Global genetic diversity,lineage distribution,and Wolbachia infection of the alfalfa weevil Hypera postica (Coleoptera: Curculionidae)

The alfalfa weevil (Hypera postica) is a well‐known example of a worldwide‐distributed pest with high genetic variation. Based on the mitochondrial genes, the alfalfa weevil clusters into two main mitochondrial lineages. However, there is no clear picture of the global diversity and distribution of these lineages; neither the drivers of its diversification are known. However, it appears likely that historic demographic events including founder effects played a role. In addition, Wolbachia, a widespread intracellular parasite/symbiont, likely played an important role in the evolution of the species. Wolbachia infection so far was only detected in the Western lineage of H. postica with no information on the infecting strain, its frequency, and its consequences on the genetic diversity of the host. We here used a combination of mitochondrial and nuclear sequences of the host and sequence information on Wolbachia to document the distribution of strains and the degree of infection. The Eastern lineage has a higher genetic diversity and is found in the Mediterranean, the Middle East, Eastern Europe, and eastern America, whereas the less diverse Western lineage is found in Central Europe and the western America. Both lineages are infected with the same common strain of Wolbachia belonging to Supergroup B. Based on neutrality tests, selection tests, and the current distribution and diversification of Wolbachia in H. postica, we suggested the Wolbachia infection did not shape genetic diversity of the host. The introduced populations in the United States are generally genetically less diverse, which is in line with founder effects.     

Capacity of Japanese Asobara species (Hymenoptera; Braconidae) to parasitize a fruit pest Drosophila suzukii (Diptera; Drosophilidae)

Drosophila suzukii is a pest of soft fruit such as cherry, strawberry or blueberry and recently colonized North America and Europe from Asia. In this study, we assessed the utility of Japanese Asobara species as agents for the biological control of this pest species by examining their host use in nature and their capacity to parasitize this pest species. From Japan, eight Asobara species including putative three undescribed species were found; Asobara japonica was recorded from all over Japan, Asobara tabida from high altitude areas in central and northern Japan, Asobara rossica and Asobara rufescens from central to northern Japan, three undescribed species from central to western or southern Japan and Asobara pleuralis from a subtropical island of Japan. Among them, an undescribed species Asobara sp. TK1 may be useful as an agent for the biological control because it was recorded only from D. suzukii. All of the remaining seven species were generalists mainly using drosophilid species associated with fermenting fruits, and four of them had no or very low abilities to parasitize D. suzukii, indicating that these seven species are not or less appropriate as agents for biological control.     

<Emphasis Type="Italic">Psathyrella turcosomarginata</Emphasis>, a new species with cheilocystidia possessing mucoid deposits staining bluish green in ammonia solution

Psathyrella turcosomarginata is described and illustrated as a new species from Japan (Fukuoka Prefecture, Kyushu). This species is assigned to section Spintrigerae because of its lack of pleurocystidia and basidiome habit. It is characterized by having fairly large basidiomes, a distinct sulcate-striate pileal margin, and cheilocystidia with mucoid deposits that stain bluish green in ammonia solution.     

A new record of the tobacco thrips <Emphasis Type="Italic">Frankliniella fusca</Emphasis> (Hinds) (Thysanoptera: Thripidae) from Japan

The tobacco thrips, Frankliniella fusca, which is known as a vector of TSWV and Pantoea ananatis causing center rot of onion, and a serious pest of tobacco, cotton and groundnuts in North America, is newly recorded from the bulbs of Narcissus pseudonarcissus in Honshu, mainland Japan. Two strains were found in Shimane Prefecture. One strain was collected from a bulb produced in Niigata Prefecture in the winter of 2002, and the other was collected from bulbs produced in Fukushima Prefecture in the autumn of 2002. F. fusca can be easily distinguished from other members of this genus in Japan.     

Hybridization and cytoplasmic incompatibility among alfalfa weevil strains

Cross-matings were conducted among eastern, western, and Egyptian alfalfa weevil strains. Fully viable progenies were produced in reciprocal crosses between eastern and Egyptian weevils. The cross between western males and females of eastern or Egyptian strains was incompatible, producing infertile eggs, while the reciprocal cross yielded viable progeny but with a distorted sex ratio, predominantly female. The cause of incompatibility is due to the presence in the western weevil of a rickettsia, which is transmitted through the female parent. Of eight weevil populations surveyed, only the western weevil and a weevil population from the Netherlands harbored the rickettsiae. We conclude that all alfalfa weevil populations in the United States belong to the same species, Hypera postica (Gyllenhal), and that they are potentially interbreeding populations.

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Résumé Des croisements ont été effectués entre 3 lignées d'H. postica et H. brunneipennis. Des descendants totalement viables ont été obtenus par croisements réciproques entre H. postica de Beltsville et H. brunneipennis. Les croisements entre mâles de H. postica de Logan et femelles de H. postica de Beltsville ou de H. brunneipennis ont été incompatibles, produisant des oeufs stériles, tandis que les croisements réciproques donnaient une descendance viable, mais avec un taux sexuel modifié avec prédominance de femelles. La cause de l'incompatibilité est due à la présence d'une rickettsia dans les H. postica de Logan, transmise par la femelle. Des 8 populations examinées, seule celle de Logan et 1 des pays Bas hébergeaient des rickettsia. Nous en concluons que toutes les populations des USA appartiennent à H. postica Gyllenhal, et qu'elles sont toutes potentiellement interfécondes.

     

Comparison of sexual compatibility in crosses between the southern and northern populations of the cabbage beetle Colaphellus bowringi

It is widely accepted that the genetic divergence and reproductive incompat- ibility between closely related species and/or populations is often viewed as an important step toward speciation. In this study, sexual compatibility in crosses between the southern XS population and the northern TA population of the polyandrous cabbage beetle Co- laphellus bowringi was investigated by testing their mating preferences, mating latency, copulation duration, and reproductive performances of post-mating. In choice mating ex- periments, the percentages ofmatings were significantly higher in intra-population crosses than in inter-population crosses. Both isolation index （/） and index of pair sexual isolation （/PSi） indicated partial mating incompatibility or assortative mating in crosses between the two different geographical populations. In single pair mating experiments, XS females in inter-population crosses mated significantly later and copulated significantly shorter than those in intra-population crosses. However, TA females in inter-population crosses mated significantly earlier and copulated longer than those in intra-population crosses, suggesting that larger XS males may enhance heterotypic mating. The lifetime fecundity was highest in XS homotypic matings, lowest in TA homotypic matings, and intermedi- ate in heterotypic rnatings between their parents. The inter-population crosses resulted in significantly lower egg hatching rate and shorter female longevity than intra-population crosses. These results demonstrated that there exist some incompatibilities in premating, postmating-prezygotic, and postzygotic stages between the southern XS population and northern TA population of the cabbage beetle Colaphellus bowringi.     

Tebufenozide resistance is associated with sex‐linked inheritance in Plutella xylostella

The diamondback moth (DBM), Plutella xylostella (L.), is a major pest of cruciferous crops. Tebufenozide, a novel nonsteroidal ecdysone agonist, exhibits good efficacy and has played an increasingly important role in the control of Lepidopteran pests in China. For its resistance management, the genetic basis of tebufenozide resistance was studied using a laboratory selected resistant strain of DBM (resistant ratio, RR = 268). A series of crosses with laboratory susceptible and resistant strains revealed that tebufenozide resistance in this pest was partially biased toward female heredity, with a large difference in RR for F₁ (RR = 29) and rF₁ progeny (RR = 147). The dominance calculated for these 2 cross progeny was ?0.788 and 0.09, respectively. Further analysis showed that the susceptible male and female larvae were similar in their sensitivity to tebufenozide, but the resistant female larvae showed significantly higher resistance than the resistant male larvae. The heredity of tebufenozide resistance in DBM might be linked with the W sex chromosome, which suggested that DBM has the ability to develop high levels of resistance to tebufenozide. This is the first report of sex‐linked inheritance of tebufenozide resistance in P. xylostella (L.).     

Next‐generation transgenic cotton: pyramiding RNAi and Bt counters insect resistance

Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) are extensively cultivated worldwide. To counter rapidly increasing pest resistance to crops that produce single Bt toxins, transgenic plant ‘pyramids’ producing two or more Bt toxins that kill the same pest have been widely adopted. However, cross‐resistance and antagonism between Bt toxins limit the sustainability of this approach. Here we describe development and testing of the first pyramids of cotton combining protection from a Bt toxin and RNA interference (RNAi). We developed two types of transgenic cotton plants producing double‐stranded RNA (dsRNA) from the global lepidopteran pest Helicoverpa armigera designed to interfere with its metabolism of juvenile hormone (JH). We focused on suppression of JH acid methyltransferase (JHAMT), which is crucial for JH synthesis, and JH‐binding protein (JHBP), which transports JH to organs. In 2015 and 2016, we tested larvae from a Bt‐resistant strain and a related susceptible strain of H. armigera on seven types of cotton: two controls, Bt cotton, two types of RNAi cotton (targeting JHAMT or JHBP) and two pyramids (Bt cotton plus each type of RNAi). Both types of RNAi cotton were effective against Bt‐resistant insects. Bt cotton and RNAi acted independently against the susceptible strain. In computer simulations of conditions in northern China, where millions of farmers grow Bt cotton as well as abundant non‐transgenic host plants of H. armigera, pyramided cotton combining a Bt toxin and RNAi substantially delayed resistance relative to using Bt cotton alone.     

Phylogeography of North Atlantic intertidal tardigrades: refugia,cryptic speciation and the history of the Mid‐Atlantic Islands

Aim To analyse the phylogeographical history of intertidal tardigrades in the North Atlantic in order to improve our understanding of geographical differentiation in microscopic organisms, and to understand the potential importance of the Mid‐Atlantic Islands as stepping stones between the American and European coasts of the Atlantic Ocean. Location Twenty‐four localities from the Mid‐Atlantic Islands (Greenland, Iceland and the Faroe Islands) and both sides of the North Atlantic Ocean. Methods A mitochondrial marker (cytochrome c oxidase subunit I) was sequenced from individual tardigrades belonging to the genus Echiniscoides. The existence of cryptic species was detected using generalized mixed Yule coalescence analysis; lineage ages were estimated with relaxed clock methods; and the degree of geographical differentiation was analysed with samova analyses, haplotype networks and Mantel tests. Results Echiniscoides hoepneri, previously known only from Greenland, was recovered throughout the Mid‐Atlantic Islands. The Faroe Islands population was isolated from Greenland and Iceland, but overall genetic variation was low. The morphospecies Echiniscoides sigismundi had high genetic variation and consisted of at least two cryptic species. A northern and a southern species were both recovered on both sides of the Atlantic, but only the northern species was found on the Mid‐Atlantic Islands. The northern species showed signs of long‐term isolation between the Western and Eastern Atlantic, despite the potential of the Mid‐Atlantic islands to act as stepping‐stones. There was no sign of long‐term isolation in the southern species. The Mid‐Atlantic individuals of the northern species were of Eastern Atlantic origin, but Greenland and Iceland showed signs of long‐term isolation. The genetic pattern found in the southern species is not clearly geographical, and can probably be best explained by secondary contact between former isolated populations. Main conclusions North Atlantic intertidal tardigrades from the genus Echiniscoides showed strong geographical differentiation, and the Mid‐Atlantic Islands seemed unimportant as stepping stones across the Atlantic. The geographical variation of the northern species of E. sigismundi suggests post‐glacial recolonization from several refugia.     

Discrimination of two Japanese water pennies,Eubrianax granicollis Lewis and E. ramicornis Kiesenwetter (Coleoptera: Psephenidae), based on laboratory rearing and molecular taxonomy

Two psephenid beetles, Eubrianax granicollis Lewis and E. ramicornis Kiesenwetter, are common species on the main islands of Japan (i.e. Honshu, Shikoku and Kyushu), but diagnostic characters for larval identification are unknown. Two types of field‐collected Eubrianax larvae from Honshu and Kyushu were discriminated based on the distributions of granules on the dorsal surface. These larvae were assigned to E. granicollis and E. ramicornis by comparing them with larvae of the two species obtained via laboratory rearing. The two species were also identified unambiguously on the basis of their mitochondrial cytochrome oxidase subunit I (COI) gene sequences. Larval and pupal morphology are described based on laboratory‐reared specimens.     

Revision and synopsis of the caddisfly genus Dicosmoecus (Trichoptera: Limnephilidae; Dicosmoecinae)

Six species of Dicosmoecus are recognized: the palatus species group of Siberia and Japan [palatus (McL.), obscuripennis Banks, and jozankeanus Mats.)]; and the atripes species group of western montane North America [atripes (Hagen), gilvipes (Hagen), and pallicornis Banks]. D. obscuripennis is re‐established as a valid species distinct from palalus and recorded from the Yukon Territory and Alaska, and also Siberia. Keys are provided for identification of males, females, and larvae. Hypotheses of phylogeny and biogeography are proposed, stating that the palatus and atripes species groups evolved independently in Asia and North America respectively; and that obscuripennis of the palatus group extended its range to North America during the Pleistocene Beringian land connection between the two continents.

Data on food, life cycle, habitat, and distribution are given for the North American species. Most Dicosmoecus appear to be generalized predator‐shredders with robust, toothed mandibles; but fifth instar larvae of D. gilvipes feed mainly by scraping rocks for diatoms, a behaviour which is evidently responsible for eroding the slender blade and weakly formed teeth of the mandible, unique to this species, to a uniform scraping edge. D. gilvipes is further distinctive in usually having a 1‐year life cycle, whereas atripes and the other North American species usually have a life cycle of 2 years.     

Variation in flash speed of Japanese firefly,Luciola cruciata (Coleoptera: Lampyridae), identifies distinct southern “quick‐flash” population on Goto Islands,Japan

Luciola cruciata, a bioluminescent firefly endemic to Japan, communicates with species‐specific flashing patterns. Previous studies reported that flying males possess three distinct flashing frequencies: slow (4 s), intermediate (3 s) and fast (2 s). Our study focused on geographical variations in flashing patterns in the northwestern part of the Kyushu region of southern Japan (including its isolated islands) and their relationship to the mitochondrial COII region of firefly DNA. We found that “quick‐flash (1 s)” fireflies occur in the Goto Islands, at the western tip of Kyushu, and that, although they possess a unique haplotype, they do not differ much genetically from “fast‐flash” fireflies inhabiting mainland Kyushu. In contrast, although fireflies inhabiting the Tsushima and Iki Islands also possess a unique haplotype, their flashing patterns were the same (fast‐flash) as fireflies inhabiting mainland Kyushu. We determined that flash patterns of L. cruciata in Japan should be classified according to four flashing patterns: slow, intermediate, fast and quick.     

Mating behaviour and reproductive output in insecticide‐resistant and ‐susceptible strains of the maize weevil (Sitophilus zeamais)

Insecticide resistance is a broadly recognised and well‐studied management problem resulting from intensive insecticide use, which also provides useful evolutionary models of newly adapted phenotypes to changing environments. Two common assumptions in such models are the existence of fitness costs associated with insecticide resistance, which will place the resistant individuals at a disadvantage in insecticide‐free environments, and the prevalence of random mating among insecticide‐resistant and ‐susceptible individuals. However, cases of insecticide resistance lacking apparent fitness disadvantages do exist impacting the evolution and management of insecticide resistance. Assortative mating, although rarely considered, may also favour the evolution and spread of insecticide resistance. Thus, the possible existence of both conditions in the maize weevil (Sitophilus zeamais), a key pest of stored cereals, led to the assessment of the mating behaviour and reproductive fitness of insecticide‐resistant and ‐susceptible weevil strains and their reciprocal crosses. The patterns of female and male mating choice also were assessed. Although mating behaviour within and between weevil strains was similar without mate choice, mating within the resistant strain led to higher reproductive output than within the susceptible strain; inter‐strain matings led to even higher fertility. Thus, no apparent fitness cost associated with resistance seems to exist in these weevils, favouring the evolution of this phenotype that is further aided by the higher fertility of inter‐strain matings. Mate choice reduced latency to mate and no inter‐strain preference was detected, but female weevils were consistent in their mate selection between 1st and 2nd matings indicating existence of female mating preference among maize weevils. Therefore, if female mate selection comes to favour trait(s) associated with insecticide resistance, higher reproductive fitness will be the outcome of such matings favouring the evolution and spread of insecticide resistance among maize weevil populations reverting into a management concern.     

Size‐dependent growth of individual Atlantic salmon Salmo salar alevins from hatch to first feeding

Variation in egg size, hatch timing and size at hatch, and their influence on individual growth rates of Atlantic salmon Salmo salar alevins up to first feeding were examined in pure strain and hybrid crosses of fish from Scotland and Canada. At the intra‐female, intra‐cross type and inter‐cross type levels, specific growth rates prior to first feed were strongly size dependent, with smaller and later hatching alevins growing significantly faster. The magnitude of this size‐dependent growth was greatest in the hybrid crosses. This resulted in a 40% reduction in the coefficient of variation (c.v. ) in alevin size from post‐hatch to first feeding at the intra‐female level, and a reduction of both intra‐ and inter‐cross differences in alevin sizes in the same period.     

Kin Recognition in the largely Solitary Bee,Manuelia postica (Apidae: Xylocopinae)

The recognition of conspecifics is a central issue to social behaviour. In eusocial hymenopterans, kin recognition has been clearly demonstrated. Manuelia postica is a largely solitary bee species in which larvae develop inside individual cells within a nest and remain isolated from conspecifics until the destruction of partitions by adults. Nestmate recognition in M. postica has been previously demonstrated under experimental conditions. Isolation between individuals during development and nestmate recognition ability in adult females make M. postica an ideal species for testing the occurrence of kin recognition capacity in females. Kin recognition was demonstrated through cross‐fostering field experiments involving the single transfer of recently enclosed larvae, and subsequent laboratory recognition bioassays with emerging females. Results suggest kin recognition occurs through self‐referent phenotype matching. Given the basal position of Manuelia in the phylogeny of the Apidae, kin recognition may represent an ancestral recognition mechanism in Apidae species phylogenetically more derived than M. postica.     

Cold hardiness in the pre‐imaginal stages of the great web‐spinning pine‐sawfly Acantholyda posticalis

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European populations of Diabrotica virgifera virgifera are resistant to aldrin,but not to methyl‐parathion

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Ancient and modern colonization of North America by hemlock woolly adelgid,Adelges tsugae (Hemiptera: Adelgidae), an invasive insect from East Asia

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Effects of admixture in native and invasive populations of <Emphasis Type="Italic">Lythrum salicaria</Emphasis>

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