Host-plant dependent population genetics of the invading weevil Hypera postica.

Population genetics of invading pests can be informative for understanding their ecology. In this study, we investigated population genetics of the invasive alfalfa weevil Hypera postica in Fukuoka Prefecture, Japan. We analyzed mitochondrial tRNALeu-COII, nuclear EF-1α gene fragments, and Wolbachia infection in relation to three leguminous host plants: Vicia angustifolia, Vicia villosa, and a new host Astragalus sinicus cultivated as a honey source and green manure crop. A parsimony network generated from mitochondrial gene sequences uncovered two major haplotypic groups, Western and Egyptian. In contrast to reported Wolbachia infection of the Western strain in the United States, none of our analyzed individuals were infected. The absence of Wolbachia may contribute to the stable coexistence of mitochondrial strains through inter-strain reproductive compatibility. Hypera postica genetic variants for the mitochondrial and nuclear genes were associated neither with host plant species nor with two geographic regions (Hisayama and Kama) within Fukuoka. Mitochondrial haplogroups were incongruent with nuclear genetic variants. Genetic diversity at the nuclear locus was the highest for the populations feeding on V. angustifolia. The nuclear data for A. sinicus-feeding populations indicated past sudden population growth and extended Bayesian skyline plot analysis based on the mitochondrial and nuclear data showed that the growth of A. sinicus-feeding population took place within the past 1000 years. These results suggest a shorter history of A. sinicus as a host plant compared with V. angustifolia and a recent rapid growth of H. postica population using the new host A. sinicus.

Evolutionary diversification of bruchine beetles: climate-dependent traits and development associated with pest status.

A number of insect species infest human households and stored foods and products, leading to their designation as pests. Until recently, little was known about the factors driving the evolution of pests that feed on stored dry foods. Here, I review the effects of changes in climate and species interactions on the evolution and ecology of beetles that feed on dried seeds/grains. My review focuses on evidence that the host utilization by part of the species in the subfamily Bruchinae (Chrysomelidae) is a preadaptation for utilizing stored dry seeds and grains, thus leading to their status as a pest. These and other stored product pest beetles retain a higher percentage of water in their body, relative to the water content of their diet, than beetles that feed on fresh crops. I review the studies that have documented adaptation, acclimation and polyphenetic response to high temperatures and desiccation and/or made direct comparisons between these traits between developmental stages, populations and among higher taxonomic groups. Finally, I review evidence for the effects of environmental change on insect host-parasitoid and competitor assemblages.

Evolutionary diversification of the bean beetle genus Callosobruchus (Coleoptera: Bruchidae): traits associated with stored-product pest status.

Despite the fact that many plant-feeding insects are pests, little effort has been made to identify key evolutionary trait transitions that allow taxa to acquire or lose pest status. A large proportion of species in the genus Callosobruchus are economically important pests of stored, dry postharvest beans of the tribe Phaseoleae. However, the evolution of this feeding habit is poorly understood. Here, we present a reconstruction of the phylogeny of the Asian and African Callosobruchus based on three mitochondrial genes, and assess which traits have been associated with the evolutionary origin or loss of ability to reproduce on dry beans. Our phylogenetic analysis showed that species group into the chinensis and the maculatus clades, which are also supported by genital morphology, and an additional paraphyletic group. Ancestral ability to use dry beans has been lost in the chinensis clade but acquired again in C. chinensis. Dry-bean use and host-plant use were both phylogenetically constrained and transitions in the two were significantly correlated. Host shifts from the subtribe Phaseolinae to Cajaninae were more common than the reverse and were more likely in species using young beans. The ability to use dry beans was more likely gained when using Phaseolinae hosts and promoted habitat shifts from tropical to temperate regions. Adaptation to arid climate was also associated with the ability to reproduce on dry beans and on Phaseolinae. Thus, our analysis suggests that physiological adaptations to an arid climate and to Phaseolinae hosts both render beetles predisposed to become pests of cultivated beans.

Single-locus complementary sex determination absent in Heterospilus prosopidis (Hymenoptera: Braconidae).

In the haplodiploid Hymenoptera, haploid males arise from unfertilized eggs, receiving a single set of maternal chromosomes while diploid females arise from fertilized eggs and receive both maternal and paternal chromosomes. Under single-locus complementary sex determination (sl-CSD), sex is determined by multiple alleles at a single locus. Sex locus heterozygotes develop as females, while hemizygous and homozygous eggs develop as haploid and diploid males, respectively. Diploid males, which are inviable or sterile in almost all cases studied, are therefore produced in high frequency under inbreeding or in populations with low sex allele diversity. CSD is considered to be the ancestral form of sex determination within the Hymenoptera because members of the most basal taxa have CSD while some of the more derived groups have other mechanisms of sex determination that produce the haplo-diploid pattern without penalizing inbreeding. In this study, we investigated sex determination in Heterospilus prosopidis Viereck, a parasitoid from a relatively primitive subfamily of the Braconidae, a hymenopteran family having species with and without CSD. By comparing sex ratio and mortality patterns produced by inbred and outbred females, we were able to rule out sl-CSD as a sex determination mechanism in this species. The absence of sl-CSD in H. prosopidis was unexpected given its basal phylogenetic position in the Braconidae. This and other recent studies suggest that sex determination systems in the Hymenoptera may be evolutionary labile.

Habitat-related mtDNA polymorphism in the stored-bean pest Callosobruchus chinensis (Coleoptera: Bruchidae).

The genetic diversity of populations of the azuki bean beetle, Callosobruchus chinensis (Linnaeus) from natural, pre-harvest and post-harvest sites, was investigated to understand population structure and gene flow. A 522-bp fragment of the mitochondrial gene COI was sequenced for eight populations of C. chinensisfrom Japan, Korea and Taiwan collected from different habitats. Six haplotypes were detected, one of which, U1, occurred most frequently and widely. The following hypotheses were tested as a cause of the wide distribution of haplotype U1; (i) topographical separation (by national boundaries), (ii) host plant species, and (iii) habitat type (natural, pre-harvest crop, or post-harvest storage). Categorization of collection sites by country or by host species did not yield differences in the occurrence of haplotype U1, but habitat type did. Populations utilizing cultivated post-harvest hosts that were mass stored were highly likely to be the common haplotype, whereas host plants in natural habitats away from agriculture were utilized by populations with locally characteristic haplotypes. Sampling of commercial beans for quarantine and export purposes indicated that gene flow in C. chinensis was largely unidirectional into Japan at the present time.

Description of the soybean pod gall midge, Asphondylia yushimai sp. n. (Diptera: Cecidomyiidae), a major pest of soybean and findings of host alternation.

The soybean pod gall midge is an important pest of soybean in Japan and is known to occur also in Indonesia and China. This gall midge is described from Japan as Asphondylia yushimai sp. n. and is clearly distinguished from its congeners by the arrangement of the lower frontal horns of the pupa and the sequence of the mtDNA COI region. It is concluded that Prunus zippeliana Miquel is a winter host of the soybean pod gall midge since haplotypes of the soybean pod gall midge coincide with those of the Prunus fruit gall midge that produces fruit galls on P. zippeliana. In addition, phenological and distributional information on the two gall midges and on their host plants supports the identification of the winter host. In Japan, the soybean pod gall midge overwinters as a first instar in the fruit galls on P. zippeliana and emerges as an adult from the galls in May. In summer and autumn, the soybean pod gall midge has two or more generations in the pods of soybean, Glycine max (L.) Merrill or wild fabaceous and caesalpiniaceous plants. Thus host alternation by A. yushimai is confirmed. This is the second finding of host alternation by a species of Asphondylia, the first instance being that of Asphondylia gennadii (Marchal) in Cyprus.

Immunohistochemical demonstration of the gap junctional protein connexin 32 and proliferating cell nuclear antigen in glutathione S-transferase placental form-negative lesions of rat liver induced by diethylnitrosamine and clofibrate.

The distributions of a gap junctional protein, connexin 32 (cx 32), and proliferating cell nuclear antigen (PCNA) were examined immunohistochemically in glutathione S-transferase placental form (GST-P)-negative foci, induced in rat liver by initiation with diethylnitrosamine (DEN, 200 mg/kg) followed by promotion with clofibrate (1% in diet) in an in vivo medium-term assay system for hepatocarcinogenesis. The results were compared to those in GST-P-positive foci induced by DEN alone. The treatment with clofibrate caused the appearance of GST-P-negative foci, increased in size as compared to GST-P-positive foci in the same liver or induced by the DEN alone. The proportion of PCNA-positive hepatocytes in GST-P-negative foci was significantly higher than in the surrounding parenchyma, indicating increased cell proliferation. The numbers of cx 32-positive spots per hepatocyte in GST-P-negative foci were clearly decreased, reaching 65.4% at week 20 and 51.8% at week 30 of values for surrounding normal hepatocytes. In GST-P-positive foci induced by DEN, only a slight decrease (80%) was observed at week 8. These findings show that a positive association between the sustained inhibition of gap junctional intercellular communication and increased cell proliferation of GST-P-negative foci in Fischer-344 male rats induced with DEN and promoted with clofibrate.

Benarthin: a new inhibitor of pyroglutamyl peptidase. III. Synthesis and structure-activity relationships.

Benarthin, a new inhibitor of pyroglutamyl peptidase (PG-peptidase), has been isolated from the culture filtrate of Streptomyces xanthophaeus MJ244-SF1. The structure of benarthin has been determined to be L-(2,3-dihydroxybenzoyl)arginyl-L-threonine. This structure was confirmed by the total synthesis of benarthin. Moreover, we synthesized benarthin derivatives to obtain information on the relationship between structure and inhibitory activity. The results indicated that the catechol group of benarthin is the essential moiety for the inhibition of PG-peptidase.

[Scanning electron microscopic study of penetrability of sealants in relation to fissure morphology of permanent premolars in humans]. / Rasterelektronenmikroskopische Studie über die Penetrationsfähigkeit von Versiegelungsmitteln in Abhängigkeit von der Fissurenmorphologie bleibender menschlicher Prämolaren.

In the work presented here, the morphological types of the fissure system in permanent human premolars are established, their average depth and width as well as the penetration capacity of fissure in relation to the morphological type of the fissure established (V, U, Y1, Y2). The largest average fissure depth was yielded by the Y2-configuration, the lowest by the V-type. The largest average entrance width was shown by the V-type, the lowest by the Y2-type. A total of 71% of the cases showed a complete filling of the fissure pattern by the sealing matter. All types of V- and U-fissures were totally filled up. With the Y1-type there is a total filling up in 60.7-88.1% of the cases, with the Y1 type in 23.6-57.6% of the cases to be expected. The penetration capacity of the sealer is in a certain correlation to the width of the fissure entrance and the fissure depth.