nearly 2× as often as bisexuals). No differences were detected between mesophilous and xerothermophilous species, nor between those inhabiting open areas vs. arboreal species. However, these results might have been influenced by common ancestry among the studied weevils. Because weevils include many plant pests of economic importance, it is possible to use these data in developing alternative, biology‐based strategies for controlling them.     

New data on the cytology of parthenogenetic weevils (Coleoptera,Curculionidae)

Parthenogenesis and, in particular, polyploidy are rare in animals. A number of cases, known among weevils, represent apomictic parthenogenesis-a reproductive mode in which eggs undergo one maturation division, the chromosomes divide equationally, and no reduction takes place. Among parthenogenetic weevils there are two diploids, 48 triploids, 18 tetraploids, six pentaploids, three hexaploids and one decaploid. Eight examined parthenogenetic species are triploids with 33 chromosomes of different morphology, confirming that triploidy is the most common level of ploidy in weevils. The karyotypes are heterogeneous with the presence of meta-, submeta-, subtelo- and acrocentric chromosomes. The C-banding method showed that only two species possess a large amount of heterochromatin visible as a band around the centromere during mitotic metaphase. This agrees with observations that weevils are characterized by a small amount of heterochromatin, undetectable in metaphase plates after C-banding. In three species an atypical course of apomictic oogenesis occurs with stages similar to meiosis, in which chromosomes form bivalents and multivalent clusters. This association of chromosomes probably represents the remnants of meiosis, although these events have nothing to do with recombination. The results support the hypothesis that the evolution of apomictic parthenogenesis in weevils has proceeded through a stage of automixis.     

Variable host phenology does not pose a barrier to invasive weevils in a northern hardwood forest

• 1 A suite of invasive weevils has established in hardwood forests of the North American Great Lakes Region. We quantified patterns of host availability and the capacity of adults to succeed in a system with high host variability both within and between seasons in Michigan, U.S.A.
• 2 We quantified phenological development of foliage on three host species [sugar maple, Acer saccharum Marshall; ironwood, Ostrya virginiana (Mill.) K. Koch; and raspberry, Rubus spp.]. We estimated adult abundance using emergence traps and sweep net sampling over 3 years, and compared field host associations with laboratory choice assays.
• 3 Host plant phenology varied among species, between years, and in their interactions. The four most common weevils, Phyllobius oblongus (L.), Polydrusus sericeus (Schaller), Barypeithes pellucidus (Boheman) and Sciaphilus asperatus (Bonsdorff), emerged in early to mid‐June, in approximately that order. After emergence, each species showed evidence of host preference based on their abundances on foliage. Overall, P. oblongus and B. pellucidus were most prevalent on sugar maple, P. sericeus was most prevalent on ironwood, and S. asperatus was relatively evenly distributed. Laboratory choice tests with P. oblongus and P. sericeus confirmed these preferences.
• 4 These four invasive species comprised over 99% of all 12 845 weevils obtained, suggesting displacement of native species. The optimal sampling methods varied among weevil species.
• 5 These invasive weevils contend with the highly variable conditions of their environment, and also potential phenological asynchrony, via relatively late emergence, even at the cost of lower host quality. Annual variation is greater for numbers of adults than larvae, suggesting that mortality of late instars or pupae is particularly important.

     

A new species of Polydrusus (Polydrusus) Germar (Coleoptera:Curculionidae) from the Kurdistan region of Iraq

Polydrusus (s. str.) akreanus sp. n. is a new record of Curculionidae found in Iraqi Kurdistan. The new species is described, illustrated and compared with Polydrusus (s. str.) kadleci Borovec & Germann, 2013 known from Turkey and Iran, which is morphologically similar to the new species.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:9FDC3C5B-6854-4DEF-BDF6-EE6809F82DEE     

Feeding by short-snouted weevils on seedlings of seven tree species planted beneath Norway spruce at differing stand densities

1 Short-snouted weevils, including Strophosoma spp. and related species, may damage tree seedlings. We investigated the damage caused by these weevils feeding on seedlings of seven tree species planted in clear-cuts and under shelterwoods with three densities (control, dense, and sparse).
2 There were no pronounced differences in damage caused by short-snouted weevils in the various shelterwood densities. Most feeding occurred in the clear-cuts during the first year, whereas more seedlings were damaged in the shelterwoods of all densities in the second year. In the third year, virtually no feeding occurred in either the clear-cuts or shelterwoods. We cannot explain this pattern of damage, but a fallow period of 2 years seems to prevent short-snouted weevil damage.
3 We determined the general feeding preferences for short-snouted weevils to be cherry, lime > beech, oak, spruce > maple, ash. However, although Strophosoma mellanogrammum [Correction added after online publication 8 December 2008: Strophosoma melanogrammum corrected to Strophosoma mellanogrammum ] was observed feeding on seedlings, no full short-snouted weevil inventory was conducted, so caution must be exercised when drawing conclusions from this study regarding weevil damage patterns and feeding preferences.
4 Short-snouted weevils can sometimes occur in large numbers and may destroy entire reforestation projects, but in our study their influence on seedling growth and survival was minor.     

Molecular evidence for multiple infections of a new subgroup of Wolbachia in the European raspberry beetle Byturus tomentosus

Wolbachia, a group of maternally inherited intracellular parasitic bacteria, alter host reproduction, including the induction of thelytokous parthenogenesis, feminization of genetic males, son killing and, most commonly, the induction of cytoplasmic incompatibility (CI), in a diverse array of arthropods. CI can result in infertility and has attracted attention because of its potential in biological control and as an agent in speciation. Although there has been some analysis of overall infection rates in arthropods and within individual insect orders, there has been little exploration of within-species variation. In this study, primers specific for the ftsZ gene of Wolbachia were used to amplify it from different geographical samples of the European raspberry beetle (Byturus tomentosus), confirming the presence of Wolbachia. More than 99% of UK individuals were found to be infected with Wolbachia and 97% of these B. tomentosus beetles harboured multiple infections. Preliminary analysis of B. tomentosus beetles from continental European populations revealed a lower level of infection (24%) than those from the UK. Phylogenetic analysis using the ftsZ DNA sequences places Wolbachia from B. tomentosus into a new clade (Abt) within the A division, with some revisions to the existing Wolbachia phylogeny.     

高温冲击对沃尔巴克氏体(Wolbachia)诱导孤雌产雌的丽蚜小蜂(Encarsia formosa)生殖和发育的影响

研究了持续高温(31℃恒温)和高适温交替(白天31℃/夜间25℃变温)条件对感染沃尔巴克氏体(Wolbachia)的丽蚜小蜂生殖和发育的影响.结果发现在持续高温条件下,丽蚜小蜂的生殖力和羽化率降低、寿命缩短、后代雄性比例增加,丽蚜小蜂从F1代开始产生雄性后代,且雄性比例在45%以上,F2代雄性比例达到最高值,表明高温冲击会对丽蚜小蜂的控害潜能产生不利的影响,因此在丽蚜小蜂的商业生产和田间应用中要注意环境温度,避免因高温带来的损失.在31℃恒温条件下连续培养3代或6代再转入25℃培养,丽蚜小蜂雄性后代比例和沃尔巴克氏体在丽蚜小蜂雌性群体中的感染率都能够很快恢复到高温处理前的水平.说明沃尔巴克氏体对环境变化有一个自动调节和适应的过程.变温条件下丽蚜小蜂从F2代开始产生雄性后代,但雄性后代比例较低(13%),表明短期高温冲击对丽蚜小蜂的生殖方式影响不大,但是短期高温冲击如果持续作用就会产生积累效应,影响丽蚜小蜂的后代性别.     

孤雌产雌生殖品系松毛虫赤眼蜂产卵强度对Wolbachia诱导的其生殖表型的影响

[目的]松毛虫赤眼蜂Trichogramma dendrolimi是一种用于鳞翅目害虫生物防治的重要卵期寄生蜂.本研究旨在明确孤雌产雌生殖品系松毛虫赤眼蜂的产卵强度对其体内Wolbachia滴度及Wolbachia诱导的孤雌产雌生殖表型的影响.[方法]在室内调查了3个处理组松毛虫赤眼蜂雌蜂不同产卵强度(每日仅1 h供寄...     

Altered GAI activity of hybrid aspen has minimal effects on the performance of a polyphagous weevil,Polydrusus sericeus

Genetically modified plants can have unintended effects on herbivores, even when the transgene is not explicitly devised for pest protection. These effects may lead to altered ecological relationships in areas where transgenic plants are deployed. We tested several genetically‐modified hybrid aspen clone INRA 717‐IB4 [Populus tremula L. ×P. alba L. (Salicaceae)] lines expressing transgenic constructs with altered gibberellic acid expression for their effects on a polyphagous insect, Polydrusus sericeus (Schaller) (Coleoptera: Curculionidae). Longevity, egg production, and leaf consumption were measured in laboratory assays. Only male longevity was negatively affected by foliage from genetically modified trees, and in no case was oviposition or leaf consumption significantly altered. The importance of males in population dynamics varies among species, but we do not have evidence it is a major driver in this system. Contrary to our hypothesis of increased performance on modified foliage, adult P. sericeus were rarely affected by GM foliage, suggesting that not all genetic modifications that alter secondary metabolism in plants will necessarily have a strong effect on specific insect‐plant relations, supporting the view that evaluations continue to require case by case analysis.     

昆虫共生细菌Wolbachia的研究进展

Wolbachia是广泛分布在节肢动物生殖组织的一类细胞质遗传的细菌,它们能通过多种机制调节寄生的生殖,包括诱导细胞质不亲和,孤雌生殖和遗传上的雄性雌性化,目前对这些微生物的研究已取了可喜的进展,通过主要综述Wolbachia的分布,功能,系统发育,多样性及时空动态,也讨论了将来的研究方向     

Movement of adult pecan weevils Curculio caryae within pecan orchards

1 The pecan weevil Curculio caryae (Horn) (Coleoptera: Curculionidae) is an indigenous pest of pecan Carya illinoinensis (Wangenh.) K. Koch, in North America. Understanding the movement of this pest from the orchard floor to host trees could lead to pest management practices that exploit weevil behaviour and thus reduce insecticide application to the entire orchard canopy. Furthermore, no information exists on diel periodicity of pecan weevil movement. 2 Movement of adult pecan weevils crawling and flying to the host trunk, flying to the host canopy, crawling within the host canopy and flying between host trees was studied using four types of passive traps over four seasons. Each type of trap was used to capture weevils at different locations on or near the tree and to discriminate flying versus crawling behaviour. 3 More pecan weevils crawl to the trunk than fly and a proportion of the population flies directly from the orchard floor into the pecan canopy. The majority of this movement occurs at dusk. 4 The vertical distribution of weevils was generally uniform throughout the canopy but more weevils were captured in suspended traps nearest tree tops, rather than traps near the ground, when flying between trees and this was significantly so for two of 4 years. 5 The results of the present study are contrary to previous reports suggesting that most adult pecan weevils fly to the pecan trunk after emergence from the soil; however, our results did indicate that a proportion of the population flies directly from the orchard floor into the pecan canopy and thus would circumvent strategies that attempt to control weevils moving up the trunk.     

Transgressing Wallace's Line brings hyperdiverse weevils down to earth

Wallace's Line, located in the heart of the Indo-Australian archipelago, has historically been hypothesized to strongly inhibit dispersal. Taxa crossing this barrier are confronted with different biota of Asian or Australian origin, respectively, but the extent to which these conditions have affected the evolution of the colonizing lineages remains largely unknown. We examined the potential correlations of body size, lifestyle and biogeographical distribution in the weevil genus Trigonopterus. These beetles are highly diverse both on foliage and in litter east of Wallace's Line but occur exclusively in leaf litter in the west. Based on a comprehensive, dated phylogeny of 303 species, we inferred nine crossing events of Wallace's Line, all from east to west. Five previously foliage-dwelling lineages changed their lifestyle to leaf litter habitats after crossing this barrier. Our results indicate that dispersal is not more likely in edaphic lineages, but rather that abiotic and/or biotic factors may be responsible for the exclusive leaf litter habitat of Trigonopterus in Sundaland. This includes differences in climate, and the different predatory faunas of Australia-New Guinea, Wallacea and Sundaland. A mimicry complex in New Guinea with Trigonopterus species as presumable model may be of relevance in this context.     

Effects and implications of antibiotic treatment on Wolbachia-infected vine weevil (Coleoptera: Curculionidae)

1 The parthenogenetic weevil Otiorhynchus sulcatus was collected from five geographical locations in the U.S.A. All weevils from each location were infected by Wolbachia belonging to supergroup B. 2 We hypothesized that treatment with tetracycline, which has been used to clear Wolbachia infection, would influence the reproduction of Wolbachia‐infected parthenogenetic O. sulcatus females. Tetracycline treatment of preovipositional O. sulcatus females specifically inhibited egg hatching but had no effect relative to controls on any other physiological trait. 3 Treatment with gentamicin, which reportedly has no effect on Wolbachia infection but is indistinguishable from tetracycline in inhibiting protein synthesis of other bacterial genera, did not influence egg hatching. 4 These findings strongly suggest that the inhibition of egg development results from the antibiotic effect on Wolbachia rather than by direct toxic effects on O. sulcatus physiology. 5 We speculate that Wolbachia may be necessary for normal development of O. sulcatus eggs and discuss the implications of these findings for O. sulcatus ecology.     

EVOLUTION OF ASEXUALITY VIA DIFFERENT MECHANISMS IN GRASS THRIPS (THYSANOPTERA: Aptinothrips)

Asexual lineages can derive from sexual ancestors via different mechanisms and at variable rates, which affects the diversity of the asexual population and thereby its ecological success. We investigated the variation and evolution of reproductive systems in Aptinothrips, a genus of grass thrips comprising four species. Extensive population surveys and breeding experiments indicated sexual reproduction in A. elegans, asexuality in A. stylifer and A. karnyi, and both sexual and asexual lineages in A. rufus. Asexuality in A. stylifer and A. rufus coincides with a worldwide distribution, with sexual A. rufus lineages confined to a limited area. Inference of molecular phylogenies and antibiotic treatment revealed different causes of asexuality in different species. Asexuality in A. stylifer and A. karnyi has most likely genetic causes, while it is induced by endosymbionts in A. rufus. Endosymbiont‐community characterization revealed presence of Wolbachia, and lack of other bacteria known to manipulate host reproduction. However, only 69% asexual A. rufus females are Wolbachia‐infected, indicating that either an undescribed endosymbiont causes asexuality in this species or that Wolbachia was lost in several lineages that remained asexual. These results open new perspectives for studies on the maintenance of mixed sexual and asexual reproduction in natural populations.     

The material ancestry and approximate age of parthenogenetic species of Caucasian rock lizards (Lacerta: Lacertidae)

Restriction enzymes were used to assay variation among mitochondrial DNAs from parthenogenetic and sexual species of Lacerta. This permitted identification of the sexual species that acted as the maternal parent of the various hybrid-parthenogenetic lineages. Lacerta mixta was the maternal parent for both L. dahli and L. armeniaca, L. valentini was the maternal parent for L. uzzelli, and L. raddei was the maternal parent of L. rostombekovi. The maternal ancestry of L. unisexualis is not as clear. The sample of L. nairensis was very similar to one from a population of L. raddei and either species could be the maternal parent of L. unisexualis. The parthenogenetic species all had very low nucleotide diversity in absolute terms and in comparison to their sexual relatives. The close similarity between mtDNAs from the parthenogenetic species and their respective sexual maternal ancestor species provides strong evidence for the recent origin of the parthenogens. The low diversity of the parthenogens indicates that few females were involved in their origins; the maternal parents of L. dahli and L. armeniaca could have come from a single population. The patterns of mtDNA variation in Lacerta are very similar to those in Cnemidophorus and Heteronotia, establishing recent and geographically restricted origins as a general feature of parthenogenetic lizards.     

Overwintering of annual bluegrass weevils, Listronotus maculicollis, in the golf course landscape

Annual bluegrass weevil, Listronotus maculicollis (Dietz) (Coleoptera: Curculionidae), adults overwinter in protected areas but their life cycle is completed on highly maintained turfgrass. To better target control tactics on affected golf courses, we need to understand the relationship between overwintering and developmental habitats. Our objectives were to identify factors that influence overwintering site selection and to gather evidence of directional movement. Surveys of natural field populations were conducted in early spring over 2 years to test how abundance of overwintered adults depends on microhabitat (surface composition) and distance from the developmental habitat. The influence of microhabitat on overwintering preference and success was further tested in a multiple‐choice and no‐choice field experiment by relocating overwintering weevils into experimental arenas where four microhabitats were presented together or singly. The timing and direction of dispersal by walking adults was assessed using paired linear pitfall traps. Results showed that adults could overwinter up to 60 m from the fairway and 10 m into the woods. They were most abundant near the tree line; none were detected within 5 m of the fairway. Microhabitat had a significant effect on abundance in 1 year, being highest in mixed tree litter followed by moss, high‐cut grass, and pine litter. Under multiple‐choice conditions, high‐cut grass was preferred over low‐cut grass and leaf litter, followed by pine litter. Pitfall trap captures showed a peak of activity in the spring, and at one site this was directional toward the fairway. There was no directionality or increase in activity in the fall. Based on these results, a new conceptual model of flux between habitats is proposed based on orientation of flying adults to defined tree lines. Defining this behavior will strengthen our ability to target control tactics in space and time against this major turf pest.     

Microsatellite and morphological analysis of population structure in the parthenogenetic freshwater snail Melanoides tuberculata: insights into the creation of clonal variability

The distribution of variability was studied at various geographical scales in the tropical freshwater snail Melanoides tuberculata, in order to analyse the role of factors shaping this distribution, including the mating system and population dynamics. This parthenogenetic polyploid species reproduces mainly asexually, with males occurring at low frequency. About 800 individuals (38 sites) were sampled from Africa and the Middle East, where the species originated, and from recently colonized habitats in South and Central America, and especially the island of Martinique. We first described variation of general aspects and ornamentation of the shells. This analysis confirms the existence of discrete morphs. Second, individuals were studied at three microsatellite loci, showing that each morph is a genetic clone with some minor variation compatible with models of microsatellite evolution. The genetic analysis also showed much more variation within than between clones. However, two populations from Africa exhibited a large amount of variability, and a mixture of sexual and asexual reproduction might explain these genetic patterns. The worldwide distribution of variability is, therefore, compatible with the African origin of the species, and the introduction of a few clones in other parts of the world. These results also suggest that the distribution of variability in Martinique is influenced by flooding events, and that two morphs from Martinique can be interpreted as hybrids between two pre-existing morphs, based on morphological, genetic and geographical arguments.     

Genetic diversity and Wolbachia infection of the Drosophila parasitoid Leptopilina clavipes in western Europe

Wolbachia are maternally transmitted bacteria that alter their arthropod hosts' reproduction in various ways, including parthenogenesis induction (PI). Wolbachia-induced parthenogenesis can have drastic effects on the genetic structure of its host because it potentially reduces populations to clones without genetic exchange. However, Wolbachia-induced parthenogenesis does not inevitably result in a reduction of genetic variation of infected populations vs. uninfected populations, because the parthenogenetic populations are initially derived from uninfected populations and can thus show similar genetic variation. Here we investigate these issues in infected and uninfected populations of the Drosophila parasitoid Leptopilina clavipes in western Europe. Wasps from 19 sites in the Netherlands, France and northern Spain were screened for Wolbachia and analysed using amplified fragment length polymorphism (AFLP) markers. All the populations from the Netherlands and mid-France were infected with the same two strains of Wolbachia, whereas populations from the Pyrenees were not infected. The infected and uninfected populations show identical levels of genetic variation, but have clearly diverged genetically, indicating the presence of a barrier that prevents gene flow. Within the infected wasps two distinct genotypes were found at multiple localities, indicating the coexistence of multiple clones. The conditions promoting clonal coexistence in L. clavipes are discussed.     

The evolution of sexual and parthenogenetic Warramaba: a window onto Plio–Pleistocene diversification processes in an arid biome

Environmental changes over the Plio‐Pleistocene have been key drivers of speciation patterns and genetic diversification in high‐latitude and mesic environments, yet comparatively little is known about the evolutionary history of species in arid environments. We applied phylogenetic and phylogeographic analyses to understand the evolutionary history of Warramaba grasshoppers from the Australian arid zone, a group including sexual and parthenogenetic lineages. Sequence data (mitochondrial COI) showed that the four major sexual lineages within Warramaba most likely diverged in the Pliocene, around 2–7 million years ago. All sexual lineages exhibited considerable phylogenetic structure. Detailed analyses of the hybrid parthenogenetic species W. virgo and its sexual progenitors showed a pattern of high phylogenetic diversity and phylogeographic structure in northern lineages, and low diversity and evidence for recent expansion in southern lineages. Northern sexual lineages persisted in localized refugia over the Pleistocene, with sustained barriers promoting divergence over this period. Southern parts of the present range became periodically unsuitable during the Pleistocene, and it is into this region that parthenogenetic lineages have expanded. Our results strongly parallel those for sexual and parthenogenetic lineages of the gecko Heteronotia from the same region, indicating a highly general effect of Plio‐Pleistocene environmental change on diversification processes in arid Australia.